St. Louis Canyon before dawn

Friday morning a week ago, right in the middle of January, I woke early at Starved Rock State Park. I was housed with a group of my colleagues in the lodge, which is perched at the edge of the long trail paralleling the Illinois River. The trails there mostly overlook the river, with occasional loops down to connect the bluff-top trails with the shoreline trails. They are intersected by sandstone canyons that open into the river, with waterfalls spilling over one ledge after the next. I have been here many times with my family when the boys were younger, and we have hiked these trails in both directions from the lodge numerous times. I had not been here in years.

I headed toward St. Louis Canyon. The first half hour of my walk preceded the dawn, but the trails were as broad and hard as sidewalks, impressed into the soil and easily felt beneath one’s boots. It would be difficult to accidentally veer from the path, which is handy, especially in the dark: four feet off the trail in some places would make for a potentially lethal tumble onto the road or trails below. The ice crusted over the creeks babbling along the sandstone was the color of moonlight. The moon itself was murky behind the clouds, fading into and out of view. I stood on each bridge I crossed and watched the water gurgling beneath the ice, which piled up around the edges of the watercourses and framed the edges of the sandstone ledges where they gave way to the canyon below, where the ravines open up into a rich forest until it tumbled into the broad, slow river.

There was no snow. In the veiled moonlight the leaf litter of white and red and black oaks was quilted together with fallen branches and hop hornbeam leaves to frame the trail. The night before, my colleague Jake had pointed out a black oak that was cracked open below. He guided our attention upward. There, the narrow crown was rotated to lean against the adjacent trunk. The tree trunk had failed, perhaps in a storm, presumably in part because it was hollowed out with rot. At knee level, the bark was twisted and buckled on the outer face, straight on the inside where it was tacked at the base by the bole leaning away from the trail toward the north. I passed this tree now as I walked. All along the ridgetop this dry-mesic oak forest stretched, rimmed by junipers near the edge and white pines on the shoulder of the bluff. No birds were singing, and only the occasional car passed on the road below.

I reached the switchback just before the road at the west end of the trail. It was still dark, but the sky to the east was becoming a lighter shade of gray. The sound of cars rolling by on Highway 178 faded in and then subsided as I followed the creek weaving out of St. Louis Canyon alongside and under the trail. The walls of the canyon rose around me. The small river crashing nearly 80 feet1 from the creekbed at the top of the fall to the rocks below muffled the nearby road. I stood and watched it, and even in the dark I could see the water flashing as it fell. I laid down in the gravel and listened for perhaps 20 minutes. There was nothing to hear but water.

It was still dark, but the sky sifted through the white pines rimming the canyon top was lightening up in the east. I studied a carpet of liverworts (Marchantia) on the cliff wall, pressing my face to it to see what I could make of the fleshy lobes in the predawn. The forest above had been obvious even in the dark: this subtler forest I only noticed as day started to break. As the sky grew lighter, chickadees started to move around, febeeing to one another. The days are growing longer.

I walked up and out. By the time I reached the ridgetop, it was light. The 15 minutes before sunrise go remarkably quickly, relaxing into dawn over the course of just a few minutes. I came across several trees that appeared to have been gnawed to pieces. One had rained wood chips, forming a halo on the forest floor at its base that glowed like a sun rising through the oak leaves. Another had been chewed nearly to the ground. I don’t believe this is porcupine activity, though perhaps, nor beaver (we were too high up, and I saw no true beaver trees). It is a mystery whose answer will likely be obvious one day when I least expect it to. We ate as a group, then hiked around Wildcat Falls, where there were Pennsylvania sedge and black oak with mossy rugs between, a krummholz-like copse of stunted oaks, white cedars on the edges of the ravines. We stood and watched Wildcat Falls filling the canyon with snowy ice shards. We passed white oaks spackled with Aleurodiscus and Auricularia, rhizomorphs of Armillaria. We admired the magnificent root system of a white pine that was exposed by erosion as it careened downhill toward the trail and trees whose wood had twisted as they grew, vessels intruding upon one another in systematic asymmetry: anatomy becoming morphology, morphology becoming forest structure, structure becoming the ways in which trees and forests shape the human environment.

Which is what we were at Starved Rock to talk about. So we hiked out, past a grove of rock polypody, the undersides of whose fronds were pocked with spores, and fallen black oak shoot tips, evergreen leaves of white avens, decomposing trees hosting gardens of bonnets or split open to reveal an unexpected grove of turkeytail fungi. Snow was on its way, and we returned to our meeting with the sense of efficiency that you get when weather is coming and everyone in the group wants to get home. We drove back to the Arboretum after lunch.

I biked home from the Arboretum just after sundown, as the snow was beginning, when you have that delightful feeling of the snow just a little icy, pricking your cheekbones as home pulls you in, and you know it’s warm there and your family is home and it will be supper time when you get there, and there’s tea and maybe a movie that night.

The next day was snowy, then temperatures dropped to the low teens, where they should be in January. It was now a month past the solstice. Someone I was reading last year–probably Burroughs–pointed out that the climatic height of the season lands about one month after the astronomical turning point: the hottest summer and the deepest winter are each about one month after their respective solstices. I had never thought of this, but our temperatures bear it out: the hottest day of the year in Chicago is July 18, not June 21; the coldest is January 29 instead of December 212. Monday afternoon, I watched a great blue heron fly off over the road just as I was riding out of the Arboretum. Wednesday afternoon, stepping out of the house with the dog at 4pm, I felt as though I were looking through a bank of ice. At Maple Grove Forest Preserve, the snow was pierced by Carex jamesii. There were gray squirrel excavations and an orange mycena mushroom desiccating on a log in the snow. American pokeweed was crumpled cross-legged in the thicket where it had grown in abundance late into fall. Armillaria rhizomorphs were everywhere: on red oaks, on sugar maples, everywhere that bark was stripping from a tree.


I read back over what I’ve written and say aloud to myself some of the words I’ve chosen (Armillaria, babbling, copses and creekbeds, dawn). I suspect that only humans worry about the words we choose. Only a human could drift so far from itself as to say, as N. Scott Momaday wrote, “… and always I listen to my writing. I must hear it or else I cannot appropriate it to my spirit.”3 Only a group of humans would get together in a place as beautiful as Starved Rock to talk about trees. Yet we do. In the bargain, we get to enjoy the hell out of the waterfalls. We get to recognize that the world is beautiful. Can the other animals do that? I doubt it. I think the exchange is worth it.

It rained today, and the chickadees were singing. It’s dark out now, the snow is eroding away. I understand we are supposed to have more snow tomorrow, but the temperatures are projected to waver around freezing, so I don’t know whether it will stick around. I hope so. I so enjoy these few months of winter.


  1. Great Lakes Waterfalls. url: http://gowaterfalling.com/waterfalls/starvedrock.shtml (accessed 2020-01-19).
  2. Average temperatures in Chicago; scroll down to see the plot across the year: https://weatherspark.com/y/14091/Average-Weather-in-Chicago-Illinois-United-States-Year-Round
  3. N. Scott Momaday. 2018. Preface to House Made of Dawn, originally published 1966, 50th Anniversary Edition issued by Harper Perennial Modern Classics, New York.

The ashes of Maple Grove

The solstice this year was cold enough for ice crystals in the soil and crevices of fallen trees, warm enough for crane flies on the wing. In the hollows where the cold air pools, the ground was frozen and brittle. On the warmer slopes, it was clayey, plastic. Fungal mycelia were bedded down with the earthworm castings. A chainsaw buzzed in the neighborhoods to the west of Maple Grove. The Burlington Northern Santa Fe rumbled along the tracks at the south edge of the Forest Preserve.

I have been walking in these woods almost weekly for the past three years, more irregularly for the seven years before that. Around 2007, two years before my family and I moved to Downers Grove, emerald ash borers arrived in DuPage County from their point of entry in 1990s southern Michigan (the data is an inference, not an observation, as they weren’t discovered there until 20021). I work at The Morton Arboretum, where great attention was paid to the arrival of this xylophilous east Asian beetle. It was clear by the time that it arrived that the loss of the ashes would be inexorable, and over the course of a year or two, The Arboretum took down almost all of the great ash trees in the East Woods. I remember advising a friend to do likewise with the few ashes he was considering treating for EAB on his own property. They are goners, I reasoned. Why protect what you can’t hope to save? My neighbor, who is also a friend, was gracious. He is an actuary, and I get the sense that he thinks about things similarly. Whether he agreed with me I don’t know, but we are still friends.

This day, the solstice, after bumping into the crane fly, I encountered an ash approximately 80 feet tall, still clothed in bark, but loosely. I could peel it back easily with my hands, like the margins of a robe or cracked sheathing off of electrical cable. The inner surface of the bark was frosted, the bole inside was slowly being emptied out by carpenter ants, sawdust filling the gap at the base, the surface pebbled with excavations and etched, intricately, with emerald ash-borer trails. The bark rattled upward for 20 feet from where I had loosened it. At the foot of the tree, the crown had rained branches, perhaps in a storm. One had impaled the forest floor like a loosed javelin. No one had been hurt. Lichens from the canopy had fallen 50 or 70 feet and were now understory lichens, just for awhile, until they would be overtaken by someone else colonizing the fallen branches. The history of lichen succession that was for decades proceeding in open air at the top of this tree stood at the beginning of a new chapter, when it would be overwritten by succession in the rich forest leaf litter.

This was a magnificent tree. I noted its location and started to walk again. Within 20 feet there was another dead standing ash, then another. I looked around. More than ever before, I was struck by the hulking ash boles shattered on the forest floor or standing with broken crowns, splintered branches dangling. In the northern half of Maple Grove Forest Preserve especially, it seems the lion’s share of the fallen trees are ashes. There are fallen sugar maples and red oaks and bur oaks as well, of course, for these are the dominants of the forest now. But roughly two out of every three trees I encountered on the ground this day was an ash, and almost all of them a foot and a half or more in diameter.

An entire partition of this forest has gone down in the course of a decade. When I first walked in Maple Grove Forest Preserve, there must have been some emerald ash borers in the forest, but I was ignorant of them. Since their quiet arrival in our quiet town, the beetles have been inscribing passageways under the bark, devouring the phloem that carries food down from the leaves, and scratching up the outer layers of xylem that carries water upward from the roots. It’s been a slow but invisible death2 under our noses, as the insects worked on the trees from the crown downward3. They arrived as adults, chewing on the leaves, and would have been apparent to the attentive as the upper branches died4. But as those rich upper leaves wilted and the trees were weakened, the beetles moved their way downward and choked the trees off at their trunks. The final death has been abrupt as it seemed: even if the insects were there for a decade, the trees gave up over the course of a couple years.

Ashes have been drawing in carbon and giving back for 1000s of years in these woods, and they are the sole food or breeding home for an estimated 43 invertebrate species and a nonexclusive source for an additional 2405. Green ash alone was, ten years ago, the fourth most important urban tree species in the Chicago region based on basal area, the eighth most important in terms of carbon sequestration, and the single most abundant street tree6. Loss of the ashes will profoundly affect the forests we walk through.

I have been watching these trees come down increasingly over the past three years. But it was really this fall that I became aware of the magnitude of the problem. In the past six months alone, numerous trees have fallen right over or beside the paths I walk most often.

But this day was the solstice, when “promise wakens in the sleeping land,”7 and I was more than usually aware that even dead, the ashes are not quite done giving. There are the ash seedlings that we find all over the woods: what their future is we don’t yet know, but it’s hard to imagine that it’s promising. But it’s not just the seedlings I look to today. The adults themselves have become knitted through with fungal hyphae, feeding woodpeckers in abundance as they desiccate in place and become riddled with new insect tunnels and their attendant bacteria, then shatter and fall to the ground. The carbon they’ve stored up will return to the forest in a slug, enriching the soil, forming bedding and fertilizer for wildflowers and new trees.

We are living through the third eradication by disease in roughly a century of an eastern North American tree: American chestnut, American elm, now the entire genus of ashes. It’s going fast, but it’s not over yet, and we won’t feel the last shocks for awhile. In the meantime, there is a lot of natural history wrapped up in death, decomposition, and the anticipation of what lies on the other side of the gap. We are being handed tragedy on a grand scale and obliged, at this point, to wring what insights we can out of it and make better decisions next time, so far as we are able. I am reminded of T.S. Eliot’s “Ash Wednesday:”

Because these wings are no longer wings to fly
But merely vans to beat the air
The air which is now thoroughly small and dry
Smaller and dryer than the will
Teach us to care and not to care
Teach us to sit still.8

We are now two weeks into the new year. It rained all through the night on Friday, turning to snow some time Saturday morning. St Joseph Creek was running high by the afternoon. The pond in the middle of the preserve was so high I didn’t recognize it at first, depositing ice five to 20 feet from its edge that would slump when the water beneath receded a few days later, and the upper surfaces of the leaves and branches were frosted with wet snow that, by the time I found it, was bristly with needles of ice. Everything looked cleanly hairy, like a scurfy enchanted lawn.

Walking around the edge of a wetland perched at the top of the hill near the south edge of the preserve, I passed an enormous red oak that was rotted out inside, cracked open at fifteen feet above the ground. It’s not just ashes that are going down, but for now, it’s mostly ashes. It will be for decades.


  1. Jonnes, Jill. 2015. Urban Forests: A Natural History of Trees and People in the American Cityscape, ch. 18. Viking, New York.
  2. Here I am indebted to Tricia Bethke, Forest Pest Outreach Coordinator at The Morton Arboretum, who graciously talked through some of the history and biology of emerald ash borer with me. Any errors are however mine.
  3. USDA Northern Research Station. 2016. Biology of the Emerald Ash Borer (web resource). url: https://www.nrs.fs.fed.us/disturbance/invasive_species/eab/biology_ecology/planipennis/ [accessed 2020-01-20; last updated 2016-03-14]
  4. Jonnes, Jill. 2015. Urban Forests: A Natural History of Trees and People in the American Cityscape, ch. 18. Viking, New York.
  5. Gandhi KJK, Herms DA. 2010. North American arthropods at risk due to widespread Fraxinus mortality caused by the Alien Emerald ash borer. Biological Invasions 12: 1839–1846.
  6. Nowak, David J.; Hoehn, Robert E. III; Bodine, Allison R.; Crane, Daniel E.; Dwyer, John F.; Bonnewell, Veta; Watson, Gary. 2013. Urban trees and forests of the Chicago region. Resour. Bull. NRS-84. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 106 p. https://doi.org/10.2737/NRS-RB-84.
  7. From “The Shortest Day” by Susan Cooper.
  8. T.S. Eliot, “Ash Wednesday.”

When we have compared everything in the world to everything else

We shall not cease from exploration / And the end of all our exploring / Will be to arrive where we started / And know the place for the first time — T.S. Eliot, “Little Gidding”

From late November through early December, I often feel as though the year has ground to a halt. We are waiting for the snows of midwinter. Leaves interbed in the rain, the loft of white oak and red oak and sugar maple leaves flattening, a few flowering plant seedlings twisting along over the soggy warmth of earthworm castings eroding to granules beneath the litter. The deciduous trees are done actively dropping leaves for the year: abscission layers have completed what work they will, cleaving off petioles and closing the scars before winter comes, shedding massive amounts of surface area before the biggest and most persistent snows, so the trees’ limbs are not torn off or dragged down by the weight of ice storms, arched downward for a week until it melts, cracking or shearing off where they have scarred in earlier years. Along a trail through the East Woods is a bur oak where just such a thing has happened in recent years, one of the enormous branching trunks sheared off where the join between the two was weakened, bark ingrown around a broken stem, the wood inside rotted, and when the branch fell a gallery of ant excavations was revealed, and sawdust spilled out to form a sprawling, shallow slope at the base of the tree.

Squirrels’ nests are exposed to view, and I find myself evaluating their handiwork as I walk through the woods, wondering whether the sloppier ones are truly the work of shifty males who have little to worry about if they should fall in a storm, and so risk nothing, as I must have read somewhere or perhaps was told by another naturalist; and to what degree the amount of time a squirrel spends on its nest has been optimized by natural selection. Have storms selected for more diligent squirrel populations on windswept hilltops? Have squirrels in the valleys grown rightly haphazard, throwing their efforts into food gathering in lieu of taking the extra time with hurricane ties? Surely someone has answered this question. It would only take tallying up the right kind of data. Isn’t that all any question takes, if it’s amenable to scientific inquiry?

The squirrels are quiet as I walk through, drowned out perhaps by the barking red-bellied woodpeckers. But it’s obvious what they’ve been up to. In a moss-lined crevice of a downed log between two trails, where no one would be likely to place one, there is a solitary blue cohosh berry, bright blue and undecomposed and still with a blush of wax. On a red oak log blanketed with seductive entodon moss lie the husk of an eviscerated black walnut and red oak acorn shells. They were left there by squirrels who spent a few minutes feasting where they could keep eye out, presumably, for predators.

The marcescent trees with leaves persisting through the winter are obvious now: often they are preferentially younger red oaks, to a lesser extent white oaks or older oaks. Beeches are festooned with white leaves curled like peppers. There is usually a residuum of leaves on the hop hornbeams and sugar maples. This year, we had heavy snow a few days before Halloween, and bitter cold, and my sense is that marcescence is higher this year than usual. On my walk home Friday afternoon it seemed there were more red oak shoot tips torn to the ground than I usually find. One that had tumbled onto the trail had larger and more pubescent end buds than we think of as typical for red oak, and I spent a bit of time worrying over whether it might be introgressed with black oak. Given the habitat and the lack of nearby black oaks, there’s no reason it should be. I suspect based on the work we’ve done in the past that this is just variability among individual trees: variability in marcescence, in strength, in domatia, the little patches of hairs that, in oaks, often lurk in the armpits of the veins on the undersides of the leaves, potentially home for mites and other invertebrates. When the leaves come down, you notice things.

Through the open woods, trucks can be seen rumbling down Finley past the power lines and prairie at the east edge of the Arboretum. There is a buck rub on a sugar maple. Stump puffballs have in some places exhausted themselves of spores. Elsewhere, fresh puffball bouquets erupt from cracked stumps, still white and feathery-fleshy inside. Oyster mushrooms are somehow still growing fleshy on the side of a fallen log. Chicken of the woods has bleached from its brilliant orange of late summer and early fall to a nearly pure white. The corpses of other mushrooms that I do not know are crumbling along the edges of the trail.


Saturday morning, the dog and I walk into Maple Grove Forest Preserve from the neighborhoods to the east. Nuthatches and jays are calling. It’s mostly been above freezing since Thanksgiving, but temperatures Friday night dropped to about 27°F. The ephemeral pond below the Avery Coonley School has grown a skin of ice. Frost crystals are three-quarters of an inch long under brittle heaved clods wherever the soil is exposed; anywhere there is at least a leaf or two lying over the top, the soil beneath is clammy and pliable. It takes so little leaf tissue to insulate the forest floor. It’s staggering in light of this to consider how much effect earthworms must have in just digesting leaf litter and exposing the soil to frost. Introduce earthworms, and even if they didn’t churn the soil and move nutrients around, their mere removal of insulating leaves would change the forest understory dramatically.

The Carex davisii foliage along the trail leading in is green and strong in spite of the frost. More delicate leaves are rendered pulpy by the ice. Admittedly, the evergreen winter sedges are low enough to stay under the snowpack; but when there is no snow, as now, how do they avoid being destroyed by the cold?

Near the entrance to the forest preserve, an ash about a foot and a half in diameter has broken off about 18 feet above the ground. The crown is leaning against a sugar maple 30 feet away, and the bark all the way up is flecked with turkey tail and other white rot fungi I don’t know but recognize from the other ashes that have fallen over the past few years. The wood inside is bleached. Further on, an ash of perhaps two feet in diameter lies across the trail. It rained broken branches as big around as a grown person’s thigh when it crashed down and caused havoc for fifty feet downtrail. Brooklyn jumps right up onto it and stands looking around. There are emerald ash borer carvings on the surface of the bole where the bark has peeled off. That’s two more ashes down in one visit. There aren’t many left.

Further on there is skunk fur but no carcass. The red oaks show perhaps less marcescence here than in the Arboretum’s East Woods, but there are still red oak shoot tips fallen. I again wonder if these fallen shoot tips are more common this year than last because of the early snow, breaking the branches before leaf fall. It would take counting fallen oak shoot tips year after year to know for sure, and then we would know. Wouldn’t we? There is no end of things to count in the world… we will never be done. I think this thought that has probably been thought in some form or other millions of times before, then I think of lines from Billy Collins’ “The Trouble with Poetry”:

And how will it ever end?
unless the day finally arrives
when we have compared everything in the world
to everything else in the world,

and there is nothing left to do
but quietly close our notebooks
and sit with our hands folded on our desks.

Observing and answering questions and analogizing never end. There will never not be something to count, never be nothing to figure out or see more clearly. Questions lead to questions.

Poetry fills me with joy
and I rise like a feather in the wind.
Poetry fills me with sorrow
and I sink like a chain flung from a bridge.

But mostly poetry fills me
with the urge to write poetry

On the walk out, I dig in the soil for false mermaid seedlings while the dog waits with uncharacteristic patience. Nothing. There’s another mystery: why can I never find false mermaid seedlings, our great winter annual, in the places where it will carpet the forest floor just four months from now? We shall not cease from exploration. There is no end of things to count and try to figure out.

Pacing the transition to winter

The leaves started turning color in earnest right around the 20th of October this year, then they sprinted through. By Friday the 25th the colors were near their peak, and incessant rain that Saturday afternoon through the night knocked much of the maple canopy foliage to the ground. Maple Grove was filled with people that Sunday. The floor was carpeted yellow and orange, with Carex jamesii sticking its mop-tops up through the fallen leaves. Moonseed leaves were blue-green, wild ginger was frozen at mid-senescence, leaves with a light yellow margin. An entoloma mushroom had been kicked loose and lay stipe-upward. Maple leaves were lodged in the splintering xylem of a decapitated ash. Dark green leaves of black cherry seedlings were more common than I had noticed previously. A single zigzag goldenrod still bore yellow flowers in the leaf axils.

We had snow that last week of October, Tuesday night on and off through Thursday. On my walk in through the Arboretum’s East Woods on the first of November, about half of the leaves were still in the branches, and the trees were tithing onto the fresh snow. The bright yellow maple leaves stood sharp against the sky as the sun was rising, and ones that had fallen were glowing against the snow like the wind-exposed edge of a smoldering oak log. Squirrels had been excavating the trails haphazardly. Their marks were everywhere. A dozen geese flew low overhead toward the west. A twelve-inch diameter red oak had tipped in the few weeks since I had walked the northwest end of the woodland trail. Was the snow so heavy that it dragged it down, full of leaves? Following the trunk to its roots, I flushed a woodcock from the ditch where it had been standing. The bird hummed through the woods at half-sapling height and settled down out of sight. Woodcocks follow the worms northward in the spring; I imagine they follow them back southward in the fall, and there were certainly active worms beneath the snow and leaf litter that morning. Juncos buzzed around in the shrubs. Robins flocked in the treetops.

By the weekend the snow had melted. Before doing so, it managed to knock more than half of the leaves to the ground, and the yellow sugar maple leaves on the snow had settled to the soil’s surface. The ground was a mottled yellow carpet that rolled beneath the trees and sloped down to ravines that I haven’t noticed since the wildflowers started to catch our eyes in March. That’s eight months of treating the landscape as just a substrate for beauty, soil and leaf litter as canvas and gesso. Now, who has the last word? The skeletons of jewelweed were knocked to the ground. The wood nettle leaves, frozen, hung like rags.

It’s the middle of November now and we have had snow again for a week. It is eroding irregularly. In much of Maple Grove, there are patches of snow only, white against the quiltwork of leaves being wearied into the soil by the frost and damp. Snow piles on shelves of turkeytail fungus and secludes itself in the bark-fissures of fallen logs. Along the long north-facing slope climbing up from the main section of the Forest Preserve, it coats the forest floor more evenly, displaying the leaves of the trees standing above it. One area is a pond of sugar maple leaves that three weeks ago were bright yellow and fleshy on our late October snow, but are now turning ochre, dry but not yet desiccated, curling upward at the edges. Another portion of the woods is peppered with flat, leathery red oak leaves. Beside a colony of Carex jamesii, someone has scraped the snow away in an area nearly the size of a piano bench. There are no footprints, and it does not look like a person’s work. Are squirrels collaborating these days? The snow is just damp enough to capture squirrel prints in near-perfect relief. It is not the thin skid of snow particles that capture every claw and pad detail, but that may be blown away by the first big wind, but the wet casting snow, the snow that hangs onto prints in enough detail for you to learn from them and ask questions. The squirrel stopped here for a moment: was it sitting up straight? Was this one running for food, or running from a coyote? The snow records and conceals by turns.

Yesterday afternoon1 was sunny and warm, between the high 30s and low 40s. The evening before, about 5 p.m., the dog and I had watched a great horned owl calling from the canopy tree stripped clean of its leaves at the north edge of the forest preserve, behind the houses. He was perhaps 30′ up, but with the leaves gone, I could see him lean forward as he called, stretching his body into what I imagine is a near-optimal configuration for maximal volume and pitch. Animals are clever that way. Friday afternoon, a flock of perhaps 100 sandhill cranes had flown southward over our house. Now, as we walked in about an hour before sunset, there were white-breasted nuthatches and hairy woodpeckers, squirrels and red-bellied woodpeckers barking. Elmleaf and zigzag goldenrod and calico aster are holding onto their achenes. White snakeroot has dropped its fruits, and the phyllaries remaining are recoiled and twisted like the arms of starfish in slow movement. Dehisced halves of willow herb capsules were twisted alongside the skeletons of bur marigold, whose seedheads were mostly shattered. Basal leaves of black snakeroot and cauline leaves of blackberry were still green, and of course so were the Eurasian honeysuckle.

At about 4:30, a pair of great horned owls started calling back and forth to each other. Brooklyn got particularly agitated, and we accelerated around the loop toward home. Two black squirrels chased up nearby tree trunks. They were smaller than I remember, and I wondered whether they were this year’s young. As we came down the north-facing slope toward the trail out, the snow and the scattering of red oak and sugar maple leaves made it feel like Thanksgiving time in upstate New York. In the distance, a siren was singing, and alongside it I thought there might be coyotes. Brooklyn and I listened, but neither of us was certain.

I have read sections of Sean Borodale’s beautiful Bee Journal over and over this past month. I’d like to share a dozen of his poems with you, but I’ll leave you with this one, “3rd December: Notes”:

Listen to the rain, the rain, the rain, like the wings and legs of bees walking across bees, like the lyre of a thought, a whole possible instrument of insects.
Listen to the rain, more rain, treadling earth to the sodden cold wet spun heads of this room, pacing the winter to and fro…

We are pacing back and forth into winter ourselves this year. We do it every year, and every year looks different.


1 16 Nov 2019


Plants referenced:

[photos linked here]

  • Carex jamesii – James’s sedge
  • Acer saccharum – sugar maple
  • Menispermum canadense – moonseed
  • Asarum canadense – wild ginger
  • Prunus serotina – black cherry
  • Solidago flexicaulis – zigzag goldenrod
  • Solidago ulmifolia – elm-leaf goldenrod
  • Laportea canadensis – wood nettle
  • Symphyotrichum lateriflorum – calico aster
  • Epilobium coloratum – willow-herb
  • Ageratina altissima – white snakeroot
  • Sanicula odorata – black snakeroot
  • Quercus rubra – red oak

A hesitant turn toward fall

The woods appear to be tumbling into fall unwillingly over the past month. The first week of October, I spoke to a radio journalist who asked me why fall color was coming so early. I said I didn’t know, referred him to Christy Rollinson and Ed Hedborn because they could speak to the matter with data. But what struck me was not how early the woodlands were turning toward fall, but how reluctantly. The maples were mostly browning, scraps of yellow flesh spreading from the spots and crisped margins. Variegated and tattered false Solomon’s seal reclined against fallen logs. Squarrose sedge infructescences were dark, papery. They went to pieces at a touch. I shook a spike’s worth of perigynia in my fist, and they rattled like the exoskeletons of dead beetles. There was a hole in a fallen tree the diameter of a #2 pencil, flanked by lichens and mosses and a centipede. How many lives have revolved around that opening? How many mites and bacteria have been born, reproduced and died within inches of this hole? Manyfold more individuals than I have ever known by name.

By the end of the first week of October, an east-facing slope in the East Woods that had been green with false mermaid and Dutchman’s breeches in the spring was bare, about 80% dirt and last year’s old leaves, some burned out maple saplings, leaves of swamp buttercup and carrion flower. The trail leading south out of the Spruce Plot, which passed through waves of pale jewelweed until mid September, was flanked by skeletons, most fallen, leaving pallid stalks on the ground interspersed with wild ginger and moonseed leaves that were hidden beneath the jewelweed hummocks. Enchanter’s nightshade leaves were all fallen, leaving bristly flowering stalks. Evergreen, almost blue-green hepatica bouquets were nestled beside fallen logs and the bases of trees. They’ve already laid by what they need to get through winter and are ready for the snow. Rotted black walnut husks littered the ravines below hills where the adults were shedding their leaves. A few giant puffballs were still swelling on the slopes. Bluebirds warbled around. Whitegrass was the color of lime sherbet. A colony of false rue anemone two feet across was sending up new leaves in the shelter of a sugar maple.

We’re three weeks into October now, and the colors are finally starting to turn in earnest. White pine needles are yellowing. The crown leaves of bur oak and black oak are falling, exposing the odd squirrel nest. Juncos have come back into town and are rattling from the shrubs, while the golden-crowned kinglets lisp their way around the forest midstory. Robb Telfer reports that woodcocks visited Ware Field the night of October 17. Crickets purr all day long, no longer content to sing by night and early morning. Moonseed leaves are curled into saucers. Stinkhorns are glossy and swarming with gnats and flies. A dryad’s saddle I have watched erupt from the same side of the same tree the past two years has withered and broken off and is curled in fetal position at the base of the trunk. It will fruit again next year. Pores have started opening in the crowns of the stump puffballs, which are yellowing inside or already gooey in the middle and gone to spore around the edges. Horse-gentian berries are bright orange and filled with blackish achenes. Long-bristled smartweed along the trails is the brightest flower in most of the woods, an émigré from east Asia, as delicate as baby’s breath. White snakeroot fruits are as prickly as hoarfrost. Black walnut husks are disintegrating, exposing the rugged nutshells. A few shagbark hickory nuts remain to be cached or eaten. The last fruits are hanging onto the stem: carrion flower berries, cottony thimbleweed fruits, zigzag goldenrod and elm-leaf goldenrod, woodland tick-trefoil, white baneberries rotting on the stalk. Bottlebrush grass seeds are almost all fallen from the stalk, and the stems are reclining. Largeflower bellwort foliage is pale yellow. Alder buckthorn berries are ripening. Virginia waterleaf looks as fresh as it did at the end of June.

Fall is far from over, and the lawns have had a renewed life in the last weeks before the frost. The grass is bright green. Chicory and red clover are blooming. Rosettes of mullein leaves as big as serving platters are splayed out along the edges of the roads. Painted ladies are hopscotching over the gardens. Feathery fruits of asters and goldenrods waft along beside me as I walk. Mushrooms are drying in mulched beds. Fruits are ripening on hackberries planted in the parks.

Saturday afternoon, my older son and I took a short walk in the East Woods. We found aborted entoloma on a rotting log. Carex radiata was still putting up shoots within a ring of fallen culms. There were white oak acorns germinating in the middle of the newly raked trail and a red oak seedling.

The maple leaves are finally yellowing. It may not be a fall like last year’s, but it will do just fine. There is far more to look at than fall color.


Plants referenced

  • Acer saccharum – sugar maple
  • Actaea pachypoda – white baneberry
  • Ageratina altissima – white snakeroot
  • Anemone virginiana – tall thimbleweed
  • Asarum canadense – wild ginger
  • Carex radiata – bracted sedge
  • Carex squarrosa – squarrose sedge
  • Carya ovata – shagbark hickory
  • Celtis occidentalis – common hackberry
  • Circaea canadensis – broadleaf enchanter’s nightshade
  • Desmodium glutinosum – woodland tick-trefoil
  • Elymus hystrix – bottlebrush grass
  • Enemion biternatum – false rue anemone
  • Frangula alnus – alder buckthorn
  • Hepatica acutiloba – hepatica
  • Hydrophyllum virginianum – Virginia waterleaf
  • Impatiens pallida – Pale jewelweed
  • Juglans nigra – eastern black walnut
  • Leersia virginica – whitegrass
  • Menispermum canadense – moonseed
  • Persicaria longiseta – low smartweed
  • Pinus strobus – eastern white pine
  • Quercus alba – white oak
  • Quercus macrocarpa – bur oak
  • Quercus rubra – northern red oak
  • Quercus velutina – black oak
  • Ranunculus hispidus – swamp buttercup
  • Smilax sp. – carrion flower
  • Solidago flexicaulis – zigzag goldenrod
  • Solidago ulmifolia – elm-leaf goldenrod
  • Triosteum perfoliatum – Perfoliate Tinker’s-weed, horse-gentian
  • Uvularia grandiflora – largeflower bellwort
  • Verbascum thapsus – great mullein

Spring peepers, fall peepers

Spring peepers were calling this week in The Morton Arboretum’s East Woods, and false rue anemone foliage has re-emerged there and in Maple Grove.

Monday morning, fog was pooled in the prairies beneath the power lines and draped between the spruces. There was a dusting of mosquitoes. Crickets were purring. The creeks and ditches were filled with water. Along the chipped trails angling up the moraine northwest from the Big Rock Visitor Station, stump puffballs continued to ripen, syrupy brown like piles of gulab jamun, smooth, the insides still white, mostly, but going to spore. Tiny puffballs had started to emerge in separate patches. Earthstars had erupted from the mulch throughout the East Woods. Stinkhorns were emerging and swarming with gnats and relentless carrion beetles. The young ones looked like brussels sprouts pushing up from the wood chips. The older ones had already fallen.

Spring peepers were singing all day Monday. I have heard chorus frogs and, I’ve suspected, the odd spring peeper in past autumns, but Monday it was peepers in every tree. The squeaks, trills and whistles were unmistakable, but shifted upslope and displaced in time by about 6 months. There were so many of them, I could not convince myself at first that they were really peepers, especially at this time when songbirds are migrating through. I stood still and watched, but I saw nothing. I waded into the sunflowers and towering wild lettuce to flush out any birds, but the calls only stopped, as frogs always do when you go hunting for them. Peeps punctuated the woods west of Big Rock Visitor Station all the way down to the service road that bisects the Heritage Trail and runs north through the meadow. I was surrounded by them, and there was nothing they could be but peepers. Nonetheless, only after chewing on it all day and walking out the same direction, then hearing them again on my walk home about 4:30, was I certain that these isolated cheeps and whistles were what they sounded like.1 We see what we expect to see, and we interpret data in light of things we’ve come to believe.2 They might sound like peepers, we tell ourselves, but it’s fall migration. They must be birds. To hell with evidence.

When I arrived Wednesday morning I had about 30 minutes to spare. I made a quick stop to listen for them again. There was a new crop of little stump puffballs coming up and tufts of Hemimycena in the chipped trails, a few grapefruit-sized white puffballs in the understory. These may be young giant puffballs, but I doubt it: I would expect them to be much larger, so they might be any of a number of species. I passed a false Solomon’s seal tipped with a raceme full of ripe berries in perfect condition, good enough to eat. When I got back to the same site where I had heard the peepers on Monday, there was no sound. Temperatures were about 20 degrees cooler than when I had been there on Monday afternoon. Gnats were still buzzing around the stinkhorns, but they were fewer and less frenetic. Then, from a hollow tucked in between the shortcut trail to Big Rock and the trail that runs west along the ridge of the moraine, a single peeper called. I walked down into the hollow and poked around for five or ten minutes, but there were no other calls.

It turns out, however, that the next 36 hours were filled with songs as unexpected as the spring peepers’. On my drive home, Coltrane’s solo on “Giant Steps” came over the radio, piercing the seams between measures as though there were no chord changes, as though the bricks etched across the staff had dissolved together. The next morning, as I biked toward the Roosevelt stop to catch a train to the university, a street musician playing vibraphone on the corner of Wacker and Jackson pounded descent with modification momentarily out of my mind. Then, after working all morning on a lecture, I came across campus toward Cobb Gate and heard the unmistakable sound of a pipe organ. Surely this was my mind playing tricks, wishful thinking. I was hearing construction noise, or a truck rumbling down the street. But no: subwoofers parked along the sides of the archway between the library and campus were pumping out pipe organ music, bird songs, low rumblings you could feel in your knees.3 You hear what you expect to hear.


I’m writing this on Friday, which I’ve taken off for my birthday, after visiting Maple Grove. The maple leaves have turned yellow in the past week and started falling, the lower branches of the elderberry corymbs have started breaking, the ray flowers have fallen from the wingstem, the zig-zag goldenrod heads are turning pale and filling with feathery achenes. The woods are filled with lisping sparrows. Wood nettle leaves are chewed to lace, but there is enough sting left in them to catch at least this botanist off guard. Pale jewelweed is provisioning its late-season capsules. The galls blistering along its leaf midveins are darkening along one side. I suspect that the gall midges inside are nearing maturity. I didn’t break any open today, out of a sense of compunction that I rarely feel regarding the welfare of gall-making insects. Wild leek has dropped about a third of its seeds. Cystopteris fronds are crumbling, fowl mannagrass culms are reclining, enchanter’s nightshade leaves seem to have all fallen, leaving the stalks bristling with fruits. False rue anemone is sprouting anew, however, and there is an ankle-high clump at the base of a maple near the entrance to the woods. Christy Rollinson found the same thing in her phenology survey a week ago in the Arboretum’s East Woods. I found a few young shoots in December of last year as well. Is fall re-emergence of false rue anemone the new normal? Or have we simply been failing to notice it in past years, because we weren’t expecting spring plants to emerge in the fall? You sometimes don’t see what you don’t expect to see.

Carex jamesii clumps stand out like sentinels in the understory, bright and alert while the trees and most of the forest herbs are trundling off to bed. They will remain green and active under the snow all winter long. I visited a clone of Carex woodii twenty feet across that I run across every few weeks, and I was impressed at how it seems to exclude almost all other species. There are a few thigh-high ash saplings, a solitary and well browsed burning bush, a handful of Virginia waterleaf and zig-zag goldenrod, but little else. Is this competitive exclusion, or is the sedge just growing in an opening in the sugar maples where nobody else wants to grow? Distinguishing cause and effect from common cause and plain old dumb luck is the bane of most observational studies, with the exception of phylogenetics, the observational science that insists on reconstructing history.

Tall beggarticks is shedding sharp-tipped achenes that stick in your socks and sweaters. Jack-in-the-pulpit is reluctantly letting go of the last of its berries. Late figwort capsules are mostly broken open. Crown-tipped coral fungus has been out months, and today I found a sprawling coral fungus that looks different, white coral fungus perhaps. Handsome clubs have emerged from under the leaf litter. Honey mushrooms are growing not far from where I’ve been finding one of their messier relationships, the aborted entoloma, for the past few weeks. A nearly-dead sugar maple near the bridge across St. Joseph Creek is sprouting shelves of late fall polypore, Ischnoderma resinosum, a saprophyte, though the tree has one branch growing about 20 feet up toward the north. It appears to have been topped sometime in the last decade or so, and the top to have fallen off to the south side of the bridge, where it lies decomposing on the slope just up from the creek. Deeper in the woods, what I take to be the same fungus is growing on a dead standing ash. Stump puffballs are emerging from the mulch forming inside a rotten stump of another fallen ash, where the brown rot is wettest and least recognizable as wood.

As I was leaving, I passed a brown-rotted log and broke into it to see what was going on inside. A bald-faced hornet hid in a hole right at the edge of the piece I broke off. Was she preparing to overwinter? From what I have read, this is the time when bald-faced hornet queens should be settling in to wait out the cold. She was not aggressive, did not defend herself, barely righted herself when she fell over. Her abdomen was pumping, voluntarily or not, and I wondered whether this was an ovipositing movement. I wondered whether she was a queen at all, a worker chewing on wood too late in the season to make a nest of it, or someone else altogether.

Further on, a melanistic gray squirrel scampered away from me and up a tree. But no toads or frogs singing. During the day, I found out that Christy Rollinson found spring peepers in her seed traps in the East Woods, and Meghan Midgley reports that they’ve been showing up in her nitrogen deposition collectors. I can’t help thinking this is an odd fall, but every season is odd in some way. Maybe in another 50 years I’ll know what normal is.


References

1 For a nice description of late-fall peepers and the bafflement they can cause naturalists, see Caduto, Michael J. 2016-09-16. Fall peepers. Northern Woodlands. url: https://northernwoodlands.org/outside_story/article/fall-peepers [accessed 2019-10-01].
2 For an extended and nuanced consideration of the implications of confirmation bias, see Powers, Richard. 2018. The Overstory. W.W. Norton & Company. Along the way, you’ll find an extended and nuanced consideration of a lot of other things in there as well.
3 David Wallace Haskins, Breath, 2019. You can read more on this exhibit and the other exhibits associated with The Chicago Sound Show, at the website of the SMART Museum.


Plants referenced:

  • Acer saccharum – sugar maple
  • Allium tricoccum – wild leek
  • Arisaema triphyllum – Jack-in-the-pulpit
  • Bidens vulgata – tall beggarticks
  • Carex jamesii – James’ sedge
  • Carex woodii – pretty sedge
  • Circaea lutetiana – enchanter’s nightshade
  • Enemion biternatum – false rue anemone
  • Fraxinus alba – white ash
  • Glyceria striata – fowl mannagrass
  • Hydrophyllum virginianum – Virginia waterleaf
  • Impatiens pallida – pale jewelweed
  • Laportea canadensis – wood nettle
  • Maianthemum racemosum – false Solomon’s seal
  • Sambucus canadensis – elderberry
  • Scrophularia marilandica – late figwort
  • Solidago flexicaulis – zig-zag goldenrod

A conviviality of being

In deep time, species come and go. For now, though, I wish I could go back and botanize this forest for a season or two with ashes still in it.

Friday night the rain pummeled the forests. It appears to have blown some birds into town: the parking lot by Mays Lake was lisping with sparrows when I arrived with the dog at around 6:30 the next morning, and song sparrows were singing. On my way out the driveway, a bird flew off from the middle of the road that looked for all the world like a woodcock. I didn’t get a second look, however, and I am not certain. The rain knocked down acorns by the bushel. Disembodied red oak acorn caps are washed into the parking lot corners. False trails appeared in the woods overnight where the rain had washed the leaf litter clear and left the detritus of early autumn along the margins, twigs tangled up together and stretched downslope. Autumn was already getting a start. Shagbark hickories were falling ripe this week, and black walnuts had begun blackening beneath the trees, lolling over on their sides and caved in where the husks have started to decompose. Buckeyes are cracking open, husks rolling off, nuts coming to rest unnervingly reminiscent of eyeballs that have been kicked off to the sides of the trails. White oak acorns have been falling fat and furious and germinating on the ground: root tips are tucked in along the stylar ends of the nuts or facing straight out, endeavoring to pierce the leaf litter and get a toe-hold before the desiccating winds of winter. Every tree knows fall is coming. Friday’s storm sealed the deal.

I spent a couple hours Saturday morning in Maple Grove Forest Preserve. St. Joseph Creek was about a foot higher than usual and murky. The ephemeral ponds were all recharged, ankle-deep. The American pokeweed is majestic, dripping with racemes of plum-colored berries, towering over the dilapidated jewelweed–they barely made it to fall–like the oldest white pines in the northwoods piercing the maple canopy surrounding them. Leaves are yellowing: poison ivy, wood nettle, choke cherry, ash, Virginia creeper, basswood, American elm, large-flowered bellwort, black snakeroot and white grass. One maple that has fallen across the creek is showing the oranges and reds of October, but barely.

Jumpseed and stickseed (Hackelia) fruits are blackening. Blue cohosh foliage has fallen, abandoning the naked seeds to whatever birds and mammals will take them. They are unnervingly blue, floating among the shrubs. Doll’s eye berries are hanging on, and their parents appear still to be laying up treasure on earth, provisioning the rhizomes for next year, not giving up on their leaves yet. Why? Here are two herbs that seem so alike in habit and behavior in midsummer. Perhaps we need to look to early spring. The blue cohosh I noticed as early as April 11 this year, about to bloom two weeks later. White baneberry I noticed in flower only in mid-May. Perhaps each chooses its risk: blue cohosh bets against late spring snow, white baneberry against early frost. Wingstem fruits are clinging in tight little heads. The blue asters (Symphyotrichum shortii, Symphyotrichum drummondii), calico aster, and zig-zag goldenrod are all in full bloom. Flowers are still hanging onto the white rattlesnakeroot. A stand of phlox persists near the top of the hill.

I walked through the shin-high sugar maple seedling grove tucked between the creek and the houses at the northwest edge of the preserve. There is very little there, though a colony of perhaps 300 to 500 wild leek scapes in full fruit captured my attention for several minutes. A fallen tree that I suspect based on its stature and landscape position is a sugar maple lies rotting like a canoe filled with decomposing sawdust. The outer layers of wood are still intact, curled around a moist and granular humus. Why have the outer layers persisted while the inside has rotted? Nearby is a downed tree that I take to be a red oak, but it has done the opposite: the outside is rotted away, leaving the bole a brown-rotted, intact core that looks as though it would go to pieces if you kicked it, which I do not. It is riddled with holes and architectural in its beauty, blocks of xylem angular and displaying the attributes of wood that we look for in anatomy class, cradling pockets of chipped wood actively being worked over by earthworms. In an otherwise magnificent woods, this lawn of maple seedlings strikes me as relatively sterile, but even here there is a lot going on.

The sheer number of dead ashes and their immensity hit me as I walked Saturday. I notice the dead ashes in these woods every time I walk: the network of ridges in the bark of the lower bole and, especially at this season, the densely packed fungi on the trunk–turkey-tail, chicken of the woods–grab my eye as I am walking by. Often there is a gap in the woods where the snag still stands, and trees or shrubs or tall late-summer herbs grow thicker. What struck me on Saturday was the fact that these ashes that have mostly all died within the past decade were as big around as the red oaks and sugar maples that dominate the forest… and there were many of them. Emerald ash borer appeared in DuPage County in around 2007. That’s just twelve years ago. There are still little ashes sprouting in the woods, but I have not seeing a single living large ash in these woods. Every one is still a home to insects and fungi, feeding the woods for now. But within a generation they will be as gone to us as the American chestnut.

I walked out past the white oaks and bur oaks at the top of the hill by the parking lot at the south end of the preserve, each shedding acorns, doing well, standing in for the ashes, filling in for them as best they can, but not really. No species can stand in for another. I passed a row of trooping crumble caps on a fallen log that glistened in the rain like porcelain. Somehow I started thinking about the contingency of evolutionary descent, radiation, and adaptation, how you get only what you get, and only once. Pull one thing out, and all the other species will fill in as best they can. Fifty million years hence, whoever is here will miss the ashes in the way that we miss the tree-sized horsetails and lycopods, the velociraptors. They will have their world, one that comes from ours but has a very different shape. “When viewed in deep time,” Robert Macfarlane writes, “things come alive that seemed inert. New responsibilities declare themselves. A conviviality of being leaps to mind and eye. The world becomes eerily various and vibrant again.” 1

In deep time, species come and go. For now, though, I wish I could go back and botanize this forest for a season or two with ashes still in it. Somehow I’ve already forgotten what it was like, and it’s only been ten years.


References

1 Macfarlane, Robert. 2019. Underland: A Deep Time Journey, p. 16. W.W. Norton & Co., New York.


Plants referenced

  • Acer saccharum – sugar maple
  • Actaea pachypoda – doll’s eye, white baneberry
  • Allium tricoccum – wild leek
  • Carya ovata – shagbark hickory
  • Caulophyllum thalictroides – blue cohosh
  • Fraxinus sp. – ash
  • Hackelia virginiana – stickseed
  • Impatiens capensis – jewelweed
  • Juglans nigra – black walnut
  • Laportea canadensis – wood nettle
  • Leersia virginica – white grass
  • Nabalus albus – white rattlesnakeroot
  • Parthenocissus quinquefolia – Virginia creeper
  • Persicaria virginiana – jumpseed
  • Phlox sp. – phlox (I believe this one is a garden phlox)
  • Phytolacca americana – American pokeweed
  • Prunus virginiana – choke cherry
  • Quercus alba – white oak
  • Quercus macrocarpa – bur oak
  • Quercus rubra – red oak
  • Sanicula odorata – black snakeroot
  • Solidago flexicaulis – zig-zag goldenrod
  • Symphyotrichum drummondii – Drummond’s aster
  • Symphyotrichum lateriflorum – calico aster
  • Symphyotrichum shortii – Short’s aster
  • Tilia americana – basswood
  • Toxicodendron radicans – poison ivy
  • Ulmus americana – American elm
  • Uvularia grandiflora – large-flowered bellwort
  • Verbesina alternifolia – wingstem

If you are a human collecting acorns

If you are a human collecting acorns, the deck is stacked against you. Every creature in the woods wants them, and most balanophiles are more nimble than we. In North America, we often think of squirrels as our primary competitors, and they are of course efficient: acorns scarcely drop before they are scavenged and cached, and many are collected straight from the trees. The chipmunks I suspect are nearly as efficient, if smaller. But there are also jays, turkeys, rabbits, raccoons, opossum, deer, mice and voles, a host of others. This diversity of acorn-eaters shouldn’t be surprising. Acorns are tannin-rich, which is a barrier to ingestion, but they are energy-rich as well, almost 90% carbohydrates by weight1. Humans have as far as I know no adaptations for dealing with the tannins in the acorns, but even we can eat them with a modicum of processing1. Hominins have been in fact been processing and eating acorns since at least the mid-Pleistocene2, roughly 600,000 years ago before the origin of modern humans. Imagine how much more we’d eat them if we were out there all the time, living among the trees, keeping track of this particular mother oak, and that one over there that did so well the previous year.

This past week, two of my colleagues and I collected acorns from bur oaks in several DuPage County forests for an experiment we are planning. We found that we were about one week later than we ought to have been, which I had feared we would be. On Monday of the previous week, I had been seeing the first good bur oak acorns drop. Prior plans got in the way of collecting: the next day I was on a Cessna 8-seater over Buzzard’s Bay, heading to Polly Hill Arboretum to speak about the 56-million year history of oak evolution, knowing full well that the acorns were dropping in earnest back home. By the time I could get out again a week later, the best bur oaks had already been pillaged: the fullest fresh acorn caps were empty, and almost every nut from the present year was about a nickel in girth. Fresh caps as big around as 50-cent pieces lay on the ground, every last one of them stripped of its seed. Moreover, there were many fewer good acorns to begin with than there had been in 2018, when I easily found good acorns in abundance under many of the oaks in each population I visited. The largest difficulty had been identifying trees that were sufficiently separated from each other that I could tell who the mother was for each acorn. This year, I found scores of oaks with only one or two acorns beneath them, but 100s of the previous year’s acorn caps.

But it’s not just the squirrels and chipmunks you have to watch out for, and perhaps not even primarily. Anyone who has collected acorns has at least once brought home a bag of them only to find the bag crawling the next morning with larvae. This year, many of the acorns we collected had tiny orange wrigglers underneath the caps. Those seemed to be fine: we could wipe the larvae away, and I was grateful we caught them before they could do more damage. But at one site, every second or third acorn had a black scar at the base, cracking open the acorn cap and the wall of the nut. These we discarded. At others, almost every acorn was sodden and easily crushed in my hand, filled with frass, presumably from weevils. Many had a hole in the side where an insect had chewed its way out. It is remarkable to think how many acorns must be produced in a good year that we humans would never have a chance to get our hands on. We couldn’t possibly be quick enough.

*

Saturday afternoon, Maple Grove Forest Preserve was glazed with rainwater. It was coming down episodically, but St. Joseph Creek wasn’t high yet. The creek is very flashy, and with a little downburst it swells, and with a little more it’s eager to overspill its banks. Wild leek seeds are mostly exposed now, pearly black inside the torn white sheaths. Doll’s eye berries are still bright white and clinging to the inflorescence axis. They seem to me to be ripe. Are they waiting for something? Are they really not ripe yet? Or do they perhaps just not taste as good as the other berries, so don’t get eaten as readily? Perhaps their elevation on tall talks makes them inconvenient for mice, voles, raccoons who might otherwise abscond with them. By contrast, Jack-in-the-pulpit berries at shin height are essentially gone. So are the false Solomon’s seal berries. Black snakeroot burs seem finally to be falling of their own volition. I’ve been impatiently breaking them up and scattering them as I walk by for the past month, but now they appear to be shattering on their own, or getting dragged around by passing mammals, presumably not all of them botanists. Jumpseed in the deepest parts of the woods have been biding their time for weeks, still putting resources into their seeds, but now when I touch them the reflexed fruits spring off into the surrounding foliage. I wonder why I don’t see whole gardens of seedlings beneath each plant in the spring? It may be that the seeds are tasty and get moved around by rodents or insects. It may be that they have low viability. Or it may be that I just haven’t been noticing the seedlings. I’ll keep an eye out in the spring.

Ghost pipes are ripening, turning their faces to the sky. Aborted entoloma, which I started noticing a week ago, has appeared everywhere now, like loaves of gnome bread leavening in the leaf litter. It extends at least from near the backyards at the northwest corner of the forest to the north-facing slope leading down from the picnic area by the parking lot at the south end. From what I’ve read (see last week’s post for references), the presence of the aborted entoloma makes me think that honey mushroom mycelia, Armillaria mellea, are everywhere as well. Stump puffballs are starting to go to spore: some are brown and dry inside, others are still white but granular. Earth stars have appeared along the trails. There is a patch of chicken of the woods on a standing dead ash, about 40 layers of soft, orange shelves. They smell amazing. These too leave me wondering how widespread the mycelia are. If I could strip everything from the tree but the mycelia, what would I see? There is a tool for visualizing mycelia on a small scale using florescence in situ hybridization3; could we do it on a large scale? How would our impression of the woods be changed if everything were dissolved but the fungi for just a moment? Even the non-fungal bits of the soil? We might find we were standing on a filamentous cloud that runs everywhere, places that even plant roots can’t go, tying them all together4.

On the trail that runs past the backyards on the west edge of the forest, I looked closely at a sugar maple. Earlier in the week I had started picking through The Hidden Life of Trees5, in which the author, a forester, discusses aging a tree that was less than an inch in diameter but turned out to be roughly 80 years old. It has been years since I was in the habit of counting growth rings on sugar maple branches, a practice inspired by conversations with Virginia Kline about her research in the Kickapoo River Valley6. I had forgotten how old they can be. I counted growth rings on this tree and found that a lateral branch about one and a half times as long as my middle finger and only a few millimeters in diameter was eight years old. That’s a remarkable amount of time to spend growing so little, a testament to what a maple can put up with.

I walked off-trail toward the middle of the woods and came across a dusting of bur oak leaves peppered with last year’s acorn caps and a few of this year’s caps, nuts gone. I found two with intact nuts. One was in fine shape, and I left it to germinate or get eaten. The other was split into three partitions at the stylar end, revealing a small pearly radicle, about half as large as a grain of rice. The flesh exposed between the cracks in the acorn wall was partly eaten by insects, but I think this one might have a chance. It’s the first bur oak I’ve seen germinating this year. Unlike sugar maples, bur oaks can’t tolerate many years in the shade. I see the seedlings in the understory every once in awhile, and they are rarely over a couple of years old. Beyond that, the cotyledons have nothing left to give, and the shade wears them down.

But perhaps this tree knows what it’s doing. Perhaps a squirrel will move this nut to a nearby opening and somehow not break off the growing root. I set it back in the soil right where I found it and hope for the best.


References

1 Cameron, Roderick. 2019. Eating Acorns to Save the World. From the International Oak Society Blog, 2019-08-07, accessed 2019-09-22. url: https://www.internationaloaksociety.org/content/eating-acorns-save-world
2 Chasse, Beatrice. 2015. Eating Acorns: What Story Do the Distant, Far, and Near Past Tell Us, and Why? International Oaks 27: 107–135.
3 NAKADA, Yuji, Satoshi NAKABA, Hiroshi MATSUNAGA, Ryo FUNADA & Makoto YOSHIDA. 2013. Visualization of the Mycelia of Wood-Rotting Fungi by Fluorescence in-Situ Hybridization Using a Peptide Nucleic Acid Probe. Bioscience, Biotechnology, and Biochemistry 77: 405-408.
4 If you haven’t read about Suzanne Simard’s exciting foundational research on how fungi facilitate movement of nutrients between trees, even trees of different species, check out her TED talk: How trees talk to each other.
5 Wohlleben, Peter. 2016. The Hidden Life of Trees: What They Feel, How They Communicate―Discoveries from A Secret World. Greystone Books.
6 For Virginia Kline’s doctoral dissertation on the Kickapoo River Valley and a host of other slides and documents from her life’s work, see https://uwdc.library.wisc.edu/collections/econatres/klinev/.

What broadens the world

He tried to tell his freshmen the simplest things–why a deceptive cadence makes a listener ache or how a triplet rhythm creates suspense or what makes a modulation to a relative minor broaden the world–and found he didn’t know.
— Richard Powers, Orfeo

Acorns have begun to fall in earnest, and Monday the chipmunks were racing across the trails with their cheeks packed full. Some bur oaks are raining acorns, others are mostly green, but most are halfway-ripe. The white oaks have started dropping acorns, and swamp white oak acorns are swollen on the street trees in our neighborhood. Red oaks have been shedding nuts for a few weeks. Monday, Jack-in-the-pulpit inflorescences were as multicolored as flint corn. Half of the false Solomon’s seal berries were ripe, the other half salmon colored. Carrion flower berries were almost black, and Joe-pye weed flowerheads were feathery with ripening achenes. Tufts of pappus were extruded from the tips of the flowerheads on the 6 to 8-foot tall wild lettuce–perhaps taller, but I did not go far off trail to check. Big-leaf aster and zigzag goldenrod were in bloom. Beak grass grains were hard between the teeth. The honewort schizocarps were fat and football-shaped, leathery, hard like nutlets, not yet brittle. Dryad’s saddle was darkening on the same tree where I had found it in late July last year, Crepidotus was sliming across the surface of fallen logs, and a soft, white, doughy fungus I do not recognize was sprouting from the woodchips. The jewelweed was becoming ratty, leaves torn and chewed and crisscrossed with slug tracks. The ephemeral frog pond just north of the spruce plot was dry.

I returned to the same paths on Friday. Thunderstorms had rolled through from about 4:00 to 6:30 that morning, shaking full red oak acorns and ripe walnuts to the ground. About half of the bur oak acorns falling looked to me to be viable, the other half perhaps aborted or weevil-infested. I doubt that the squirrels care, and the chipmunks were still racing around, capitalizing on the windfall. Even after the rains, the ephemeral pond was dry. Eastern wood pewees and crickets were almost all I heard aside from a few mosquitos and lethargic bees and lisping birds in the shrubs that I could not make out. If there were migrants–and there surely were–I wasn’t hearing them. Many plants were senescing. The most obvious to my eye were the variegated false Solomon’s seal and the yellowing leaves of enchanter’s nightshade, which I saw everywhere. Giant puffballs, which Christy Rollinson had reported the previous week, seemed to have erupted, along with scatterings of stump puffballs along the chipped trails. They have not yet to have started browning inside, though the epidermis of some of the stump puffballs is darkening. An enormous white jelly fungus on a fallen maple was turning creamy. The delicate, slender-stemmed Marasmius capillaris had emerged on a rotten log.

Galls on the wood nettles appear to have shifted from the leaves to the inflorescences. I first noticed them last year in late August, and I mistook them for fruits. This year, beginning in June, I was finding them on the leaves only, but now they have shifted back to the inflorescences. I have presumed that these were all formed by the same insect, Dasineura investita, but perhaps not. I can imagine two explanations for the move. First, it may be the same insect, ovipositing where resources are most concentrated. As the plant allocates sugars to the inflorescences, perhaps that is a better place to leave your children. This may be a second wave of the same insect, separated in time but not place. Second, this may be an entirely different insect, specializing on the inflorescence. I doubt it, but for no very good reason. I’ve neither reared them nor hunted down a good life history of gall midges.

Skeletons of silky wild rye stood along the trail edges, deceptive, few florets persisting among the long-awned glumes that will persist into winter. The ray flowers on the woodland sunflower had almost all dropped, leaving terse little heads of disc flowers to ripen in the understory. False nettle fruits were ripe, crunchy, similar in size and texture to smallish grains of uncooked quinoa (no relation: quinoa is an amaranth and spinach relative), standing close by the climbing false buckwheat, whose winged fruits are covering any tall plant it scrambles up in late season exuberance. Fragrant bedstraw was still fruiting. White rattlesnake-root was in full flower in the openings, elm-leaf goldenrod along the shadier edges, flowers lined up along the arching inflorescence axes like the trails of shooting stars. The first flowers were blooming on calico and Drummond’s aster. The yellow giant hyssop was flowering. Doll’s eye berries were blackening on the stem if they weren’t ripe and ready to go. Pokeweed berries on some plants were as dark as plums. Wild sarsaparilla and American elm leaves were turning.

Yesterday morning, Saturday, I headed to Maple Grove Forest preserve to find the bridge covered with the dusty webs of funnel-weavers. Did they appear over the course of a single week? As old as they looked, I thought they were abandoned, but each one on closer look was occupied. I’d find the spiders only when I moved slowly, inched my way in. Sensing me, each spider would retreat smoothly down the neck of its funnel and be no more than a gray shadow behind the webbing. In the St. Joseph Creek floodplain, elderberries have almost all fallen, leaving lacy raceme branches. Wingstem is still blooming, and bumblebees are still buzzing into jewelweed flowers. White snakeroot has just started to produce plumes of seed, but only where it stands exposed to the sun.

There are new fungi to see this week. Aborted entoloma appear to have erupted from the soil in just the past few days, sprouting up beneath the leaf litter like manna. This white, bumpy thing is found in at least a few patches in Maple Grove Forest Preserve right now. Research1 suggests it is most likely a pathogen of the honey mushroom, which I’ll have my eyes open for now that I realize these two go together. What I believe to be golden chanterelles are emerging from the soil right now as well. On a fallen tree, I came across an entire series of shelf fungi that I think are artist’s brackets, ranging from the first-emergent white edges to fully formed fruiting bodies. One of them appeared to be exuding black ink. On rotten logs you can still find orange mycenas, which I’ll never tire of, and from the same genus another but relatively nondescript bonnet. But not unexciting! For a few of the bonnets I found had been parasitized by another fungus, the bonnet mold, which lives off of the bonnet and produces spore-bearing hyphae from the bonnet cap, making the cap look like it has sprouted a beard. Will it reduce the cap to slime? Another whole set of lives going on beneath our noses that I knew nothing about before this weekend.

Wild leek is producing its black seeds, which are hardening up but still enclosed in the papery sheaths. Squirrels are ravaging the red oak acorns, but they are not getting them all: I came across a seedling of what I take to be bur oak from last year’s crop, one that most likely was cached but forgotten. Great horned owls are calling. Leaf miners (Cerodontha, though the species is unknown) have etched road maps into the white bear sedge leaves. Wild ginger leaves are edged with yellow, sprawling, a sure sign that days are growing shorter and cooler. Tearthumb is in bloom. I found what I thought at first were fresh basswood seeds under a tree, but they appeared on opening to be pithy inside, like galls. I need to find more to see what they really are. Beneath another tree a single oak apple gall had fallen. Berries were mostly dislodged from the Jack-in-the-pulpit plants I passed. One Jack I passed was covered with desiccated fruits. Touching them, I roused a male spider who trained his attentions on the stem ahead of him, then turned and readied himself for a fight, pedipalps cocked. Blue cohosh seeds are bright blue, the seed coats membranous, tearing easily. Large-flowered bellwort leaves are variegated. The sedges are still looking good, as sedges always do: Carex jamesii hummocks are deep green, lush, and scrawny little Carex radiata has sent up a flush of young leaves at the center of a spray of flattened culms splayed out around the base of the plant.

Saturday night was the opening for a show that Rachel curated at Lillstreet Art Center. Near the end of the evening, we stood on the rooftop garden with friends and watched the sky growing dark. Everything was dim and monochromatic, and at one point we realized with surprise that a bump we were looking at on the parapet was a katydid. As Rachel got close enough for a photo it clicked for her. We recognized the call, which we had suspected was a katydid but didn’t know for sure till now. It flew out over Montrose.

Look at all these individual moments over the course of a single week, crammed into the margins of the mornings, evenings, weekends. Whatever it is that made me study sedges, whatever it is that makes me want to go for walks and turn over logs, the same thing will make me replay this moment over and over, watching with my wife as the katydid disappears into the city night. I’ll have it with me 50 years hence. These instances broaden the world. Who can say why?


Plants referenced:

  • Actaea pachypoda – white baneberry
  • Agastache nepetoides – yellow giant hyssop
  • Allium tricoccum – small white leek
  • Aralia nudicaulis – wild sarsaparilla
  • Arisaema triphyllum – Jack-in-the-pulpit
  • Asarum canadense – Canadian wild ginger
  • Boehmeria cylindrica – false nettle
  • Carex jamesii – James’ Sedge
  • Carex radiata – bracted sedge
  • Caulophyllum thalictroides – blue cohosh
  • Circaea canadensis – broadleaf enchanter’s nightshade
  • Cryptotaenia canadensis – honewort
  • Diarrhena obovata – Beak Grass
  • Elymus villosus – silky wild rye
  • Eurybia macrophylla – large-leaved aster
  • Eutrochium purpureum – Sweet Joe-Pye-weed
  • Fallopia scandens – climbing false buckwheat
  • Galium triflorum – fragrant bedstraw
  • Helianthus divaricatus – woodland sunflower
  • Impatiens pallida – pale jewelweed
  • Juglans nigra – eastern black walnut
  • Lactuca biennis – tall blue lettuce
  • Maianthemum racemosum – false Solomon’s seal
  • Nabalus albus – white rattlesnakeroot
  • Persicaria sagittata – arrow-leaved tearthumb
  • Phytolacca americana – American pokeweed
  • Quercus macrocarpa – bur oak
  • Quercus rubra – northern red oak
  • Sambucus canadensis – American black elderberry
  • Smilax – greenbriers
  • Solidago flexicaulis – broad-leaved goldenrod
  • Solidago ulmifolia – elm-leaved goldenrod
  • Symphyotrichum lateriflorum – calico aster
  • Tilia americana – basswood
  • Ulmus americana – American elm
  • Uvularia grandiflora – largeflower bellwort
  • Verbesina alternifolia – wingstem

References cited

1 Lindner Czederpiltz, Daniel L., Thomas J. Volk, and Harold H. Burdsall, Jr. 2001. Field observations and inoculation experiments to determine the nature of the carpophoroids associated with Entoloma abortivum and Armillaria. Mycologia 93: 841-851. For a great summary: http://botit.botany.wisc.edu/toms_fungi/sep2006.html [accessed 2019-09-15].

Around the year in Maple Grove Forest Preserve

This post is the transcript of a 6 minute, 40 second presentation I delivered on September 7, 2019 at the Downers Grove Art Department’s PechaKucha, an event in support of the Downers Grove art community. The evening featured 7 speakers on a wide range of topics, from a Downers Grove resident who became an internationally-known opera star to competitive diving and biohacking.

For more on The Art Department, a subcommittee of the Downers Grove Marchers, and the great work they are doing to foster the arts and dialogue in Downers Grove, visit their public Facebook Page.

Around the year in Maple Grove Forest Preserve

[1] If you walk west from Emmet’s Pub by the straightest route you can, cut through the parking lot across from Immanuel Lutheran Church to Brook Lane and Turvey Road, you’ll reach the edge of Maple Forest Preserve, an 80-acre sugar maple forest purchased from Marshall Field III by the Village of Downers Grove 99 years ago. I find something new there every week.

[2] 2019 started too warm. By Christmas, spring beauty corms had already started putting out shoots and straplike leaves. This species is a spring ephemeral, built to grow fast, sop up sun and vitamins, flower, set seed and die back before the tree canopy leafs out. This year’s shoots emerged about three and a half months early.

[3] Perhaps more surprising was the false rue anemone, looking on January fifth as I’d expect to find it in mid March. Slower to flower, it should be less nimble than the ephemerals. That same day I found wood violets, wild ginger shoots, earthworms churning the soil. Human-caused climate change is an experiment whose outcomes will continue to surprise us.

[4] A week later, there was snow, thankfully, because by the end of the month the bitter cold had arrived. Snowpack helps plants, insects and spiders, earthworms and small mammals survive the coldest weeks of winter. Its crystalline arms interlink to form an insulating blanket, the base of which evaporates away as the earth warms it, leaving a gap for life at the forest floor.

[5] Mice and meadow voles party under the snow all winter long, gnawing at deer antlers and leg bones, living on cached seeds and tree bark. Owls and coyotes can hear them through the snow, but they are safer underneath than above. Still, their trips up top become inscribed in the snow as they gallop the length of a fallen log or snowplow between burrows.

[6] A downed tree in January reveals dark zone lines that fungi lay down at their frontiers. The fungi are devouring the dark lignin that makes plant cell walls rigid, leaving the rotted wood white. We see the fungus bodies, but it is the white rot that shapes the forest, transforming wood into soil while we’re inside reading and listening to the radio.

[7] Honey mushroom rhizomorphs similarly become visible as bark disintegrates from a fallen oak tree. During the growing season, they invade roots of uninfected trees and work their way up beneath the bark, where the fungus infects the wood and causes decay. They aren’t more prevalent in the winter, but they are obvious even when the edible mushrooms aren’t visible.

[8] By mid March we start seeing spring wildflowers. They all have their strategies. False mermaid germinates in late fall, then emerges as a seedling in early March. It absorbs as much sunlight as it can through April, forms green carpets in the forest understory, sets seed, then dies back as the leaves come out on the trees, leaving trails of yellow foliage and warty nutlets.

[9] Wild leek takes a different tack. It’s a spring ephemeral, spreading broad, thin leaves in March through May that wither as the trees leaf out. You’ll think perhaps that you’ve missed the flowers, but watch for the scapes in early July: after 7 weeks of nothing, they’ll emerge, come into full flower by the end of July, and form dark seeds near the end of August.

[10] Other wildflowers take a longer view. Wild ginger doesn’t emerge until 3 or 4 weeks after the false mermaid. The leaves unfurl as they loose themselves from the soil, then produce a raw-meat colored flower at the soil’s surface. The berries ripen by mid June, seeds crested with a nutritious elaiosome that entices ants to drag them into new territory.

[11] As spring wildflowers peak, songbirds migrate, taking advantage of the insects awakening in the warming canopy and tree bark and the opening buds. Most visible among them are the warblers, which in spring are in their glory, singing and in full color. They are vulnerable, too. This black-and-white warbler struck our window at the Arboretum, but recovered to fly away.

[12] June arrives with an onslaught of sedges. There are roughly 140 species in the Chicago region, and they are in every habitat. Carex davisii was my favorite sedge find of the summer, one of only two populations known in the county. Knowing the sedges, wrote Annie Dillard, makes the “least journey into the world… a field trip, a series of happy recognitions.”

[13] The first of July this year I came across a spongy fallen maple bristling with what appeared to be bright red, tiny toadstools with caps less than a millimeter in diameter and threadlike stalks. I posted the photos online and heard within hours from a Tasmanian naturalist that they were in fact slime molds, protoplasm lurking in open sight.

[14] I’d been missing a whole branch of the tree of life on my walks. Two days later I returned to find at least five species: pin-sized “toadstools,” mungbean-sized “puffballs,” grains of rice suspended by threads, pincushions on the sides of logs, an undifferentiated yellow plasmodium. Next year, I’m hoping for slime molds everywhere.

[15] In August, jewelweed spreads its leaves like a bridge between spring and fall, forming hummocks in the floodplain of St Joseph Creek, bearing open-pollinated flowers, closed flowers that can only self-pollinate, explosive fruits, and gall midges wrapped up in blisters along the leaf midvein or wrapped tight in galls that dangle like chickpeas from the shoot tips.

[16] By end of summer, leaf-miners have etched trails across elm-leaved goldenrod, white snakeroot, and white bear sedge, which looks like a monochromatic map of the London Underground. Joe-pye weed leaves are rolled and chewed and mined. Cavities in the elm leaves rattle as though they were enclosed in cigarette paper. Jewelweed leaves are a tangle of slug tracks.

[17] What will come next? It’s fungus season, and as September burns on toward the first frost, puffballs spread out across the forest floor and brown and dry out, spreading spores at a slap or stomp, if they don’t get collected fresh and cooked up. Chicken of the woods and orange mycena emerge from decomposing trees beside white jelly fungi. The year gives way to rot.

[18] In the coming months, the seeds of late summer and fall will ripen and disperse. American pokeweed berries will darken like plums over the coming weeks. Elderberries already have. Acorns are ripening on the bur and white and Hill’s oaks, and they are falling from the red oaks. Joe-pye weed achenes will fly away as October comes on.

[19] Before we know it, chlorophyll will break down in the sugar maple leaves, exposing the xanthophylls, carotenes, anthocyanins that form the yellows, oranges and reds that we flock to the woods to see. If the tree has time, at the base of each petiole will form an abscission layer that cleaves the leaf from the tree and seals the scar in one stroke. Fall will have ended.

[20] Then winter will begin again, and as the squirrels gather acorns they cached in September, there will be new things to see, each and every day. I could spend my whole life exploring this 80-acre forest down the street and still have more to learn. One good forest is enough for a lifetime.


For additional reading on a few of the slides above:

[1-3] The account of this winter’s precocious spring wildflowers is written up in my January 6 blog post, with photos and identifications.

[6] The Wikipedia article on spalting describes different causes of fungal wood discoloration, and explains in brief how zone lines are formed by white rot fungi.

[12] My post Various forms of happiness describes this past year’s sedge season, with photos and identification of severl of Maple Grove’s species.

[13] Cohen, Arthur Le Roy. 1969. Slime molds (slime fungi). In: Encyclopaedia Brittanica, Volume 20. William Benton, Publisher, Chicago. Also, my post What Fiction Could Only Imagine, on the slime molds of Maple Grove

[19] An outstanding article by Ted Levin, “The Causes of Fall Color,” from Northern Woodlands, 2002.