Late-summer jewelweed

17 August 2024
Pale jewelweed is mounded high in the floodplain of St. Joseph Creek. Its undulating surface forms a landscape that does not parallel the ground, but instead creates a smoother surface hovering above. With their roots in the soil, the jewelweed plants grow in proportion to the intensity of light streaking in between the trees: stronger light, taller jewelweed.[1] Thus the surface of the jewelweed integrates over the deep history of earth, which laid down the bedrock over the course of billions of years; the glacial history that shaped the landforms over the past 2.6 million years; the last 15,000 years of floods, erosion, and soil formation that put the final touches on the land we see today; and the light environment shaped by the vagaries of competition, disease, windthrow, frosts and droughts, pollination and germination every year and every day. These processes together form the land and the forest that clothes it. Jewelweed responds to this entire history.

Step carefully between the stalks, and the jewelweed canopy closes around you. The stems are as big around as my pinky, the joints tough and thickened like gouty knuckles. The light cascades pale green through the leaves above. The air is moist and still, like being inside an organism. Hidden within this dimly lit room is the decomposing bole of a severed red oak, shingled over with turkey tail fungus, peppered with tiny fungal caps. The jewelweed forest reminds me of the densely-planted, narrow-trunked oak forest in the southwest corner of the UW Madison Arboretum’s Grady Tract, planted by a caretaker in, I believe, the 1940s. The trees there have grown up dense and suppressed, and little grows beneath them (so far as I remember; I was last in that forest well over a decade ago). The understory beneath the jewelweed is about as sparse: a goldenrod, a spindly honewort in fruit, and a few wood nettles grow here, little else.

Where Brooklyn and I enter from the Gilbert Park parking lot this morning, Maple Grove is framed by an orb-weaver suspended between young sugar maples. Opened, outcrossing flowers whose spurs still hold a drizzle of nectar are strewn across the jewelweed landscape. They rub shoulders with lima-bean sized cleistogamous flowers, which are clamped shut, closed to pollen from the outside world, obligate self-pollinators. Cleistogamous flowers are a failsafe, a way of ensuring that seeds get into the next generation if pollination is poor, but at a cost: self-pollinated flowers give rise to seeds that germinate less reliably, and seedlings that die more quickly and grow more slowly, on average, than the out-crossed seeds.[2] The flowers are interspersed with turgid capsules; with a light squeeze at the base, the fruit walls recoil explosively, spitting seeds across the trail. The jewelweed canopy is pierced with wood nettle inflorescences. Along its edge are flowering white snakeroot and the dregs of tall bellflower.

Brooklyn and I cross the footbridge over St. Joseph Creek, stepping up and over as the floodplain floor slopes downward beneath us, until the bridge railing comes almost equal to the upper margin of the jewelweed. Bringing my eyes down to the level of the railing, I feel like a canopy explorer, like Nalini Nadkarni or Meg Lowman may have felt their first times up in the tree canopy—what one might call the “real canopy,” though this one is real as well, buzzing with bees and speckled with raindrops. Wingstem and cutleaf coneflower are blooming, superficially similar in appearance today, with straplike, spidery, twisted petals slightly pinched at the tips. South of the bridge, giant ragweed towers over the jewelweed plants, roughly twice their height. An evening primrose stands six feet tall on the riverbank. Along the edge of the bridge grows what I take to be horseweed, downy with seeds. The river is turbid and a bit high from last night’s rain. Brooklyn will not pass until I let her get into the water. She drags me partway into the water. White bear sedge leaves are frayed by the summer, but they still have months of work ahead before they retire. Most will make it all the way through the winter to get the plant to next year’s young leaves.

Brooklyn jumps onto the great sugar maple bole that fell across the trail a couple of years ago. I crawl over it gracelessly. There are still 17-year cicada holes punched into the muddy trail. Jumpseed spikes studded with brittle white seeds line the trails. We climb the slope behind the houses on the east edge of the preserve. A jogger runs through on the main trail down to our left, pushing a stroller and playing music loudly. The jogger’s music fades off to the south, only to be replaced by hammers at work on the houses to our right. They punctuate the sustained purr of the crickets.

Great blue lobelia is flowering in the low areas along the trail. A stand of bottlebrush grass pooled at the base of the hill has dropped a quarter of its seeds, and the rest release easily at a touch. Pokeweed flowers are turning gradually into hard fruits. False nettle is stout with inflorescences. Late boneset is in full flower. Elm-leaf goldenrod flowers are in bud. Mayapples have almost completely given up: most are pale, many are stooped, some are kneeling already beneath the still-growing trees, surrounded by the red oak acorns that were pollinated last year, fertilized and developed this year, and that will germinate next spring. Early-falling leaves and plants are bedding into the litter that will nourish and insulate the roots and rhizomes of the understory through to next year.

The narrow-leaved wild leek seeds have almost all dropped. A few are still nestled into their capsules, valves flexed open, the seed coat black and glossy as a marble. On most plants, even the residue of the flowers is gone, leaving only the pedicels. The broad-leaved wild leek seeds are still ripening, however. I squeeze the green capsules that surround them and feel the seed coat give way, the pulp inside squeezing out. Scratch away the fruit wall, and you find the seed glistening inside, hardening up. A few seeds have been devoured by insects. On one plant, I find a hole drilled through the capsule and the seed inside gone. Another capsule has been chewed open from the top, and half of the seed coat persists like the remnant of a soft-boiled egg in an egg-cup, the insides eaten out, the lower half of the shell seated comfortably and untouched in the base of the capsule. It is as light as chaff.

A red-eyed vireo and an eastern wood pewee are calling as Brooklyn and I walk out. A pleated pluteus is growing from a rotted log by the parking lot. Crickets are still purring. Solomon’s plume is yellowing, bedraggled. Black snakeroot fruits are barely hanging on to the last days of summer.

Plants referenced

• Ageratina altissima — white snakeroot
• Allium burdickii — narrow-leaved wild leek
• Allium tricoccum — broad-leaved wild leek
• Boehmeria cylindrica — false nettle
• Campanulastrum americanum — tall bellflower
• Carex albursina — white bear sedge
• Cryptotaenia canadensis — honewort
• Erigeron canadensis — horseweed
• Eupatorium serotinum — late boneset
• Impatiens pallida — pale jewelweed
• Laportea canadensis — wood nettle
• Lobelia siphilitica — great blue lobelia
• Maianthemum racemosum — Solomon’s plume
• Persicaria virginiana — jumpseed
• Phytolacca americana — pokeweed
• Podophyllum peltatum — mayapple
• Quercus rubra — red oak
• Rudbeckia laciniata — cutleaf coneflower
• Sanicula sp. — black snakeroot; I have never been confident about which species I am looking at, so I’ll leave these at Sanicula for the time being
• Solidago ulmifolia — elm-leaf goldenrod
• Solidago sp. — goldenrod (not identified to species)
• Verbesina alternifolia — wingstem

References cited

[1] John Curtis wrote about this phenomenon in 1959; see my previous post, “Stumbling into the universe by chance,” for the quote and citation.
[2] Waller DM. 1984. Differences in Fitness Between Seedlings Derived from Cleistogamous and Chasmogamous Flowers in Impatiens capensis. Evolution 38: 427–440.