30 million years of sedges

“I would like to know grasses and sedges—and care. Then my least journey into the world would be a field trip, a series of happy recognitions.” — Annie Dillard

January 30, 2017

This morning was cold and clear, though nowhere near as cold as it was four weeks ago when I started this journal. When I arrived at the gate, the big dipper was tipped on end, mouth open toward the north. I think the stars were already becoming a obscured by predawn light at about 5:30, but this could have been my imagination. In a couple of months I’ll be able to start looking for warblers and wildflowers on the ride in… sunrise will be at 6:30 then, and I’ll have at least a little light before I get to my office.

I biked around the east end of the road to the trailhead where I have been looking for Carex woodii the last two weeks. I finally found it last week while my colleague Matthias was in town from Germany for a meeting of sedge researchers. Matthias is a remarkably focused man, good with data, a good field botanist, and clear about what he wants to know. On this trip he wanted to know when sedges are producing their flowers. Do they start to produce in the spring, minimizing the risk of freezing or burning off young inflorescences before they can do their thing in May and June? Or do they produce in the fall, so they can hit the ground running when the temperatures rise? I had had the best intentions of flagging specimens so that we could find them under the snow, but I didn’t get to it. Fortunately, we had no snow, and Monday morning last week we walked the best woodland sedge loop in the Arboretum. We found broad leaves of white bear sedge (Carex albursina) in the leaf litter around Parking Lot 8, first a few, then everywhere. They were a muted green. We found what I believed to be Carex cephalophora, but I could not be certain, so we didn’t collect it. We found Carex hirtifolia with the hairs worn off the leaves, but fine soil hanging to the plant bases where the stubby broken-off hairs persisted. We found trampled-down Carex rosea and the pale rubbery bases of Carex blanda; the tall, glossy shoots of Carex grisea; possibly Carex granularis (I don’t know what else it could have been, but the location surprised me); grassy Carex pensylvanica scattered in every section of the woods; emerald-green shocks of Carex jamesii, whose leaves appeared to me to be at least 50% longer than they are at fruiting time… I’ll have to watch this summer to see if memory is misleading me. The C. jamesii was particularly satisfying, as we took some time working our way from patch to patch in search of inflorescences, until we found one with ripe perigynia—the sacks that surround the seed-enclosing achene inside—hanging on from last June. Was the achene still viable? Sedges are mostly not creative seed-dispersers: the majority of species drop their perigynia right at their feet, where they may get stuck in the mud on a duck’s foot if they are lucky, or eaten by a mouse. Some appear to have elaiosomes at their bases, food for ants, who carry them off to plant in their nitrogen-rich mounds. Some have inflated perigynia for flotation, some have juicy perigynia for ingestion by small mammals or birds, some have wings or hooks at the ends that allow them to stick on the legs of passers-by. But mostly they are just fallers.

What they lack in dispersal strategy the woodland sedges appear to make up for in evergreenness. From what I could see, every sedge above was evergreen, with the possible exception of Carex rosea and C. cephalophora. This was not the case in the wetlands where we stopped before we got to the woods. We parked first by the crabapple collection and walked the margin in search of Carex comosa. It was there with its feet in standing water at the west edge of the lake, but neither Matthias nor I had boots on. We intended to come back for it later but never did, as Matthias turned out to have more material than he could work on for this trip by the end of the day. We walked to the pond on the other side of the road to collect the hairy-sheathed Carex atherodes. Both plants were as brown as could be, though I believe there were young shoots coming up from the base of the C. atherodes we collected. We drove on to the pond nestled between the woods and oak collection, and there I tried for five minutes to chip the lake sedge Carex lacustris out of the ice, which was not a fruitful enterprise, before I retreated 15 feet uphill to a patch that was creeping onto the adjacent bank: fresh shoots coming up, but otherwise brown. There was a bedraggled patch of Carex tribuloides in the grass that was also brown. I wondered whether these wetland sedges, because their roots are in solid ice much of the winter, might have less available water through the winter months. Would this make it riskier to be evergreen?

After lunch and some paperwork, Matthias and his student Sebastian met me back at my house, where we picked up a number of out-of-place sedges: Carex eburnea of the white cedar glades; C. sprengelii and C. gracillima of the maple forests; C. lupulina of rich ditches and bottomland forests; C. trichocarpa of sedge meadows and the wettest of prairies; C. typhina or C. squarrosa of wet woods, I’ve forgotten now which one; C. brevior of dry prairies. I believe all were green except for C. trichocarpa and C. brevior. I’ll have to look again when I get home tonight. It may be a woodland phenomenon, an adaptation to life in the shade and the resultant need to get going early in the spring.

The next morning I pulled off the road one more time to find C. woodii, and I did find it, right where I knew it should be but had somehow not seen in the previous two weeks. I found had been looking for the wrong thing, imagining May shoots when in fact the plant is more subdued this time of year than I had imagined it would be. I brought a healthy plant back for Matthias. He dissected the staminate spike and brought it out to me to see. It was the slenderest, freshest, whitest young shoot you could hope for, practically a naked meristem, clearly formed in the fall, waiting all winter for its shot at reproduction in May. I’ll think differently about all these sedges now, having gone hunting for them in winter.

The remaining days of last week were spent studying the sedge tree of life with colleagues from seven countries, making our first steps at a new classification. Much of the time was spent conversing about what the species look like, and why species classified under a variety of old section names might or might not belong together in a particular lineage. In our walk on Monday, Matthias and I had covered nearly 30 million years of sedge evolutionary history. The species we’d collected had arisen from lineages scattered across the sedge phylogeny, lineages most of us in the group have known for a long time under formal or informal names: the bladder sedges; the woodland danglers; section Ovales; the caricoid sedges; sections Laxiflorae and Paniceae, partially interdigitated; the “rosea” group of subgenus Vignea. But with so much knowledge in that room, so many decades of cumulative experience studying sedges (by my back-of-the-envelope estimate, we had between 270 and 300 years of sedge-hunting under our belt as a group), we attacked more of that tree than Matthias and I could ever get to on our own. Among us we had hunted for sedges in Vietnam, China, Russia, Japan, Mexico, Andean South America, the Venezuelan Tepuis, the western Himalayas, Korea, New Zealand, Australia, western North America, Eastern and southeastern North America, Alaska, Hawaii, and probably a host of places I am not even aware of. It was a romp through the woods on a deep-time and broad-geographic scale.

It’s a funny thing about this line of work, and much of what I love about it, and part of what drives me nuts. I’ll be thinking of populations diverging from each other millions of years ago when I am in the woods in mid April this year, watching the sedges come up and flower come out on the oaks. What a blessing! To be able to back in time like that and understand by such long perspective things we are looking at today. But at the same time, when I get to the gate in the early morning and the stars are so beautiful overhead, there’s a constant din in the back of my mind from all this analyzing and writing and trying to figure out inside what’s gone on outside. I guess it’s a small price to pay for being able to learn so much, and it’s a price I pay willingly. Once you learn something, you never see the world the same again. I think you simply don’t have the option.

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