perigynia: Carex swanii

On Wednesday I was doing some work in one of our meadows and came across a sedge that looked a little odd to me - I was pretty sure that I had not seen it before so I plucked a culm and threw it in my bag. When I keyed it out at the end of the day it easily went right to Carex bushii (Bush's sedge) a threatened species in Ohio. This was exciting considering the fact that no records exist for C. bushii in this county, so on Thursday I headed back out to find the plant and get a proper sample to press. I headed to the area and quickly found a nice patch of sedges that looked similar but not exactly like the one I collected the day before. I collected some and keyed them out using Field Manual of Michigan Flora this time the sedge keyed out to C. bushii but not as smoothly as before. Using the key I quickly made it to the Porocystis (Virescentes) group and ruled out C. swanii and C. virescens due to the galbrous perigynia on this species. The terminal spike was pistillate at the apex ruling out C. pallescens (also growing in this field), so the only two choices left were C. bushii and C. hirsutella a tough call because the scales were visible but just barley sticking out beyond the perigynia - C. hirsutella is said to be awnless or with an awn less than 0.5mm since these awns were longer I hesitantly landed at C. bushii again but I was sure that this was different than the sedge that I had seen the day before.

Not happy with the result I looked in Vascular Plants of Ohio and in Gleason and Cronquist and found that another species within this group exists in Ohio but not in Michigan - no wonder the key didn't seem to fit. I ran the plant through Gleason and Cronquist: terminal spike pistillate at top staminate below, perigynia glabrous, perigynia spreading (not appressed and ascending). This took me to two species C. bushii and C. caroliniana with the differences in hairiness of the sheath and length of the scale. This specimen has hair all the way around the sheath but it is very sparse and again the scales are about even with the perigynia but not as long as they should be for C. bushii. I was still confused. Next I ran it through the Vascular Plants of Ohio key: perigynia glabrous, terminal spike staminate only at base, blades glabrous sheaths pubescent and perigynia plump – this took me to C. caroliniana. If the blades were pubescent and the perigynia flattened I would have ended at C. hirsutella. OK so I finally keyed it out to C. caroliniana but I was not satisfied because this key was missing C. bushii.

I decided to look in Vascular Flora of Illinois and not only were all three (C. bushii, C. hirsutella and C. caroliniana) included in the key but they are the last three listed in the Group 1 section (sedges with hairy parigynia, sheaths and/or leaves), here is the end of the key:

Leaves very sparsely hairy…………………………………………………..................................................................................................C. caroliniana
Leaves moderately to copiously hairy
Pistillate scales lanceolate, acuminate to awned, longer than the perigynia; perigynia rounded on all faces and strongly nerved………………………………......................................................................................................................................................................C. bushii
Pistillate scales ovate, acute to cuspidate, shorter than the perigynia; perigynia with flat, inner face, weakly nerved…………………………………………................................................................................................................................................C. hirsutella

Using the Illinois key I was satisfied that I had found C. bushii on Wednesday and C. caroliniana on Thursday. I spent the rest of Thursday looking for the sedge that keyed so smoothly to C. bushii but I could find nothing but the sedge that I am now calling C. caroliniana.

Finally on Friday morning I retraced my path from Wednesday and located the sedge, once again it keyed very quickly to C. bushii. Looking around I found examples of what I believe to be C. bushii, C. caroliniana, C. hirsutella and C. pallescens – here is a photo that I made of the four plants.