A Recap of the First Annual Wisconsin Sedge-a-Thon
- Nate Martineau
- Jun 10
- 13 min read
Updated: Jun 10
Southcentral Wisconsin - June 8th, 2025
Over the weekend, a small group of Wisconsin botanists gathered to test out the concept of a sedge-a-thon. Alex Graeff, Mary Ann Feist, Kevin Doyle, Rob Schubert and I visited four carefully selected sites representing the sand barrens and poor fens of the Central Sands, the rich forests of the Driftless Area, and the floodplains of the Lower Wisconsin River. The goal was to see as many "true sedge" (Carex) species as we could in one day. This is the largest plant genus in Wisconsin by a long shot, providing the right amount of challenge combined with the ability to tally up an impressive total. Each site had a completely different set of species, and by the end of the day we'd tallied 57! This is over a third of Wisconsin's 160ish species, setting an excellent baseline for future iterations in different areas of the state. There were great finds and non-Carex highlights throughout, making it an incredibly enjoyable experience.
Before the event officially started, I met up with Alex on the afternoon of the 7th in order to look at two extra sites. My notes for sedge-a-thon are for the 69 species I saw over the entire weekend, so that's what I'll recap here. As I recount the species we saw on the 8th, I will do my best to note where we saw any species the next day to provide a better picture of what we saw on the actual day of the event. For better context, I will also give general abundance and habitat information, as well as links to iNaturalist observations (not necessarily from this weekend) for each species.
The first site for Alex and I was a wonderful floodplain on the Wisconsin River just north of Steven's Point. It had wet swales, high ridges with sand prairies and oak savannas, and lower ridges with rich basswood-maple forest. Because of the huge variety in habitats, the sedge diversity was excellent. We saw:
1) Carex sprengelii- A common species of diverse habitats associated with rivers. It also happens to be my favorite Carex, which made it a strong start for the weekend. We did not see this on the 8th.
2) C. pensylvanica- Abundant in many habitats. Saw lots of it the next day.
3) C. grisea- Common in floodplains and moist woods. Seen later at Bass Hollow and Mazomanie.
4) C. intumescens- Abundant but slightly more northern in many habitats. Seen later at Mazomanie.
5) C. blanda- Abundant in many habitats. Seen later at Bass Hollow and Mazomanie.
6) C. tenera- Common in floodplains, savannas, and other woodlands. Plenty seen the next day. the first of many species in section Cyperoideae (the genus is split into recognizable sections to make keying easier) which had us all huddling over our keys throughout the weekend. This one is recognized by its small size, drooping inflorescence, and the tiny bumps (papillae) on its leaf sheaths.
7) C. radiata- Common in woodlands. Seen later at Mazomanie.
8) C. cephalophora- Common in woodlands. Seen later at Bass Hollow.
9) C. gracillima- Common in woodlands. Seen later at Bass Hollow and Mazomanie.
10) C. emoryi- Uncommon clonal species forming large swaths of arching leaves along riverbanks. Seen later at Mazomanie.
11) C. crinita- Common in wet places. Not seen on the 8th.
12) C. pellita- Common in sunny places. Plenty seen the next day.
13) C. deweyana- Common but a bit more northern in woodlands. Seen later at Bass Hollow.
14) C. vesicaria- Uncommon in places with fluctuating water levels. Not seen the next day.
15) C. tuckermanii- Uncommon in places with fluctuating water levels, especially floodplains. Instantly recognizable for its pale spikes of inflated perigynia, and one of my favorite sedges. Seen later at Mazomanie.
16) C. stipata- Common in wetlands. Saw lots the next day.
17) Carex arcta- Uncommon to rare in sedge meadows and the edges of forested wetlands. We found this more northern species in a wet, open swale below a ridge of oak savanna. This was only the second time I'd seen it! It's not found much farther south than this site, which lies on the transition zone between Wisconsin's northern and southern floristic regions. We did not see this species on the 8th.
18) C. bromoides- Common tufted species of woodlands with high or fluctuating water tables. Seen later at Mazomanie.
19) C. siccata- Common in dry prairies and barrens. Seen later at Quincy and Mazomanie.
20) C. umbellata- Common diminutive species on dry sand and bedrock. Not seen the next day.
This was a beautiful and extensive site which I will be sure to explore more thoroughly. I suspect there are more rarities to be found here. One we did find during our short visit was St. Lawrence Grapefern (Sceptridium rugulosum), a plant I've only seen once before. Three plants were growing in a small remnant of oak barrens next to the Wisconsin River. It is listed as special concern in Wisconsin.
Our next stop was one of a series of unique lakes 20 miles to the south. The wildly fluctuating shorelines and sandy lakebed here support a very rare Wisconsin endemic, which was our primary goal. It also offered eight new Carex species, some which thrive particularly well in this unusual habitat. They were:
21) Carex sychnocephala- Rare and seen during low water years on fluctuating shorelines. This is a bizarre sedge with its extremely narrow, densely packed perigynia and massive bracts, hardly looking like a Carex at all. This lake is home to one of only three populations I've ever seen. Not seen the next day.
22) C. viridula- Locally common species of wet, bare soil with little competition, often in calcium-rich (calcareous) soils. Later seen at the Dells ditch.
23) C. hystericina- Common in sunny wet places, especially where there is bare soil. Not seen on the 8th.
24) C. crawei- Rare in sandy and gravelly places with little competition, especially in highly calcareous places. Finding it away from a Great Lakes shoreline, exposed limestone, or fen habitat was new for me. Not seen the next day.
25) C. aurea- Uncommon in wet calcareous soil. Often difficult to tell from C. garberi (State Endangered) before its perigynia ripen to a distinctive yellowish-orange color. The plants we found here look a lot like C. garberi, with densely packed perigynia and quite a few perigynia at the ends of the terminal spikes. However, I do think they're C. aurea, because garberi just has a different gestalt that is hard to put into words. We saw this one again at the Dells ditch.
26) C. atherodes- Can be abundant in sedge meadows, riverbanks, and lakeshores with fluctuating water levels. I really like the leaf sheaths, which are both ladder-fibrillose and hairy. I don't see this species often; it seems to be very local. Not seen the next day.
27) C. crawfordii- uncommon on bare or disturbed wet soil, often on receding shorelines. Seen later at the Dells ditch. Another species in section Cyperoideae, recognized by its densely packed inflorescences and very narrow perigynia often less than 1 mm wide.
28) C. vulpinoidea- Common in many kinds of wetlands. Not seen the next day.
Despite all the interesting sedges, the highlight for me was the extremely rare Fassett's Locoweed (Oxytropis campestris var. chartacea), known only from about 20 Wisconsin lakes with similarly fluctuating water levels and sandy bottoms. Every one of these lakes was inundated by ridiculous amounts of rain in the late 2010s and early 2020s, but the locoweed only blooms when open sand and gravel are exposed by low water levels. These photos may represent the first time it's been seen flowering in seven years. What a treat to see this beautiful and rare species thriving after over half a decade underwater.
On the morning of the 8th, Alex and I woke up early at our campsite at Roche-a-Cri State Park and quickly climbed to the top of a large, isolated Cambrian sandstone outcrop, one of many in the region which were formerly islands in Glacial Lake Wisconsin. There we enjoyed nice views as well as Carex tonsa var. tonsa, the 29th sedge of the weekend. From there we drove to Quincy Bluff & Wetlands State Natural Area to meet up with Kevin and Mary Ann. We started the official sedge-a-thon on the roadsides, sand barrens, and poor fens of the Central Sands (the old bed of Glacial Lake Wisconsin) and racked up 19 sedge species. Fifteen of these were new for me and Alex:
30) Carex utriculata- Common in open wetlands, often in deeper water than most other sedges.
31) C. stricta- Abundant in all kinds of wetlands, as well as adjacent drier soil.
32) C. brevior- Common in dry to mesic sandy soil. Another from section Cyperoideae recognized by its fairly small & nearly circular perigynia, smooth sheaths, and inflorescences with 5+ spikelets that taper toward the base.
33) C. annectens- Uncommon in dry to moist open places, generally not in rich soil.
34) C. scoparia- Common in all kinds of wetlands, especially in bare or disturbed soil. Similar to C. crawfordii, but with less densely packed heads and slightly wider perigynia.
35) C. buxbaumii- Uncommon in calcareous wetlands, especially fens. One of the prettiest sedges.
36) C. muehlenbergii- Common on dry, bare sand.
37) C. bicknellii- Common in dry to mesic prairies. A member of section Cyperoideae easily recognized by its very large perigynia with coppery-colored "shoulders" just below the beaks.
38) C. aquatilis- Common in sedge meadows, peatlands, and other wetlands with deeper water.
39) C. lacustris- Common in all kinds of wetlands, especially sunny ones with deeper water.
40) C. oligosperma- Completely restricted to peatlands, where it can be common.
41) C. chordorrhiza- Uncommon in peatlands where it grows only on Sphagnum moss. One of our weirdest sedges, using rhizomes to creep along the ground and even through nearby vegetation.
42) C. lasiocarpa- Also restricted to peatlands, where it can be the dominant species across huge areas.
43) C. trisperma- Slightly more northern species of peatlands and mossy wooded wetlands.
44) C. brunnescens- Slightly more northern species of wooded wetlands.
The rain tapered off just as we left Quincy and blue sky was just starting to appear as we arrived at our next site, a unique ditch between a highway and railroad a little northwest of the Wisconsin Dells. This wetland caught my attention last year when I visited for a rare plant and noticed a number of interesting sedges. It did not disappoint us as it quickly provided seven new species for the day, including three that were new for me and Alex:
45) Carex conoidea- Uncommon in moist, sunny, sandy soil.
46) C. echinata- Uncommon in wet, acidic or peaty places.
47) C. haydenii- Uncommon in mesic to wet acidic soil, especially the upper edges of sedge meadows.
This site is unusual for a population of the very rare Wolf's Spikerush (Eleocharis wolfii), which we made sure to appreciate during our visit. It is distinctive among the spikerushes for having twisted bluish culms and baggy sheaths. Really cool and unexpected was a population of Seedbox (Ludwigia alternifolia), known to occur naturally in only a tiny handful of places in Wisconsin. Later in the season these will have four-petaled yellow flowers, but my favorite are the cube-shaped seed capsules from which it gets its common name.
By now the weather was gloriously mild and sunny, and we were on to Bass Hollow State Natural Area. The mesic forests and valleys here lie directly on the edge of the unglaciated sandstone and dolostone deposits of Driftless Area. Bass Hollow features a number of rich forest sedges as well as easily my favorite site of the trip: a nearly treeless shelf of seepy, muddy soil perched most of the way down the steep slopes of a stream valley. I have never seen anything like this elsewhere in the Driftless Area. The valley we botanized drains directly into the Central Sand Plains, which makes me wonder if at one time the edge of Glacial Lake Wisconsin deposited a layer of clay or silt, therefore creating the horizontal impermeable layer which is apparently present here. If this is true, the bottom of this slope is the exact boundary of the Driftless Area! This amazing formation padded our lists with a couple of rarities as well as some species which are normally found a bit farther north. Bass Hollow was overall quite productive. If my mental math serves, we saw 19 new species for the day, 14 of which Alex and I hadn't seen yet:
48) Carex rosea- Common in many kinds of woodlands. Very similar to Carex radiata.
49) C. sparganioides- Common in forests and savannas.
50) C. laxiculmis var. copulata- The more frequent variety (narrower bright green leaves) of a species that is quite uncommon in rich forests. Always a nice find.
51) C. scabrata- Common just to the east but rare to uncommon in Wisconsin, which is at the western edge of its range. The plants at Bass Hollow are nearly the southernmost in Wisconsin, but for a single known population in the Baraboo Hills. They are probably one of the many relicts of the Pleistocene glaciation which the Driftless is so famous for.
52) C. granularis- Common in all kinds of wet, especially calcareous soil.
53) C. tribuloides- Fairly common in wetlands of all kinds. A member of section Cyperoideae recognized by its baggy leaf sheaths, stiff inflorescences, tapered & ascending spikes, and longer and narrow perigynia than C. projecta and C. cristatella.
54) C. prasina- Rare on slopes and along streams in sloped, soggy, rich woods. Listed as Special Concern in Wisconsin and totally distinctive for its drooping spikes, pointed and often twisted perigynia. and densely clumped bluish leaves. Always an indication that you're in a really interesting place, and one of my absolute favorite Carex species.
55) C. normalis- Fairly common in open wetlands and moist woods. Another section Cyperoideae, identified by its tall and sparse culms, spreading perigynia, smooth sheaths, and small, rounded, veined perigynia.
56) C. projecta- Fairly common in wet to mesic forests and shaded wetlands. Normally identifiable by its drooping or arching inflorescences, baggy leaf sheaths, and narrow perigynia.
57) C. cristatella- Common in all kinds of wetlands. Closely related to C. projecta and C. tribuloides, and usually recognizable by the combo of baggy sheaths, wider perigynia, and nearly spherical spikes.
58) C. laevivaginata- Listed as Endangered in Wisconsin. Supposedly rare in sedge meadows and forested seeps but popping up more and more with increased awareness from botanists. Alex spotted this in the perched seep, representing a new population. This species is similar to C. stipata, but with smooth sheaths that are thickened at the summit (vs. corrugated and fragile at the summit) and longer teeth on the perigynia, giving the inflorescence a spikier or bristlier look.
59) C. communis- Common in all kinds of forests, but a bit more northern. This far south, most often found in cooler microclimates and on sandy or rocky soil.
60) C. pedunculata- Common in deciduous and mixed forests but often requiring sheltered and north- or east-facing slopes this far south.
61) C. hirtifolia- Common in rich deciduous forests. The only sedge I know of with hair covering every part of the plant.
Alex left us after we'd wrapped up at Bass Hollow, having seen 61 sedge species in 23 hours - four species better than the final total for June 8th.
It was finally time for the hourlong drive to the last stop of the day. Rob met up with us at Mazomanie Oak Barrens State Natural Area for three final hours of botanizing in oak barrens and (mostly) a floodplain of the Wisconsin River. As established at the first stop of the weekend, floodplains are excellent places for sedge diversity. We finished out the day's list of 57 species and picked up 8 I hadn't seen yet:
62) Carex davisii- Uncommon and very local in mesic woodlands (and occasionally upslope savannas) associated with rivers and large streams. My favorite thing about this species is how the perigynia turn burnt orange later in the season. Mazomanie Oak Barrens SNA has an exceptionally large population of this species.
63) C. trichocarpa- Locally abundant in the floodplains of major rivers and their tributaries as well as Driftless Area sedge meadows.
64) C. grayi- Common in rich forests, especially floodplains.
65) C. typhina- Uncommon in floodplains and slopes associated with rivers and large streams. I see this species much less frequently than range maps suggest.
66) C. muskingumensis- Wet, flat deciduous woods, especially vernal pools and swales within floodplains. A completely distinctive member of section Cyperoideae with narrow spikes and perfectly three-ranked leaves (pointing in only three directions when seen from above).
67) C. echinodes- Uncommon in floodplains and other wet, flat woods. The final addition from section Cyperoideae, similar to Carex tenera but slightly larger overall, without papillae on the sheaths, and with more spreading perigynia.
68) C. conjuncta- Very rare, as far as we know, in rich deciduous woods and floodplains. I found a single plant on a mesic terrace close to the Wisconsin River, representing a new county record and adding a new site to the very small handful from which this species is known in Wisconsin. This species is in the same section as C. stipata and C. laevivaginata, with a soft, sharply triangular culm that abruptly narrows at the base of the inflorescence. It can be distinguished by habitat, much shorter beaks, and tiny purple dots at the summit of the leaf sheaths. It is also similar to C. alopecoidea, which may be found in similar habitats. C. conjuncta is a larger plant overall, has strongly corrugated leaf sheaths, and has perigynia strongly veined on one side (vs. weakly or not veined on both sides). The plant I found was pretty beat up, so the last two photos below are from plants I saw in Cook County, Illinois. This late find certainly finished the day with a bang!
69) C. lupulina- Common in sloughs, vernal pools, and swales within floodplain forests. The last new species for me this weekend, and one of two final species for June 8th, along with C. emoryi.
This idea turned out to be incredibly fun, and I hope it becomes an annual tradition! I think we went about it the right way by selecting a few sites that were rich in different sets of Carex species and hitting them hard. The daily total of 57 and the weekend total of 69 both exceeded expectations, as did the three great finds (Ludwigia alternifolia, Carex laevivaginata, and Carex conjuncta) we made throughout the day. I liked making it into a weekend, which allowed me to be more thorough in the types of habitats I visited. However, I also enjoyed the more limited geographical area on the day of the actual event. I think that a weekend restricted to a particular county or radius (maybe 25 miles?) would be my personal preference if we do this again in the future. This would add more challenge to the task and make selecting a region a more consequential process.
We also wondered what other groups would make for a good plant ID marathon. I think an Asteraceae day or weekend would be lots of fun, and perhaps also a day finding as many tree species as possible. A grass (Poaceae) weekend might mean many hours of huddling around keys, but it would certainly result in a large species list and provide an interesting challenge in timing it to see as many warm season and cool season species as possible. We thought ferns might be spread a bit too thin, but maybe by selecting the right region we could make that idea work. Happy to take other ideas, as well, and feel free to steal this idea for your own region!
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