Carex bicknellii (Bicknell's Sedge)
|Also known as:||Copper-shouldered Oval Sedge|
|Habitat:||sun; moist to dry sandy soil; prairies, rock outcrops, along railroads, sand barrens, open woods|
|Fruiting season:||June - July|
|Plant height:||1 to 4 feet|
|Wetland Indicator Status:||GP: FACW MW: FACU NCNE: FAC|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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3 to 7 spikes each 10 to 18 mm (3/8 to nearly ¾ inch) long, overlapping at the tip of the stem but not usually crowded, the inflorescence (group of spikes) erect or slightly nodding and 1 to 2+ inches long. All spikes are stalkless, erect to ascending, rounded at the tip, often tapering at the base, oval to club-shaped in outline, with staminate (male) flowers at the base and pistillate (female) flowers at the tip (gynecandrous). At the base of the lowest spike is a scale-like bract with a bristle-like tip that may be longer than the spike but does not overtop the terminal spike.
Leaves and stems:
Leaves are alternate with 3 to 6 leaves on the lower third of the stem, 2.5 to 4.5 mm wide, shorter than the flowering stem, flat, hairless, rough along the edges especially near the tip. Stem leaf sheaths tightly wrap the stem and are mostly green nearly to the tip, the translucent, whitish tip extending up to 2.5 mm above the leaf base and is straight to concave across the top edge. Sheaths are covered in minute bumps (papillose) at least near the tip. The ligule (membrane where the leaf joins the sheath) is about as long as wide. Bases are wrapped in a brown sheath that may be somewhat fibrous, with old leaves often persisting to the next season. Stems are hairless, mostly erect, 3-sided in cross-section, mostly smooth except just below the spikes. Stems elongate to 40+ inches at maturity and are longer than the leaves. Not all plants produce flowering stems and vegetative shoots may be leafier than flowering shoots. Plants are loosely clump forming with fewer than 25 stems in a clump.
Fruit develops in late spring to mid summer, the spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Perigynia are ascending to somewhat spreading and tightly crowded on the spike. Each spike contains 15 to 80 fruits.
Pistillate scales are lance to egg-shaped, reddish-brown with a green midrib drying to brown, blunt to pointed at the tip, 3.1 to 5.4 mm long, 2 to 3 times long as wide, 1.4 to 2.3 mm shorter than the perigynia. Perigynia are 4.5 to 6.7 mm long, 2.8 to 4.2 mm wide, translucent pale brown at maturity, hairless, distinctly 8 to 12-veined on the front and 4 to 8 veined on the back, flattened, not inflated, the body oval to round, round at the base, tapering to a toothed beak 1 to 1.5 mm long at the tip, and has a translucent, papery wing .8 to 1.2 mm wide around the edges that tapers at the base, is often coppery colored and may be somewhat jagged on the upper half. Achenes are lens-shaped, brown, 1.6 to 2.2 mm long, 1.1 to 1.6 mm wide, oblong-elliptic, and are typically visible through the translucent perigynia; the distance from the tip of the achene to the tip of the beak is 2.4 to 3.7 mm.
Carex bicknellii is most common in the southern half of the state, where it may be found in open sandy or rocky soils in mesic prairies, rock outcrops, grassy slopes and occasionally open woods.
Carex is a large genus, with over 600 species in North America and 150+ in Minnesota alone. They are grouped into sections, the species in each group having common traits. Carex bicknellii is a member of the Ovales section, a notoriously difficult group. Some common traits are: usually clump forming, basal sheaths brown and somewhat fibrous, leaves V-shaped when young; 2 to 20 stalkless spikes all at the stem tip and crowded or not, spikes usually all pistillate at the tip and staminate at the base (gynecandrous), lowest bracts scale-like usually with a bristle tip, pistillate scales blunt to pointed at the tip and sometimes awned; perigynia erect to spreading, hairless, veinless to conspicuously veined on one or both surfaces, flat, beaked, usually with a translucent, papery wing; achenes lens-shaped.
Some traits to look at in Ovales are whether spikes are all crowded at the tip or more loosely arranged, whether the inflorescence is nodding or mostly erect, the shape of the spike (round vs. elliptic vs. club-shaped), the size and shape of the perigynia particularly the body (e.g. round vs. elliptic), the width of the wing and whether it extends all the way to the base, whether there are distinct veins on one or both sides of the perigynia, the length of the pistillate scale relative to the perigynia, the shape of the achene, leaf width, and whether sheaths are papillose, but strong magnification (30x or more) is required to see this. Habitat can also be a factor, and a metric scale is essential since fractions of millimeters make a difference.
Carex bicknellii has some of the largest perigynia of the Minnesota Ovales sedges, about 5 mm long or more, the body broadly oval to round with an irregular wing, the upper half or so often tinged golden or coppery brown and commonly has a somewhat ragged edge on one or both sides. The perigynia body is strongly veined on both sides, thin and at least partly translucent so the brown achene is visible through it. The spikes are often club or ice cream cone shaped with a more or less even taper to the base of the staminate portion, though spikes with a shorter staminate portion will be more oval in outline. Sheaths are papillose at least near the tip.
Carex bicknellii is most similar to C. brevior, C. merritt-fernaldii, C. molesta and C. festucacea, all of which have somewhat to significantly smaller perigynia that are strongly veined only on one side and veinless or faintly veined on the other. C. merritt-fernaldii is most similar, with the ragged wing on the perigynia, papillose sheaths, and thinnish perigynia, but its pistillate scales are proportionately longer, usually not more than 1.3 mm shorter than the perigynia where C. bicknellii scales are usually more than 1.3 mm shorter. Their distribution ranges in the state do not really overlap, with C. merritt-fernaldii in north-central and northeast MN and C. bicknellii south and west of that.
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- Carex bicknellii plant
- Carex bicknellii plant
- Carex bicknellii open prairie habitat
- Carex bicknellii rock outcrop habitat
- Carex bicknellii in cultivation
- prominent veins on both sides of perigynia best seen when dry
- spikes are sometimes more oval than club-shaped
- maturing spikes
- comparison of C. bicknellii, C. brevior, C. merritt-fernaldii and C. molesta perigynia
Photos by K. Chayka taken in Pope and Renville counties. Photos by Peter M. Dziuk taken in Brown, Lac Qui Parle, Pope and Renville counties.
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