Carex xerantica (Whitescale Sedge)
|Also known as:
|Dry Sedge, Dry-land Sedge
|sun; dry sandy or rocky soil; prairies, bluffs, rock outcrops, dry hillsides, plains
|June - July
|1 to 2 feet
|Wetland Indicator Status:
|MN county distribution (click map to enlarge):
|National distribution (click map to enlarge):
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3 to 6 spikes each 8 to 14 mm (to ~½ inch) long, overlapping but not crowded at the tip of the stem, the inflorescence (group of spikes) erect and up to 2 inches long. All spikes are stalkless, mostly erect and appressed to the stem, elliptic in outline, tapering at both ends, 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 that may have a bristle-like tip.
Leaves and stems:
Leaves are alternate with 2 to 3 leaves near the base, 4 to 8 inches long, 1 to 3 mm wide, flat, hairless, rough-textured near the tip, shorter than the flowering stems. Stem leaf sheaths tightly wrap the stem and are translucent whitish on the front; the membranous tip may extend slightly above the leaf base and is concave to nearly straight across the top edge. The ligule (membrane where the leaf joins the sheath) is about as wide as long. Bases are wrapped in a brown sheath. Stems are hairless, erect to ascending, 3-sided in cross-section, mostly smooth except just below the spikes. Stems may elongate to about 24 inches at maturity and are longer than the leaves. Plants are clump forming and not colony forming.
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 erect and tightly crowded on the spike. Each spike contains numerous fruits.
Pistillate scales are lance-shaped, translucent white to yellowish with a green to gold midrib drying to pale brown, pointed at the tip, as long as and about as wide as the perigynia, completely covering it. Perigynia are 3.8 to 5.6 mm long, 1.5 to 2.3 mm wide, green to golden at maturity, hairless, veinless or faintly veined on both sides (most noticeable when dry), flattened on the back, not inflated, lance-elliptic, tapering at the base, tapering to the beak, and has a wing .2 to .4 mm wide around the edges that does not extend to the base and is commonly obscure until the perigynia dries down. Achenes are lens-shaped, brown at maturity, 1.7 to 2.1 mm long, 1.2 to 1.4 mm wide, narrowly egg-shaped to oblong-elliptic, longer than wide; the distance from the tip of the achene to the tip of the beak is 1.4 to 2.2 mm.
Carex xerantica is an uncommon sedge in Minnesota, with most populations the northwest prairie region of Minnesota, though it's also been found on exposed cliffs in northern Cook County near the Canadian border. According to the DNR, its role in Minnesota's prairies has not been studied in much detail, but suffice to say that the disappearance of native prairie has had an impact on its chances for survival. With fewer than 20 populations known to exist, it was listed as a Special Concern species in 1996.
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 xerantica 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 xerantica is fairly distinctive for an Ovales, characterized by the 3 to 6 spikes that are overlapping but not tightly crowded, elliptic in outline tapering to a point at both ends, mostly erect and appressed to the stem; pistillate scales as long as the perigynia and commonly white, giving the spikes an almost silvery cast; perigynia 3.8 to 5.5 mm long, lance-elliptic to nearly diamond-shaped tapering at both ends, veinless or faintly many-veined on both sides, obscurely winged and minutely serrated along the beak edges. The distance from the tip of the achene to the tip of the beak is 1.4 to 2.2 mm. The whitish pistillate scales completely covering the perigynia, mostly appressed spikes tapering at both ends, and the mostly erect inflorescence are key to an ID. It is also typically found in dry, sandy or gravelly soil.
The pistillate scales as long as the perigynia is a trait shared with other Minnesota Ovales sedges, notably C. adusta, C. praticola, C. foenea and C. tenera. All of these typically have spikes darker brown and more rounded at one or both ends, and all but C. adusta commonly have a nodding, bent or arching inflorescence. Of note is that C. xerantica is described as clump-forming, but where we found it, it was scattered in the area, only one or two stems with no significant basal clump. This could have been due to heavy competition in that particular area, which was a moister spot in an otherwise dry, sandy prairie.
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Photos by K. Chayka and Peter M. Dziuk taken in Clay County.
Have you seen this plant in Minnesota, or have any other comments about it?