Carex duriuscula (Needleleaf Sedge)
|Also known as:||Spike-rush Sedge|
|Habitat:||sun; dry sandy or rocky soil; prairies, rock outcrops, grassy slopes, conifer forests|
|Fruiting season:||May - July|
|Plant height:||2 to 8 inches|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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3 to 8 small spikes, stalkless, erect to ascending, crowded at the tip of the stem or slightly separated from each other, the group of spikes (inflorescence) ¼ to ¾ inch long. Spikes on a stem mostly have staminate (male) flowers at the tip and pistillate (female) flowers below (androgynous). Stamen tips (anthers) are smooth or have a warty protuberance at the top (30x magnification required). At the base of each spike is a sheathless, scale-like bract with a bristle-like tip, usually shorter than the attending spike.
Leaves and stems:
Leaves are basal and alternate with 1 to 4 leaves all near the base of the stem, .6 to 1.5 mm wide, shorter than the flowering stems with leaves on vegetative shoots up to 6 inches long. Stem leaf sheaths tightly wrap the stem, the front translucent whitish, straight to slightly concave across the top and the tip not extended above the leaf base. The ligule (membrane where the leaf joins the sheath) is wider than long. Leaves are hairless but rough along the edges, flat near the base but rolled in along the edges (involute) towards the tip, and erect to spreading.
Bases are wrapped in a brown to gray-brown, bladeless sheath that becomes fibrous, with old sheaths and leaves persisting to the next season. Stems are slender, 3-sided, bluntly angled, smooth, erect, elongating only up to about 8 inches at maturity, single or a few from the base. Plants form clonal colonies from long, slender, scaly brown rhizomes, the shoots arising singly or multiples in a cluster at irregular intervals.
Fruit develops in late spring through summer, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Pistillate spikes usually contain 1 to 8 fruits that are erect to ascending and overlapping on the stalk.
Pistillate scales are lance to egg-shaped, very thin and easily torn, reddish-brown with whitish edging and a green midrib drying to light brown, tapering to a pointed tip, about as wide and long as or slightly longer than the perigynia, concealing it. Perigynia are 2.4 to 3.5 mm long, 1.5 to 2.1 mm wide, dark reddish-brown to blackish-brown at maturity, convex and faintly veined only at the base on the front, flat and veinless on the back and thickened along the edges, tightly wrapping the achene, hairless but with minute serrations along the edges on the tip half, the body egg-shaped to nearly round, tapered to a beak less than 1 mm long with 2 small teeth at the tip. Achenes are 1.5 to 2 mm long, about 1.5 mm wide, dark brown when mature, flattened lens-shaped.
Carex duriuscula, formerly known as Carex eleocharis or C. stenophylla, is an occasional to common sedge of open, dry, sandy or rocky soil, often in prairies and rock outcrops but also sandy river banks and railroad rights-of-way. It reaches the eastern edge of its range in Minnesota and is considered introduced and adventive farther east where it's found mostly along transportation corridors.
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 duriuscula is in the Divisae section; some of its common traits are: not clump-forming, long-rhizomatous, basal sheaths brown to black and fibrous or not, leaves hairless and V-shaped in cross-section when young, bracts scale-like or absent, 3 to 25 spikes often congested at the tip, spikes with staminate flowers at the tip (androgynous) or unisex, perigynia flattened in cross-section, veined on one or both sides, rounded and spongy at the base, beaked with 2 teeth at the tip, flattened lens-shaped achenes.
Carex duriuscula is distinguished from other sedges by the combination of: not clump-forming, colony forming from slender (less than 2mm diameter) rhizomes, fruiting stems only to about 8 inches tall (often less than 6), widest leaves 1.5mm wide or less, 3 to 8 spikes congested at the tip of the stem in a head less than ¾ inch long, spikes mostly with staminate flowers at the tip (androgynous), anther tips warty or smooth, perigynia 2.5 to 3.5mm long, reddish to brownish-black at maturity. Most similar is Carex praegracilis, which has thicker rhizomes (2 to 4mm diameter), widest leaves to 3mm, anther tips minutely hairy, stems more than 12 inches tall, inflorescence ¾ to 2 inches long, and primarily found in moist to wet soils. Also similar is Carex siccata, which has thick rhizomes, much larger perigynia (4 to 6.5mm long) and leaf sheaths that extend above the leaf base.
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Photos by Peter M. Dziuk taken in Laq Qui Parle, Otter Tail and Yellow Medicine counties.
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