Carex laxiculmis (Spreading Sedge)

Plant Info
Also known as: Creeping Sedge, Loose-culmed Sedge
Genus:Carex
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Status:
  • State Threatened
Habitat:part shade, shade; moist; rich woods, stream banks, ravines, wooded bluffs
Fruiting season:June - July
Plant height:6 to 24 inches
Wetland Indicator Status:none
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Spikes: Flower shape: indistinct Cluster type: spike

[photo of spike clusters] Separate staminate (male) and pistillate (female) spikes, with a single staminate spike up to about ¾ inch long at the top of the stem. Below the staminate spike are 2 to 4 widely spaced, narrowly cylindric, pistillate spikes each up to about ¾ inch long, usually with 1 or 2 staminate flowers at the base (gynecandrous). The upper spikes are erect on short, stiff stalks, the lower spikes drooping on slender stalks up to 4 inches long, with the lowest spike near the base. Pistillate spikes each have a leaf-like bract at the base of the stalk that is usually longer than the spike and may overtop the terminal spike.

Leaves and stems: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of leaves] Leaves are basal and alternate on the lower stem, up to 12 inches long, 4 to 12 mm (to ½ inch) wide, mostly floppy, rough along the edges, and mostly shorter than the flowering stem. Stem leaf sheaths are papery, translucent whitish, often at least partly brown-tinged and red-dotted. The ligule (membrane where the leaf joins the sheath) is longer than wide. Leaves are hairless, green to blue-green, M-shaped in cross-section, with a prominent midrib and 2 conspicuous lateral veins.

[photo of basal sheaths] Bases are wrapped in a whitish or cinnamon-brown sheath that is not fibrous. Stems are 3-sided, smooth or nearly so, weak and often sprawling, and may elongate up to 24 inches at maturity. Plants form dense clumps from a mix of flowering and vegetative stems.

Fruit: Fruit type: seed_without_plume

[close-up of maturing spike] Fruit develops in spring to early summer, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Staminate scales are brown to whitish with a prominent green midrib and mostly pointed at the tip. Pistillate spikes have 4 to 10 fruits, the perigynia erect to ascending, overlapping but often loosely so and alternately arranged on the spike.

[photo of developing perigynia, scales and achene] Pistillate scales are 2.5 to 3.2 mm long, usually whitish with a prominent green midrib, tapering to a pointed tip, sometimes the midrib extending to an awn up to 1 mm long, the scale body nearly as long as the perigynia but angled to appear shorter. Perigynia are green at maturity, 2.5 to 4 mm long, 1.5 to 2 mm wide, many-veined, hairless, not much inflated, strongly 3-sided, oval-elliptic tapering at both ends, slightly bent at the tip with a short, toothless beak. Achenes are 2.2 to 3.2 mm long, essentially filling the perigynia, strongly 3-sided in cross-section with concave sides, broadly oval in outline, broadest at or above the middle, yellowish-brown at maturity.

Notes:

Carex laxiculmis is a sedge of rich deciduous woods, wooded slopes and ravines, and reaches the northwest edge of its range in southeast Minnesota. The first record was from Beaver Creek Valley in Houston County in 1977. According to the DNR, it was listed as a Special Concern species in 1984 and elevated to Threatened in 1996 after biological surveys determined it was more rare than previously thought. Its rich, deciduous forest habitat has been fragmented and degraded from incompatible agricultural and urban uses.

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 laxiculmis is in the Careyanae section; some of its common traits are: clump forming, short rhizomatous, basal sheaths brown or red-purple and not fibrous, leaves M-shaped in cross-section when young, leaves hairless and often over 1 cm (~3/8 inch) wide, 2 to 6 spikes, terminal spike all staminate, lateral spikes all pistillate, lateral spikes subtended by a long-sheathing leaf-like (sometimes bladeless) bract, the lowest spike often at or near the base, perigynia hairless, oval-elliptic to egg-shaped with a toothless beak, distinctly many veined, achenes strongly 3-sided with 3 stigmas, usually growing in woodlands. Members of Careyanae were formerly in Laxiflorae, which is distinguished by perigynia that are round to weakly 3-sided in cross-section, and no pistillate spikes at or near the base.

Carex laxiculmis is distinguished from other Carex species by the combination of: densely clump-forming, leaves up to 12 mm wide and M-shaped in cross-section, basal sheaths whitish to cinnamon-brown, leaf-like bracts that may overtop the terminal spike, terminal spike all staminate, lateral 2 to 4 spikes pistillate but often with 1 or 2 staminate flowers at the base, the lowest pistillate spike near the base on a slender drooping stalk, uppermost pistillate spikes on short, erect stalks, perigynia strongly 3-sided and many-veined, achenes strongly 3-sided with concave sides. Some references note the perigynia is minutely stiff-hairy (hispidulous) but any hairs are not visible to the naked eye. The strongly 3-sided perigynia plus the 1 or 2 staminate scales at the base of pistillate spikes should distinguish it from other similar species.

There are 2 recognized varieties of C. laxiculmis: var. laxiculmis, present just to our south and east (including Iowa and Wisconsin) and as far east as New England, has blue-green (glaucous) foliage and widest leaves up to 12 mm; var. copulata, present in the midwest (including Minnesota) and as far east as Virginia and North Carolina, has green foliage and widest leaves to 8.5 mm.

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More photos

Photos by K. Chayka taken in Winona County. Photos by Peter M. Dziuk taken in Fillmore, Houston and Winona counties.

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