Carex muehlenbergii (Muhlenberg's Sedge)

Plant Info
Also known as: Sand Sedge
Genus:Carex
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Habitat:sun; dry sandy soil; prairies, dunes, barrens, railroads, forest clearings and edges
Fruiting season:June - July
Plant height:8 to 36 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

Flower: Flower shape: indistinct Cluster type: spike

[photo of flowering spikes] A cluster ½ to 1½ inches long at the top of the stem, made up of 3 to 10 round to oval spikes, the uppermost crowded at the tip, the lower spikes slightly more separated but not by more than 1 times the length of the lowest spike. The terminal spike has staminate (male) flowers at the tip and pistillate (female) flowers at the base (androgynous) with the lateral spikes usually androgynous though some may be all pistillate. At the base of the lowest spike is a narrow, leaf-like bract up to about 1 inch long that does not overtop the terminal spike, with bracts becoming shorter and more bristle-like as the ascend the stem, though most are hidden or obscure.

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

[photo of sheath and ligule] Leaves are basal and alternate along the lower the stem, the largest 2 to 4 mm wide, shorter than the flowering stems. Stem leaf sheaths tightly to somewhat loosely wrap the stem and are translucent whitish, slightly thickened at the tip, cross-wrinkled (rugose) to smooth on the front and sometimes white-dotted. The ligule (membrane where the leaf joins the sheath) is about as wide as or wider than long. Leaves are hairless and V-shaped in cross-section when young.

[photo of base] Bases are wrapped in a brown sheath that may become fibrous with age. Stems are erect to ascending, slender, 3-sided, rough textured on the upper stem, elongating up to about 3 feet at maturity. Plants are clump-forming and not colony-forming.

Fruit: Fruit type: seed without plume

[close-up of maturing spikes] Fruit develops in late spring through early summer, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Pistillate spikes each contain 8 to 20 fruits that are spreading to ascending and crowded on the stalk.

[photo of perigynia front and back, scale and achene] Pistillate scales are egg-shaped, translucent white with a green midrib turning brown, tapering to a pointed tip, sometimes the midrib extending to a short awn, and are 2/3 to about as long as the perigynia. Perigynia are 2.7 to 4.2 mm long, 1.8 to 2.6(3) mm wide, green to yellowish brown at maturity, 9 to 15-veined on the front, veinless or 5 to 9-veined on the back, hairless but with minute teeth along the edge on the upper half, spongy at the base, flattened on the back side, the body oval, abruptly tapered to a toothed beak less than half as long as the perigynia body. Achenes are 1.8 to 2.1 mm long, up to 2 mm wide, flattened lens-shaped, nearly round in outline, and mature to brown.

Notes:

Carex muehlenbergii is an occasional sedge found in open, dry, sandy soils, typically where competition is reduced, and reaches the northwest tip of its US range in Minnesota.

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 muehlenbergii is in the Phaestoglochin section; some of its common traits are: clump forming, basal sheaths usually fibrous, sheath fronts cross-wrinkled (rugose), leaves hairless and V-shaped in cross-section when young, 3 to 15 stalkless spikes (rarely the lower are branched), terminal spike with staminate flowers at the tip (androgynous), lateral spikes androgynous or all pistillate, perigynia ascending to spreading and flattened on the back side, rounded and spongy at the base, beaked, the beak usually toothed, flattened lens-shaped achenes.

Carex muehlenbergii is distinguished by its dry sandy habitat, tight to somewhat loose sheaths that are slightly thickened at the tip and cross-wrinkled to nearly smooth on the front, 3 to 10 round to oval spikes, all near the tip, the lowest separated by not more than 1 times the length of the spike, spikes with 20 or fewer perigynia that are spreading to ascending, flattened on the back side, usually distinctly 9 to 15-veined on the front, 2.7 to 4.2mm long, spongy at the base, yellowish brown at maturity, and pistillate scales 2/3 to as long as the perigynia. Most similar are Carex cephalophora, Carex cephaloidea, and Carex gravida, all of which have veinless perigynia. C. cephalophora and C. cephaloidea also have pistillate scales not more than about half as long as the perigynia and are most often found in deciduous woods, and C. gravida perigynia are somewhat larger, up to 5.5mm, more egg-shaped and thickened at the base. There are 2 varieties of Carex muehlenbergii noted as being present in Minnesota: var. muehlenbergii with pistillate scales 2.5mm or more long, perigynia 3mm or more long and veinless or 5 to 9-veined on the back, and var. enervis with pistillate scales 2.5mm or less long, perigynia 3.1mm or less long and veinless on the back. There are currently no records identified as var. enervis in the Bell Herbarium so its distribution in the state is unknown.

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More photos

Photos by K. Chayka taken in Anoka and Ramsey counties. Photos courtesy Peter M. Dziuk taken in Ramsey County.

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