Carex gravida (Heavy Sedge)

Plant Info
Also known as: Heavy-fruited Sedge, Long-awned Bracted Sedge
Genus:Carex
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Habitat:sun; average to dry; prairies, ditches, open woods, rock outcrops
Fruiting season:June - July
Plant height:12 to 40 inches
Wetland Indicator Status:GP: FACW MW: FACU NCNE: FACU
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 spikes] A cluster up to 2 inches long at the top of the stem, made up of 5 to 15 round to oval spikes, all crowded at the tip, though the lowest spike may be more separated but not by more than 1½ 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 lateral spikes usually androgynous though some may be all pistillate. At the base of each spike is a narrow, leaf-like bract up to about 1 inch long that does not usually overtop the terminal spike.

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 half of the stem, the largest 3 to 8 mm wide, shorter than to about as long as the flowering stems. Stem leaf sheaths loosely wrap the stem and are translucent whitish, slightly thickened at the tip, fragile and easily torn, sometimes weakly cross-wrinkled (rugose) and/or red-dotted. The ligule (membrane where the leaf joins the sheath) may be shorter or longer than wide. Leaves are hairless and V-shaped in cross-section when young.

[photo of sheath back and basal sheaths] The back of the sheath is longitudinally green and white striped with green cross-veins. Bases are wrapped in a brown sheath that may become fibrous with age. Stems are erect to ascending, up to 8 mm wide at the base and much more slender above, 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 spike] 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 5 to 15 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 turning brown, with a green midrib, tapering to a pointed tip, sometimes the midrib extending to a short awn, and are slightly shorter to slightly longer than the perigynia. Perigynia are 3.5 to 5.5 mm long, 2 to 3 mm wide, green turning yellowish brown at maturity, veinless or obscurely 3 to 7-veined, hairless but with minute teeth along the edge on the upper half, thickened and spongy at the base, flattened on the back side, generally lance-shaped in outline, widest at or below the middle tapering 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 gravida is a common sedge found in open, sunny prairies, outcrops, bluffs, ditches, forest openings, and railroad rights-of-way.

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 gravida 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 gravida is distinguished by its somewhat loose sheaths that are slightly thickened at the tip, not cross-wrinkled on the front or barely so and green and white striped on the back, 5 to 15 round to oval spikes, all near the tip, the lowest separated by not more 1½ times the length of the spike, spikes with 15 or fewer perigynia that are spreading to ascending, flattened on the back side, 3.5 to 5.5mm long, thickened and spongy at the base, and yellowish brown at maturity. Most similar are Carex cephalophora and Carex cephaloidea, both of which are more often found in deciduous woods and have pistillate scales not more than about half as long as the perigynia, and Carex muehlenbergii, which is usually found in open, sandy soil, and has perigynia more oval in outline and distinctly 9 to 15-veined on the front. C. cephalophora has more tightly crowded spikes without any visible separation, sheaths that are tight, and perigynia only 2.5 to 3.2mm long. C. cephaloidea has sheaths that are consistently cross-wrinkled, and bracts are often absent. Some references note 2 varieties of Carex gravida, but these are not recognized in Minnesota.

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More photos

Photos by K. Chayka taken at Louisville Swamp, Scott County. Photos courtesy Peter M. Dziuk taken at Beaver Creek WMA, Fillmore County.

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