Carex cephalophora (Oval-headed Sedge)

Plant Info
Also known as: Oval-leaf Sedge, Short-headed Bracted Sedge
Genus:Carex
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Habitat:part shade, sun; dry to average moisture; open woods, thickets, wooded slopes, rarely open fields
Fruiting season:June - July
Plant height:8 to 36 inches
Wetland Indicator Status:GP: FACU 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 just past flowering] A dense, oval to short-cylindric cluster up to ¾ inch long at the top of the stem, made up of 3 to 8 round spikes, all tightly crowded with virtually no separation between them. The terminal spike has staminate (male) flowers at the tip and pistillate (female) flowers at the base (androgynous), with the lateral spikes usually also androgynous. At the base of each spike is a bristle-like bract, which may or may not be longer than the attending spike. Bracts are quite variable in length but the lowest bract is usually longest, often over-topping the terminal spike and is sometimes more leaf-like than the other bracts.

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

[photo of sheaths and ligule] Leaves are basal and alternate, mostly near the base, mostly floppy, the largest 2 to 5 mm wide, shorter than to a little longer than the flowering stems, though vegetative shoots may be longer. Stem leaf sheaths tightly wrap the stem and are translucent whitish, concave and slightly thickened at the tip, though sometimes barely so. The ligule (membrane where the leaf joins the sheath) is longer than wide. Leaves are hairless and V-shaped in cross-section when young.

[photo of plant base] The back of the sheath is not strongly green and white striped or mottled. Bases are wrapped in a brown sheath that may become fibrous with age. Stems are erect to ascending though may flop over with age, up to 3.5 mm wide at the base and much more slender above, 3-sided, smooth, elongating up to 36 inches at maturity, up to twice as long as the leaves. Plants are loosely to densely clump-forming and are 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 4 to 20 fruits that are spreading to ascending and tightly crowded on the stalk.

[photo of perigynia, scales and achene] Pistillate scales are egg-shaped to nearly round, translucent white with a green midrib, abruptly pointed at the tip or the midrib extending to an awn (usually short, sometimes long), the scale body not more than half as long as the perigynia and the awn not usually extending beyond the perigynia. Perigynia are 2.5 to 3.5 mm long, 1.4 to 2 mm wide, green to yellowish at maturity, veinless or obscurely 8-veined on the back, hairless but with minute teeth along the edge on the upper half, not much inflated but slightly spongy at the base, flattened on the back side, elliptic to nearly round in outline, widest near the middle, tapering to a toothed beak up to 1.1 mm long. Achenes are 1 to 2 mm long, flattened lens-shaped, egg-shaped to nearly round in outline, and mature to yellow-brown.

Notes:

Carex cephalophora is found primarily in dry, deciduous woods and reaches the northwest tip of its 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 cephalophora 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 cephalophora is distinguished by its woodland habitat, tight sheaths slightly thickened at the tip and not cross-wrinkled, 3 to 8 round spikes all tightly crowded at the tip, bristle-like bracts of varying lengths, spikes with 20 or fewer perigynia that are spreading to ascending, perigynia 2.5 to 3.5mm long, green to yellowish at maturity, and pistillate scales up to half as long as the perigynia, the tip usually extended to an awn (short or long). Most similar are Carex muehlenbergii and Carex gravida, both of which have looser and more fragile sheaths that may be cross-wrinkled on the front, less tightly crowded spikes with at least some visible separation, and pistillate scales are nearly as long as the perigynia and pointed at the tip but not awned.

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More photos

Photos by K. Chayka taken in Fillmore County and in the garden. Photos by Peter M. Dziuk taken in Dakota County. Photo by Daniel L. Nickrent used by permission via PhytoImages.

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