Carex scirpoidea (Northern Single-spike Sedge)

Plant Info
Also known as: Canadian Single-spike Sedge, Bulrush Sedge
Genus:Carex
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Status:
  • State Special Concern
Habitat:sun; average to wet; prairies, fens, sedge meadows,
Fruiting season:June - August
Plant height:6 to 27 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] Usually a single erect spike up to 1 inch long at the top of the stem, narrowly elliptic, either all-pistillate (female) or all-staminate (male), the staminate spikes somewhat smaller than the pistillate. Occasionally a small lateral spike of the same sex is just below the terminal spike. At the base of the spike is a scale-like bract.

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

[photo of leaf hairs, sheath and ligule] Leaves are few, alternately attached to the stem near the base, 1 to 2.5 mm wide, shorter than the flowering stems. Leaves are mostly hairless except for sparse hairs on the upper surface near the base. The sheath front is membranous, densely covered in minute hairs, and straight across to concave at the tip. The ligule (membrane where the leaf meets the sheath) is rounded to pointed at the tip and about as long as or slightly longer than wide.

[photo of basal sheaths] Bases are wrapped in a red-brown to purple-brown sheath that is not fibrous. Stems are mostly erect, 3-sided, very slender, elongating up to 27 inches at maturity and remain longer than the leaves. Plants form small to dense clumps from short rhizomes.

Fruit: Fruit type: seed without plume

[close-up of developing perigynia] Fruit develops in early summer, the spike forming a cluster of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. A pistillate spike contains numerous fruits, crowded and appressed to ascending.

[photo of perigynia, scale and achene] Pistillate scales are lance-oval with a blunt to pointed tip, red-brown to purple with whitish edging and a fringe of hairs on the tip half, and are half to about as long as the perigynia. Perigynia are 2 to 2.5 mm long, 1 to 1.2 mm wide, veinless except for 2 ribs, yellow-brown to chestnut colored when mature, tightly wrap the achene, lance-elliptic, tapering at the base, tapering at the tip to an obscure, toothless beak, and covered with long white hairs on the upper half or so. Achenes are 1.5 to 1.8 mm long, .8 to 1.2 mm wide, 3-sided with rounded angles, dark brown when mature.

Notes:

Carex scirpoidea is an uncommon species in Minnesota, found primarily in wet-mesic prairies with calcareous or somewhat saline soils. According to the DNR, its preferred habitat is something of a narrow transition zone between upland and wetland, but either way, most of its prairie habitat in western MN has been either plowed under in favor of row crops or mined for gravel. Only a few fragmented remnants remain, which is incredibly sad. C. scirpoidea was listed as a Special Concern species in 1984.

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 scirpoidea is the lone member of the Scirpinae section in Minnesota; some of the section's common traits are: usually clump forming, basal sheaths red-brown to purple, stem sheaths hairy, leaves V-shaped in cross-section when young and may be minutely hairy, usually a single spike either all-staminate or all-pistillate (rarely with a small lateral spike), perigynia erect, hairy, obscurely veined at best, rounded 3-sided in cross-section, achenes 3-sided.

Carex scirpoidea should not be confused with any other sedge in Minnesota; it is distinguished by the combination of: usually a single all-pistillate or all-staminate spike, rarely a small lateral spike of the same sex; perigynia, pistillate scales, and sheaths all hairy. It superficially resembles Carex hallii, with which it may grow, but which is hairless and usually has small all-pistillate lateral spikes just below the terminal spike.

There are 4 subspecies of C. scirpoidea, only one of which is confirmed in Minnesota. They are distinguished by combinations of: clump-forming habit or not, rhizomes short or long, old leaves and sheaths persisting or not, shape of the perigynia, and leaf width. Subsp. scirpoidea, the most common of the 4, present in Minnesota and described above, is loosely clump-forming, old sheaths do not persist, perigynia is not more than 2.5 times as long as wide, and widest leaves are more than 1.5 mm wide. Subsp. convoluta is only known from the Lake Huron area and is like subsp. scirpoidea except widest leaves are not more than 1.5 mm wide and are folded or nearly so (it's been suggested that the Lake County record might be this subsp. but that is not confirmed). Subsp. pseudoscripoidea and subsp. stenochlaena are both western species, the former not clump-forming and with persistent old leaves, and the latter clump-forming without persistent old leaves and the perigynia more than 2.5 times as long as wide.

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More photos

Photos by K. Chayka and Peter M. Dziuk taken in Marshall County.

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