Carex conoidea (Openfield Sedge)

Plant Info
Also known as: Field Sedge, Prairie Gray Sedge
Family:Cyperaceae (Sedge)
Life cycle:perennial
Habitat:sun; moist, open soil; prairies, sedge meadows, fens, shores
Fruiting season:June - July
Plant height:6 to 30 inches
Wetland Indicator Status:GP: FAC MW: FACW NCNE: FACW
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] Separate staminate (male) and pistillate (female) spikes, with a single staminate spike up to about ¾ inch long at the top of the stem, at the tip of a rough-textured stalk. Below the staminate spike are 1 to 4 cylindric, all-pistillate spikes each up to 1 inch long, occasionally with a few staminate flowers at the tip (androgynous). Lateral spikes are usually widely separated, sometimes congested near the staminate spike.

[photo of scabrous stalk] Lower pistillate spikes are longer stalked than upper spikes, the stalks mostly erect, with minute, stiff hairs that give a rough texture. Pistillate spikes each have a leaf-like bract at the base of the stalk that often over-tops the terminal spike and loosely sheaths the stem.

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

[photo of sheath and ligule] Leaves are basal and alternate, 2.8 to 5 mm wide, erect to floppy, about as long as or shorter than the flowering stem. Stem leaf sheaths loosely wrap the stem and are papery, translucent whitish. The ligule (membrane where the leaf joins the sheath) is as long as or longer than wide. Leaves are hairless but slightly rough along the edges and midvein, M-shaped in cross-section when young.

[photo of basal sheaths] Bases are wrapped in a yellowish to brown sheath that is not fibrous. Stems are slender, 3-sided, hairless but slightly rough along the angles, erect to ascending, and may elongate up to 30 inches at maturity. Not all plants produce flowering stems. Plants typically form dense clumps.

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 have (8)15 to 25 fruits, the perigynia ascending, spirally arranged on the stalk, overlapping but not crowded.

[photo of perigynia, scales and achene] Pistillate scales are egg-shaped, reddish-brown to whitish with a green midrib that usually extends to a rough-textured awn up to 2.7 mm long, the scale body about half as long as the perigynia, with the awn may be longer. Perigynia are green to yellowish-green, 2.5 to 4 mm long, 1.2 to 1.8 mm wide, hairless, shiny, slightly inflated, 17 to 25-veined with impressed veins, oblong-elliptic, bullet-shaped and round in cross-section, tapering at the tip, the beak absent or minute, straight and toothless. Achenes are 1.8 to 2.6 mm long, weakly 3-sided in cross-section, widest above the middle, tapering to a stalk-like base and maturing to brown.


Carex conoidea is an uncommon sedge throughout most of its range, found in open moist prairies and meadows and along shores.

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 conoidea is in the Griseae section; some of its common traits are: clump forming or not, short to long rhizomatous, basal sheaths not fibrous, leaves M-shaped in cross-section when young, the leaf underside with 2 lateral veins more prominent than the midvein, widest leaves 6 mm or less, 3 to 6 spikes, terminal spike all staminate, lateral spikes mostly all pistillate, sometimes with a few staminate flowers at the tip (androgynous), lateral spikes subtended by a long-sheathing leaf-like bract, pistillate scales with a rough-textured awn, perigynia oval-elliptic and hairless with impressed veins (both fresh and dry), achenes 3-sided with 3 stigmas, usually growing in woodlands or open habitats.

Carex conoidea is distinguished from other Carex species by the combination of: clump forming, usually densely so, all-staminate terminal spike, spike stalks rough to the touch, lateral spikes usually all pistillate, usually more than 15 perigynia per spike, pistillate scales with a rough-textured awn, perigynia oblong-elliptic with 17 to 25 impressed veins, the beak straight and very short or absent altogether.

Carex conoidea most closely resembles Carex grisea, which has smooth stalks on lateral spikes, typically fewer than 15 perigynia per spike, 50+ veins on the perigynia, and is found in deciduous woods and floodplain forest rather than open areas. Immature specimens of Carex tetanica may be similar, when the veins might seem impressed, but its veins are raised when dry, the perigynia has a short, bent beak, and it's colony-forming, not clump-forming. Carex katahdinensis, a dwarf version of C. conoidea, was once treated as a separate species but is now considered a synonym, the dwarf characteristics deemed caused by environmental factors.

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More photos

Photos by K. Chayka taken in Anoka and Fillmore counties.


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