Carex eburnea (Ivory Sedge)

Plant Info
Also known as: Bristleleaf Sedge
Genus:Carex
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Habitat:part shade, shade; dry to moist sandy or rocky soil; shady bluffs, conifer or mixed forest, cedar thickets, dunes
Fruiting season:May - July
Plant height:3 to 12 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: Cluster type: spike

[photo of flowering spikes] Separate staminate (male) and pistillate (female) spikes, with a single staminate spike up to 3/8 inch long at the tip of the stem. Below the staminate spike are 2 or 3 pistillate spikes, the upper spike(s) crowding the staminate spike, the lower (when present) some distance below. Spikes are green to whitish at flowering time and essentially stalkless, the staminate spike with creamy yellow stamens, pistillate spikes with white, thread-like styles. At the base of a pistillate stalk is a scale-like bract with a long, tubular sheath. The pistillate spikes become long-stalked as the plant matures, the erect stalks usually overtopping and partly hiding the staminate spike.

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

[photo showing leaf and stem widths] Leaves are basal and alternate, mostly near the base, up to 8 inches long, up to 1mm wide, shorter than the flowering stems, initially erect to ascending and becoming arching. Sheaths are tight and yellowish; ligules are obscure. Leaves are hairless and typically roll up along the edge.

[photo of basal sheaths] Bases are wrapped in a light brown sheath that is not fibrous, with old, dead leaves persisting to the next season. Stems are erect to ascending, slender, weakly 3-sided, and mostly smooth. Often only 3 or 4 inches tall at flowering time, the slender stems elongate up to 12 inches at maturity and remain longer than the leaves. Plants form clumps and can create colonies from slender, light brown rhizomes.

Fruit: Fruit type: capsule/pod

[photo of mature spikes] Fruit develops in late spring to early summer, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. The scales of staminate spikes are oval-elliptic with white edging and a blunt or pointed tip. Each pistillate spike contains 2 to 6 fruits.

[photo of scale, perigynia and achene] Pistillate scales are 1 to 2 mm long, 1.2 to 1.8 mm wide, broadly egg-shaped with a blunt or pointed tip, whitish with a darker green or brown midvein, and may be nearly as long as the perigynia. Perigynia are 1.5 to 2.2 mm long, .7 to 1.1 mm wide, 2-ribbed, turn glossy brown-black at maturity, are generally urn-shaped and not spongy, the body elliptic with a minute, straight beak lacking distinct teeth at the tip. Achenes are 1.3 to 2.3 mm long, .9 to 1.4 mm wide, elliptic, distinctly 3-sided, and mature to dark brown.

Notes:

Carex eburnea is a delicate little sedge primarily found on wooded ridges and bluffs along the Minnesota and Mississippi river valleys, though in other areas it may be found in mixed deciduous/conifer forest, particularly under and near cedars, on calcareous substrates, and occasionally found in fens and on dunes. It does well in a shade garden and tolerates a variety of soil types and moisture conditions.

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 eburnea is the lone member of the Albae section in Minnesota; some of the section's common traits are: clump forming and rhizomatous, leaves mostly less than 1mm wide, basal sheaths not fibrous, 3 to 5 spikes per stem, terminal spike all staminate, pistillate spikes stalked and often overtopping the staminate spike, perigynia hairless and weakly veined but for 2 prominent veins, perigynia abruptly tapering to a short beak, achenes 3-sided to round in cross-section.

Carex eburnea should not be confused with any other sedge in Minnesota; the long-stalked pistillate spikes with few fruits combined with long-sheathing bracts and slender leaves shorter than the stems are unique. The perigynia often do not fall off until fall, some even persisting through winter, the blackish fruits still present when the plant flowers the next spring.

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More photos

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

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