Carex buxbaumii (Buxbaum's Sedge)

Plant Info
Also known as: Brown Bog Sedge
Family:Cyperaceae (Sedge)
Life cycle:perennial
Habitat:part shade, sun; moist to wet; marshes, fens, wet meadows, shores, wet ditches, prairie swales
Fruiting season:June - July
Plant height:10 to 30 inches
Wetland Indicator Status:GP: OBL MW: OBL NCNE: OBL
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] 3 to 5 spikes, erect to ascending, mostly short-stalked, each 3/8 to 1 inch long, oval to cylindric in outline, all near the tip but not crowded together. The terminal spike is typically staminate (male) at the base and pistillate (female) at the tip (gynecandrous), but may have a few staminate flowers at the very tip as well as the base (androgynecandrous); lateral spikes are all-pistillate. At the base of each pistillate spike is a bract that may or may not over-top the terminal spike. The bract of the lowest spike is largest and leaf-like, with bracts becoming smaller as they ascend the stem, the uppermost bract reduced to a scale or bristle. At flowering time the spikes are dark purplish-brown, the pistillate flowers with white, thread-like styles, the staminate flowers with creamy yellow stamens.

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

[photo of sheath and ligule] Leaves are basal and alternate, mostly near the base, 2 to 3.5 mm wide, shorter than the flowering stems. Stem leaf sheaths tightly wrap the stem, are membranous on the front side, concave to U-shaped at the tip, typically red-dotted or streaked and may shred, forming a ladder pattern across the front. The ligule (membrane where the leaf joins the sheath) is much longer than wide with sharp point at the tip and a band of loose tissue around the edge. Leaves are hairless but rough along the edges, often with a waxy coating especially on the underside, V-shaped when young and becoming flat.

[photo of basal sheaths] Bases are wrapped in a sheath that is reddish-brown to purplish at the base and fibrous, often forming ladder patterns (ladder-fibrillose) across the front. Stems are mostly erect, 3-sided, smooth except near the spikes, elongating up to about 30 inches at maturity, and are longer than the leaves. Stems arise singly or a few together from long, creeping rhizomes, often forming large stands.

Fruit: Fruit type: seed without plume

[close up of maturing terminal spike] Fruit develops in late spring through mid-summer, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Staminate scales are large and showy, narrowly triangular, dark purplish-brown with a green midrib. Pistillate spikes each contain up to 40 fruits that are ascending to spreading and crowded on the spike.

[photo of perigynia, scale and achene] Pistillate scales are lance to egg-shaped, dark purplish-brown with a green midrib, a short or long taper to a sharply pointed tip or the midrib extending to a long awn, the scale body shorter than to nearly as long as the perigynia and the awn usually extending beyond it, and are conspicuous against the lighter colored perigynia. Perigynia are 2.5 to 4 mm long, hairless, light green to gray-green turning brownish at maturity, faintly veined, not much inflated except at the tip end, oval-elliptic in outline and somewhat flattened, widest at or below the middle, beakless or with a minute beak, the tip with or without 2 small teeth. Achenes are 1.4 to 2.1 mm long, 1.1 to 1.5 mm wide, 3-sided in cross-section, widest near the tip, nearly as wide as the perigynia but rather shorter.


Carex buxbaumii is a common sedge of fens, sedge meadows and other wet places, often in peaty soils and often forming large stands. It is less abundant on the rocky shore of Lake Superior where it may be found on the margins of rock pools.

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 media is in the Racemosae (formerly Atratae) section; some of its common traits are: loosely to densely clump forming, sometimes rhizomatous, base usually red-purple and often fibrous, leaves hairless and V-shaped in cross-section when young, 1 to 10 spikes, the lowest bract leaf-like or thread-like, spikes round to cylindric in outline, terminal spike usually pistillate at the tip and staminate at the base (gynecandrous), lateral spikes all-pistillate or with a few staminate flowers at the base, pistillate scales dark brown to black and blunt-tipped to awned, perigynia erect to spreading, hairless, somewhat flattened, short-beaked to beakless, the beak sometimes toothed, 3-sided achenes, usually calcareous habitats.

Carex buxbaumii should not be confused with any other sedge in Minnesota; it is distinguished by the combination of: rhizomatous, bases reddish-purple and fibrous, 3 to 5 spikes, terminal spike pistillate at the tip and staminate at the base (gynecandrous) or sometimes with a few staminate flowers also at the tip (androgynecandrous), lateral spikes all-pistillate, erect to ascending, short-stalked and not crowded together, pistillate scales dark purplish-brown with a green midrib, scales usually longer than the perigynia, perigynia slightly flattened, light green to gray-green, beakless or minutely beaked.

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More photos

Photos by K. Chayka taken at Blaine Preserve SNA, Anoka County, and in her backyard garden in Ramsey County. Photos courtesy Peter M. Dziuk taken in Anoka, Cook, and Kittson counties.


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