Carex michauxiana (Michaux's Sedge)

Plant Info
Also known as:
Genus:Carex
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Status:
  • State Special Concern
Habitat:part shade, sun; wet, peaty soil; peatlands, fens, bogs, shores, wet ditches, wet meadows
Fruiting season:June - September
Plant height:6 to 28 inches
Wetland Indicator Status:GP: none MW: none 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: round Cluster type: spike

[photo of flowering spikes] Separate staminate (male) and pistillate (female) spikes, with a single staminate spike ¼ to ½ inch long at the tip of the stem. Below the staminate spike are 2 to 4 erect all-pistillate spikes, nearly round to short cylindric in outline, the uppermost stalkless or short-stalked, crowding the staminate spike and often rising above it, making it inconspicuous. The lowest spike is sometimes some distance farther down the stem, longer stalked, erect to ascending. At the base of each pistillate spike is a leaf-like bract that over-tops the terminal spike, the bract with a long sheath that is concave at the tip.

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

[photo of sheath (should be concave but is torn) and ligule] Leaves are basal and alternate, mostly near the base, 1.5 to 3.5(4.2) mm wide, shorter than the flowering stem. Stem leaf sheaths are concave at the tip, papery translucent whitish-green, and loosely wrap the stem. The ligule (membrane where the leaf joins the sheath) is mostly wider than long. Leaves are M-shaped in cross section when young, yellowish-green, hairless and smooth but may have minute bumps across the upper surface, especially near the tip.

[photo of basal sheaths] Bases are wrapped in a sheath that is green to yellowish-brown and not fibrous. Stems are slender, smooth, erect to ascending, weakly 3-sided in cross-section. Stems elongate up to 28 inches at maturity and are longer than the leaves. Not all plants produce flowering stems. Plants are loosely clump forming and may form mats.

Fruit: Fruit type: seed without plume

[close up of maturing spike] Fruit develops in early to mid-summer, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Perigynia are ascending to widely spreading, the lowest sometimes angled down (reflexed), and are tightly crowded on the spike. Each pistillate spike contains up to 20 fruits.

[photo of perigynia, scale and achene] Pistillate scales are narrowly egg-shaped, whitish turning light brown, a green midrib, pointed at the tip, lack awns, and about half as long as the perigynia. Perigynia are 8.7 to 12.1 mm long, 1.3 to 2.1 mm wide, yellowish at maturity, hairless, 20 to 26-veined, slightly inflated, awl-shaped with a long taper to a straight beak that has scattered minute serrations along the edges and 2 teeth at the tip. Achenes are 3-sided, 2.2 to 3 mm long, 1.2 to 1.7 mm wide, widest at or above the middle, with a long, persistent style.

Notes:

Carex michauxiana reaches the southwestern limit of its range in Minnesota. According to the DNR, it was listed as a Special Concern species in 1996 due to its preference for particular hydrology, pH and mineral concentrations, its peatland habitat also at risk from peat mining as well as climate change. Prior to the 1980s it had only been recorded twice in the state, in wet ditches near Schroeder, Cook County, in the 1940s. Biological surveys over the past few decades have located a number of additional sites in the Arrowhead region. Carex michauxiana is listed as Threatened in Wisconsin.

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 michauxiana is the lone member of the Rostrales section in Minnesota; some of its common traits are: loosely clump forming, hairless leaves, basal sheaths brown to yellowish, 2 to 6 spikes, terminal spike all-staminate, lateral spikes erect to ascending, round to short cylindrical, all-pistillate or with a few staminate flowers at the tip (androgynous), leaf-like bract with a long sheath subtending the lowest pistillate spike, perigynia ascending to spreading, hairless, strongly veined, only slightly inflated, awl-shaped with a long taper to a toothed beaked, achenes 3-sided in cross-section with a long, persistent style.

Carex michauxiana is distinguished from all other Minnesota sedges by the combination of: yellowish-green foliage, slender awl-shaped perigynia up to 12.1 mm long, yellowish when mature, in roundish clusters, the uppermost spikes often hiding the relatively small staminate spike. While it should not be confused for any other Carex in Minnesota, another member of Rostrales—the related Carex folliculata—is present in Wisconsin; it is a much larger plant with leaves up to 21 mm wide. C. michauxiana superficially resembles members of the Lupulinae section, which have broadly inflated periginia, no serrations on the perigynia beak, and red basal sheaths, where C. michauxiana has more slender perigynia and no hint of red or purple on its basal sheaths.

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More photos

Photos courtesy Peter M. Dziuk taken in Lake County.

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