Rhynchospora capitellata (Brownish Beaksedge)

Plant Info
Also known as: Brownish Beakrush
Genus:Rhynchospora
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Habitat:sun; moist to wet sandy or peaty soil; shores, wet meadows, marshes, swales, seeps, fens, bogs
Fruiting season:July - September
Plant height:8 to 40 inches
Wetland Indicator Status:none
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

Flower: Flower shape: indistinct Cluster type: spike

[photo of terminal clusters and bracts] Two to 5 (or more) inverted cone-shaped to hemispheric clusters, one or more at the tip of the stem, the lower lateral clusters more widely separated on the upper half of the stem. Each cluster is on an erect stalk with a leaf-like bract at the base, the bract usually much longer than the attending cluster and over-topping the terminal cluster. The lowest cluster stalk is longest; stalks are sometimes branched. Each cluster has several to many dark brown spikelets (flower clusters).

[photo of lateral cluster] Spikelets are stalkless or nearly so, 3.5 to 5 mm long (less than ¼ inch), lance-elliptic, pointed at the tip, with 2 to 5 perfect flowers (both male and female parts), each subtended by a scale; the lowest scale is often empty. Flowers have 3 stamens and a 2-parted style. Scales are 2.7 to 3 mm long, elliptic, rounded to pointed at the tip, the midrib sometimes extending at the tip.

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

[photo of stem and sheath] Leaves are alternate, erect to ascending, hairless, flat at the base becoming 3-sided near the tip, 1 to 3.5 mm wide, shorter than the flowering stem but the upper leaves usually over-topping the terminal cluster. Sheaths are closed, straight across to convex at the tip, translucent green and membranous on the front. Stems are erect, unbranched, round to weakly 3-sided in cross-section, hairless, green, leafy, and multiple from the base usually forming dense clumps.

Fruit: Fruit type: seed without plume

[close-up of spikelets just past flowering] Spikelets produce 2 to 5 achenes (seeds), 2.5 to 3 mm long, about 1 mm wide, flattened lens-shaped in cross-section, urn-shaped in outline, widest near the tip (obovate), the persistent style forming a narrowly triangular beak up to 1.5 mm long, and tapering at the base to a stalk-like appendage (stipe). Surrounding the base are 6 barbed bristles all about as long as or slightly shorter than the achene, including the beak, and the barbs downward pointing.

Notes:

Rhynchospora capitellata was unknown in Minnesota until 2011, when it was discovered on a lake shore in General CC Andrews State Forest in northern Pine County. The DNR has been tracking it ever since but, to our knowledge, no new populations have yet turned up. Of note is that we visited the Pine County site in 2017, but with water levels exceptionally high several years in a row, that population was all under water and may not have survived.

With its flattish leaves, weakly 3-sided stems and fairly dense terminal clusters it can strongly resemble the related Rhynchospora alba, especially when that species' spikelets turn brown, but R. alba spikelets are usually whitish to light brown, bracts are shorter and achenes have 9 to 12 bristles.

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More photos

Photos by Peter M. Dziuk taken in Wisconsin.

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