Scleria verticillata (Whorled Nutrush)
|Also known as:||Low Nutrush, Low Nutsedge|
|Habitat:||sun; wet; calcareous fens, sandy or marly shores|
|Fruiting season:||July - September|
|Plant height:||4 to 24 inches|
|Wetland Indicator Status:||GP: OBL MW: OBL NCNE: OBL|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Inverted cone-shaped to hemispheric clusters, one at the stem tip and 1 to 8 lateral clusters, widely spaced, stalkless to short-stalked, each 3 to 7 mm (to ~¼ inch) across. At the base of each cluster is a scale-like bract with a midrib that extends to a bristle-like tip, the lowest bract largest, somewhat longer than the associated cluster but not over-topping the terminal cluster. Each cluster has 5 to 12 spikelets (flower clusters) of one to a few flowers each, usually a mix of staminate (male) and pistillate (female) flowers, sometimes a single sex.
Spikelets are erect to ascending, 2 to 3 mm long (to ~1/8 inch). Each flower is subtended by a scale; the lowest scales in a spikelet are often empty. Staminate flowers have 1 to 3 stamens, pistillate flowers have a 2 or 3-parted style on a round, warty ovary. Scales are red or purple-spotted to brown with a prominent green midrib, lance-shaped tapering to a pointed tip or the midrib extending to a short awn.
Leaves and stems:
Leaves are alternate, erect to ascending, hairless, linear to thread-like, .5 to 2 mm wide, shorter than the flowering stem though the uppermost leaf may over-top the terminal cluster. Leaf sheaths are closed, green or streaked with purple, sparsely long-hairy. Stems are very slender, erect, unbranched, 3-sided in cross-section, hairless, and single or multiple from the base, forming clumps or not.
Pistillate flowers produce a single achene (seed), 1 to 1.5 mm long and about as wide, weakly 3-sided to round in cross-section, the surface warty or covered in short ridges, grayish-brown to white when mature. Attached to the base is short structure called a hypogynium that is gray-brown to white.
Scleria verticillata is a rare sedge of calcareous fens and reaches the northwest edge of its range in Minnesota. According to the DNR, this fen habitat, where S. verticillata and many other rare species are found, is rare and fragile in itself, vulnerable especially to changes in hydrology, which may originate from miles away. Minnesota once held thousands of acres of calcareous fens but only about 2400 acres remain (0.000006% of total wetland acreage), the rest destroyed by development, agriculture, and commercial ventures such as gravel mining. Rare habitat creates rare plants; S. verticillata was listed as a Threatened species in 1984 and is currently a Special Concern species in Wisconsin. At a casual glance it is similar to Rhynchospora species, which have perfect flowers rather than unisex, and much longer, elliptic achenes surrounded by long bristles. The fen habitat, diminutive form, hairy sheaths, and warty, gray to white achenes distinguish Scleria verticillata from other sedges.
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- Scleria verticillata plants
- Scleria verticillata plants
- Scleria verticillata with Pale-spike Lobelia
- a sense of scale
- spikelets with white achenes
- uppermost leaf overtopping the terminal cluster
Photos by Peter M. Dziuk taken in Mahnomen County. Other photos courtesy Steve Eggers.
Have you seen this plant in Minnesota, or have any other comments about it?