Flower:

A single spike at the top of the stem, lance-elliptic in outline, blunt to pointed at the tip, 1 to 4 mm (to ~1/8 inch) long, with 5 to 30 florets spirally arranged, each floret subtended by a single scale. Scales are 1 to 1.4 mm long, blunt at the tip, purplish-brown to dark red-brown with a green to whitish midrib. Florets have 3 stamens and a 3-parted style. The lowest scale in the spike is rounded, wraps 100% of the stem, and lacks a flower. The second lowest scale has a flower.

Leaves and stems:

The 2 leaves are bladeless and reduced to sheaths on the lower stem. The upper sheath is firm, reddish to straw-colored toward the base, green to yellowish to red towards the tip, may be darker reddish around the tip edge, the front rounded to pointed at the tip, and may have an obscure tooth at the apex. Stems are round in cross-section, thread-like, .15 to .3 mm wide. Stems are ascending to erect and form small colonies from slender rhizomes.

Fruit:

Each flower produces a single achene (seed), that persists on the spike after the scale drops off, the achene with a cap-like appendage (tubercle) at the tip that is clearly distinct from the rest of the achene. Scales become spreading in fruit. Achenes are about .6 mm long (excluding tubercle), .5 mm wide, yellow to orange to brown, covered in a fine network pattern across the surface, 3-sided in cross-section, urn-shaped in outline, rounded at the tip end and tapering at the base. Tubercles are brown, pyramidal and usually depressed, to .15 mm long, about twice as wide as long. There is barely a neck/constriction between the tip of the achene and the base of the tubercle. Bristles surrounding the achene are absent.

Notes:

Eleocharis nitida is a boreal species found across Canada but barely reaches into the northern US around the Great Lakes and in New England, and is one of several rare Spikerushes in Minnesota. Habitats noted in the Bell Herbarium records include roadside ditches, gravel pits, edges of wheel ruts in logging roads and ATV trails, creek banks and along bedrock pools, usually in exposed sandy, clayey or gravelly soils. It was first discovered in Minnesota in the 1940s but, according to the DNR, by 1996 only 6 locations were known. It was listed as a Threatened species at that time but downgraded to Special Concern in 2013 after biological surveys located many additional populations in northeast Minnesota. It is currently listed as Endangered in Wisconsin.

E. nitida is distinguished by very slender stems that are round in cross-section, membranous sheaths that persist and are not shredding, purplish to dark reddish floral scales less than 1.5 mm long, yellow-orange achenes less than .7 mm long with a conspicuous network pattern across the surface, achenes persisting on the spike after scales drop off, no bristles, small tubercle depressed and about twice as wide as long. The tiny spike is normally lance-elliptic, blunt at the tip, with purplish to red-brown scales and the second lowest scale has a flower/fruit.

E. nitida resembles Eleocharis elliptica in virtually all respects, including the persisting achenes, but is much smaller; E. ellipitca achenes are about 1 mm long, floral scales 1.7 to 3 mm long and may be notched at the tip, and stems .3 to .8 mm wide. Eleocharis acicularis is similar in its diminutive form and thread-like stems, but is more densely clump-forming, has papery sheaths that are loose around the stem and often shred, floral scales 1.5 to 2.5 mm long, and achenes have rows of ridges with cross-bars rather than a network pattern.