This perennial plant consists of an unbranched culm about 2-6" long
that terminates in a single spikelet. The filiform culm is 0.1-0.4 mm.
across, bright green, and glabrous. At the base of the culm, there is a
truncate sheath that is reddish brown to light tan. There are no leaf
blades along the culm. The terminal spikelet is 2-6 mm. in length,
reddish brown to light tan, lanceoloid to oblongoid-ellipsoid, and
compressed. The spikelet has 5-15 scales that are arranged in two
overlapping ranks. The upper scales have florets, while the lower
scales are sterile. Individual scales are 2.0-2.5 mm. in length,
lanceolate-elliptic, and folded along their central veins. Each scale
has a green central vein, 2 brown lateral veins, and membranous
margins. Each floret is perfect, consisting of an ovary with a
tripartite style and 3 anthers.
The blooming period can occur from
mid-summer into the fall, lasting about 2 weeks for a colony of plants.
The florets are
cross-pollinated by wind. Each fertile floret is replaced by a tiny
achene that is about 0.6-0.8 mm. in length and 0.2-0.4 mm. across at
maturity; the body of this achene is light brown and
oblanceoloid to obovoid in shape with 9-15 longitudinal ribs (requires
10x hand lens to see). At the apex of the achene body, there is a
conical tubercle with a slightly swollen base that is green or white.
The base of this tubercle is more narrow than the apex of the achene
body. From the base of each achene, there originates 0-4 fine bristles
that are a little shorter than the achene. These bristles break off
easily and they are sometimes absent. The achenes are small enough to
about by the wind or they can be carried by currents of water. The root
system is fibrous and rhizomatous. Dense colonies of plants with a
mat-like appearance are often produced from the rhizomes. The culms of
these colonial plants
are initially erect,
but they may later lean in
The preference is full sun,
wet conditions, and soil containing silt, sand, or mud. This spikerush
can adapt to wet ground or shallow water. There is also a form of this
spikerush that is fully aquatic (f.
); this latter form is
sterile. Non-alkaline water pH is preferred. Most growth and
development occurs during the warmer summer months.
The native Needle Spikerush is
common in NE Illinois and occasional in other areas of the state. This
applies to the typical
terrestrial form of the plant. The aquatic form of this plant (f.
) has been observed only in McHenry
County. In addition to
North America, Needle Spikerush also occurs in Eurasia. Habitats
consist of marshes, sedge meadows, calcareous seeps, borders of ponds,
and clear shallow water of ponds. Sometimes the aquatic form of this
plant is cultivated in terrariums.
Several species of leaf beetles and
leafhoppers are known
to feed on Eleocharis
(spikerushes). These species include the
following leaf beetles: Plateumaris
Similarly, the following leafhoppers feed on these
, and Macrosteles
. Other insect feeders include caterpillars of Cisseps
(Yellow-Collared Scape Moth) and possibly
(Poweshiek Skipperling). Some of these insect
associated with wet prairies and they are quite rare. The seedheads of
spikerushes are eaten by such wetland birds as rails, coots, ducks, and
geese (see Wetland Bird Table
In addition, the foliage and/or roots
are eaten by the Canada Goose and muskrats (Martin et al., 1951/1961;
Hamerstrom & Blake, 1939).
Along the shore of a pond near Champaign,
This is one of the smallest spikerushes (Eleocharis spp.
within Illinois. It can be
reliably distinguished from other small species in this genus by its
achenes: each of
its achenes has a distinctive oblanceoloid or obovoid shape, a small
conical tubercle with a swollen base, and 9-15 longitudinal ribs. An
exception to this rule is Eleocharis
(Wolf's Spikerush), which
has very similar achenes. However, this latter species is a taller
spikerush with wider culms (0.5-1.0 mm. across) and longer scales
on its spikelets (2.5-3.0 mm. in length). Without the spikelets and
achenes, Needle Spikerush cannot be reliably distinguished from Eleocharis
(Intermediate Spikerush) and other small