This perennial grass produces leafy culms about 2-3' long that
eventually lean to the side when they develop their inflorescences.
The culms are medium green, terete, and unbranched. Alternate leaves
occur along the lower one-third of each flowering culm; their blades are widely
spreading and arch toward the ground. The leaf blades are up to ¾"
across and 24" long; they are dark green, glabrous, and
slightly rough-textured along their margins. The leaf sheaths are
usually glabrous, although sometimes short-pubescent. The nodes along
each culm are light-colored and slightly swollen. Leaf venation is
parallel; sometimes the midveins of the blades are off-center.
culms produce only leaves and remain short, while fertile
culms become long and produce terminal inflorescences on long naked
stalks. Each inflorescence consists of a narrow raceme-like panicle of
spikelets about 4-12" long. The lateral branches of the inflorescence
are few in number and erect (relative to the central axis); they are 1-4"
long and either sparingly branched or unbranched. Both the central axis
and lateral branches of the panicle are narrow, somewhat angular, and
often rough-textured from minute stiff hairs. Individual spikelets of
the lateral branches have a pair of glumes at the bottom, and
lemmas, paleas, and their florets above. Sometimes the
uppermost lemma of a spikelet is sterile and empty. The first glumes
are 2.0-3.5 mm. long, ovate, usually single-veined, and
second glumes are 2.5-5.0 mm. long, lanceolate or elliptic, 3- to
5-veined, and glabrous. The lemmas are obovate or broadly elliptic with
membranous margins; they are 4.5-7.0 mm. long, glabrous, and
keeled, tapering abruptly to short narrow tips. The paleas are similar to the
lemmas, but shorter and less pointed. The florets are perfect. The blooming period
occurs during mid-summer for about 2 weeks. Later, the spikelets change
from green to tan as they become mature; fertile florets are replaced
by large exerted grains about 4-6 mm. long. These grains are obovoid in
shape, but they have long beaks with blunt tips. Disarticulation of the
spikelets is above the glumes. The root system is fibrous and
rhizomatous. Vegetative colonies of plants often develop from the
This grass prefers light shade, moist to dry-mesic
conditions, and soil containing loam or silt-loam with abundant
decaying leaves. It can be propagated by seed or division of the
rhizomes, and used as a ground cover in shaded areas.
The native Beak Grass is scattered
Illinois; this grass is occasional in high
quality natural areas, otherwise it is uncommon to absent. Habitats
consist of upland woodlands to floodplain woodlands, wooded slopes
along bluffs, and shaded limestone cliffs. In floodplain woodlands, the
grains of this grass can be distributed by water. Various deciduous
trees are dominant in the preceding habitats.
Information about floral-faunal
this grass are unavailable. Clearly more research in this area is
needed. The large seeds are probably an attractive source of food
to upland gamebirds and small rodents that inhabit wooded
Along a wooded slope at Fox Ridge State Park in
Coles County, Illinois.
Beak Grass has very distinctive grains that are
large in size
and oddly shaped. On this basis, it is easily distinguished from other
grasses that are outside its genus. In the past, Beak Grass was
considered a variety of American Beak Grass, or Diarrhena americana
. However, it is now considered a distinct species
with a more
northern range. In Illinois, Beak Grass is more common and widely
distributed than American Beak Grass; the latter is restricted to the
southern tip of Illinois, where it is rare. These two species can be
distinguished from each other as follows: 1) Beak Grass (Diarrhena
) has lemmas that are less than 7.0 mm. long, while
of American Beak Grass (Diarrhena
) are often greater than 7.0 mm.
long; 2) the width of the mature grains for Beak Grass exceeds 1.8 mm.
across, while the mature grains of American Beak Grass are less than
1.8 mm. across; and 3) the central axis of the inflorescence for Beak
has minute hairs that are less than 0.5 mm. in length, while the
central axis of the inflorescence for American Beak Grass has some
hairs that exceed 0.5 mm. in length. In the absence of their
inflorescences, these two species are difficult to distinguish, but
American Beak Grass tends to more pubescent overall than Beak Grass.