Plants annual; cespitose, without innovations. Culms
10-50 cm, erect to geniculate, glabrous, often with glandular pits below the
nodes. Sheaths mostly glabrous, apices hirsute, hairs to 4 mm, often
also with glandular pits; ligules 0.2-0.5 mm, ciliate; blades
(2)4-10(21) cm long, 1-4 mm wide, flat to involute, glabrous abaxially, scabridulous
adaxially. Panicles 4-20 cm long, less than 1/2 the height of the plants,
2-10(14) cm wide, narrowly elliptic, open; primary branches 2-6 cm, compact,
diverging 20-70° from the rachises, capillary, sometimes with glandular
pits, naked basally; pulvini glabrous; pedicels 1.5-5 mm, divergent.
Spikelets (1.7)2-4(5.6) mm long, 1-2(2.5) mm wide, broadly ovate to lanceolate,
plumbeous to reddish-purple, with 3-6 florets; disarticulation acropetal,
paleas persistent. Glumes narrowly lanceolate to lanceolate, hyaline;
lower glumes 1-1.5 mm; upper glumes 1-1.8 mm; lemmas 1.1-1.6
mm, broadly ovate, membranous, lateral veins inconspicuous, apices acute; paleas
1-1.5 mm, hyaline, keels scabridulous, apices obtuse; anthers 2 or 3,
0.2-0.3 mm, purplish. Caryopses 0.4-0.7 mm, ovoid to rectangular-prismatic,
striate, reddish-brown, adaxial surfaces flat or shallowly grooved, distal 2/3
opaque. 2n
= 40, 80.
Eragrostis frankii
is native in the central and eastern United States,
but it has been found, as an introduction, in southern Ontario, and appears
to be increasingly common in the northeastern United States. It grows in moist
meadows, along streams and sand bars, in forest openings, and along roadsides,
at 5-1500 m, usually in association with Pinus, Quercus, Acer,
and Fagus grandiflora. The record from Santa Fe County, New Mexico, is
based on a specimen collected by Fendler in 1847; there are no other collections
from the state. Fendlers specimens seem to represent either an accidental introduction
that did not become established or a labeling error.
Eragrostis frankii
is similar to E.
capillaris, but differs in its frequent possession of glandular pits,
its flat or more shallowly grooved caryopses, shorter pedicels, and glabrous
sheath margins, and in having panicles that are usually less than half as long
as the culms.
Annual 1-5 dm, the culms densely cespitose, repeatedly branched; lvs 1-4 mm wide; middle sheaths mostly longer than their internodes; infl 5-20 cm, ellipsoid, rather compactly branched, the middle branches the longest, the lower ones solitary or rarely paired; pedicels spreading; spikelets 3-6(-9)-fld, 1-2.5 mm wide; first glume 1-1.5 mm, three-fourths to one and one-fourth times as long as the lowest lemma; lemmas 1.1-1.6 mm, individually deciduous from the rachilla, on which the paleas persist; grain 0.5-0.7 mm, broadly ellipsoid to subglobose, somewhat compressed, sometimes shallowly indented on one side; 2n=40, 80. Riverbanks, sand-bars, and moist ground; Mass., Vt. and s. Que. to Minn., s. to Fla. and Ark.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.