Plants annual, or short-lived perennials; cespitose, not rhizomatous.
Culms (10)25-150 cm, erect or decumbent, branching, sometimes rooting
at the lower nodes; nodes 3-6. Sheaths keeled, basal sheaths usually
with papillose-based hairs, rarely glabrous; ligules 0.3-1.5 mm; blades
2-18 cm long, 1-6 mm wide, flat or involute, glabrous, scabrous, or pilose.
Panicles with 2-7 spikelike primary branches, these digitate or the rachises
to 1 cm; longest primary branches 3-25 cm long, 0.2-0.4 mm wide, axes
triquetrous, not wing-margined, with spikelets in groups of 2-5 on the lower
and middle portions. Spikelets 1.3-2.8 mm. Lower glumes absent
or to 0.1 mm; upper glumes 1-2 mm long, from 3/4 to almost as long as
the spikelets, almost glabrous or sparsely to densely pubescent with clavate
to capitate hairs (use 20× magnification), glume apices rounded; lower
lemmas equaling the spikelets, glabrous or glandular-pubescent, 5-7-veined,
veins unequally spaced, outer 3 veins on each side closer to each other than
the midvein is to the inner lateral veins; upper lemmas 1.3-2 mm, apiculate,
dark brown at maturity; anthers 0.3-0.6 mm. 2n = 36, 54.
Digitaria filiformis grows throughout the warmer parts of the eastern
United States. Digitaria filiformis var. filiformis, the most widespread
of its varieties, extending into Mexico.
Annual herb, tufted 10 cm - 1.5 m tall Leaves: alternate, two-ranked. Sheaths open, keeled. Basal sheaths with bumpy-based hairs. Ligules to 1.5 mm long, membranous. Blades 2 - 18 cm long, 1 - 6 mm wide, flat or with rolled-up margins, parallel-veined, sometimes softly or roughly hairy. Inflorescence: a terminal arrangement of spikelet-bearing branches (panicle). Primary branches two to seven, palmate (or the axis to 1 cm), 3 - 25 cm long, to 0.5 mm wide, spike-like, bearing spikelets in groups of two to five along the middle and lower regions. Fruit: a caryopsis, indehiscent, enclosed within the persistent lemma and palea, flat on one side and convex on the other (plano-convex). Culm: decumbent or upright, branched, 10 cm - 1.5 m long, round in cross-section, occasionally rooting at the lower nodes. Nodes three to six. Spikelets: 1.5 - 2.5 mm long. Florets: two per spikelet. Lower florets sterile. Upper florets bisexual. Anthers three, about 0.5 mm long. Stigmas red. Glumes:: Lower glumes absent or to 0.1 mm long. Upper glumes 1 - 2 mm long, three fourths to nearly as long as spikelet, rounded at the apex, nearly hairless to densely hairy. Lemmas:: Lower lemmas equal to spikelets, five- to seven-veined (unequally spaced), membranous, sometimes glandular-hairy. Upper lemmas brown, 1.5 - 2 mm long, short-pointed at the apex, obscurely veined, with margins that embrace the upper paleas. Paleas:: Lower paleas absent. Upper paleas similar in size and texture to upper lemmas.
Similar species: No information at this time.
Flowering: August to September
Habitat and ecology: Found in the sandy soil of woodlands and prairies.
Occurence in the Chicago region: native
Etymology: Digitaria comes from the Latin word digitus, meaning finger, referring to the digitate inflorescence of some species. Filiformis means thread-like.
Branched from the base, erect or ascending; blades 2-6 mm wide, flat, at least the lower commonly pilose; racemes 2-6, erect or ascending, often distinctly separated at base; rachis triquetrous, scarcely winged; spikelets in pairs or threes, well separated and scarcely overlapping; first glume lacking; the second three-fifths to three-fourths as long as the spikelet, usually pubescent and erose-ciliate with capitellate hairs; fertile lemma dark brown or purple; 2n=36. Fields and open ground, often a troublesome weed southward. Forms with glabrous spikelets occur in both vars. (D. laeviglumis)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.