Digitaria

Plants annual, perennial, or of indefinite duration. Culms 5-250 cm, erect or decumbent, branching basally or at aerial culm nodes, when annual or of indefinite duration usually decumbent and rooting at the lower nodes. Sheaths open; ligules membranous, sometimes ciliate; blades usually flat. Inflorescences terminal, sometimes also axillary, usually panicles of 1-sided spikelike branches (sometimes only 1 branch) attached digitately or racemosely to a rachis, sometimes simple panicles of solitary, pedicellate spikelets; spikelike branches, if present, sometimes with secondary branches, primary branch axes triquetrous, bearing spikelets abaxially, in 2 rows, usually in unequally pedicellate groups of 2-5, occasionally borne singly. Spikelets 1.2-8.2 mm, lanceoloid to ellipsoid, dorsally compressed, apices obtuse to acuminate, unawned, with 2 florets; disarticulation beneath the glumes. Lower glumes absent or to 1/4 as long as the spikelets; upper glumes usually from 1/6 as long as to equaling the spikelets, occasionally absent, 0-5-veined, usually pubescent; lower florets sterile; lower lemmas membranous, usually as long as the upper lemmas, usually pubescent, (3)5-7(13)-veined; lower paleas absent or reduced; upper lemmas mostly stiffly chartaceous to cartilaginous, obscurely veined, with 0.5-1 mm hyaline margins that embrace the upper paleas; upper paleas similar to the upper lemmas in texture and size; lodicules 3, cuneate; anthers 3. Caryopses plano-convex; embryos 1/5–1/2 as long as the caryopses; hila punctiform to ellipsoid, x = 9.

Distribution

N.C., Conn., N.J., N.Y., Wash., Va., Del., D.C, Wis., W.Va., Pacific Islands (Hawaii), Md., Alta., B.C., Man., N.B., N.S., Ont., P.E.I., Que., Sask., Mass., Maine, N.H., R.I., Vt., Fla., Wyo., Tenn., N.Mex., Tex., La., Ala., Miss., Okla., S.C., Pa., Ariz., Nev., Puerto Rico, Colo., Ind., Virgin Islands, Calif., Kans., N.Dak., Nebr., S.Dak., Ark., Ill., Ga., Iowa, Idaho, Mont., Oreg., Ohio, Utah, Mo., Minn., Mich., Ky.

Discussion

Digitaria has approximately 200 species and grows primarily in tropical and warm-temperate regions, often in disturbed, open sites. Some species are grown as cereals; others for forage or as lawn grasses. In North America, the genus is best known for two of its weedy species, D. sanguinalis and D. ciliaris. There are 29 species known to occur in the Flora region; 18 are native to the region.

Most annual species of Digitaria will survive several years in regions without a pronounced cold season; such species are described as being of indefinite duration.

Selected References

Boonbundarl, S. 1985. A biosystematic study of the Digitaria leucites complex in North America. Ph.D. dissertation, Texas A&M University, College Station, Texas, U.S.A. 238 pp.

Gould, F.W. 1975. The Grasses of Texas. Texas A&M University Press, College Station, Texas, U.S.A. 653 pp.

Henrard, J. 1950. Monograph of the genus Digitaria. Universitaire Pers Leiden, Leiden, The Netherlands. 999 pp.

Kartesz, J. and C.A. Meacham. 1999. Synthesis of the North American Flora, Version 1.0 (CD-ROM). North Carolina Botanical Garden, Chapel Hill, North Carolina, U.S.A.

Kok, P.D.F., P.J. Robbertse, and A.E. van Wyk. 1989. Systematic study of Digitaria section Digitaria (Poaceae) in southern Africa. S. African J. Bot. 55:141-153

Veldkamp, J.F. 1973. A revision of Digitaria in Malesia. Blumea 21:1-80

Webster, R.D. 1981. A biosystematic study of the Digitaria sanguinalis complex in North America (Poaceae). Ph.D. dissertation, Texas A&M University, College Station, Texas. 156 pp.

Webster, R.D. and S.L. Hatch. 1981. Taxonomic relationships of Texas specimens of Digitaria ciliaris and Digitaria bicornis (Poaceae). Sida 9-3A-A2

Webster, R.D. 1983. A revision of the genus Digitaria Haller (Paniceae: Poaceae) in Australia. Brunonia 6:131-216

Webster, R.D. 1987. Taxonomy of Digitaria section Digitaria in North America (Poaceae: Paniceae). Sida 12:209-222

Webster, R.D. and S.L. Hatch. 1990. Taxonomy of Digitaria section Aequiglumae (Poaceae: Paniceae). Sida 14:145-167

Wipff, J.K. and S.L. Hatch. 1994. A systematic study of Digitaria sect. Pennatae (Poaceae: Paniceae) in the New World. Syst. Bot. 19:613-627.

Lower Taxa

Digitaria abyssinica, Digitaria arenicola, Digitaria bakeri, Digitaria bicornis, Digitaria californica, Digitaria ciliaris, Digitaria cognata, Digitaria didactyla, Digitaria eriantha, Digitaria filiformis, Digitaria floridana, Digitaria gracillima, Digitaria hitchcockii, Digitaria horizontalis, Digitaria insularis, Digitaria ischaemum, Digitaria leucocoma, Digitaria longiflora, Digitaria milanjiana, Digitaria nuda, Digitaria patens, Digitaria pauciflora, Digitaria pubiflora, Digitaria sanguinalis, Digitaria serotina, Digitaria setigera, Digitaria simpsonii, Digitaria texana, Digitaria tomentosa, Digitaria velutina, Digitaria violascens

Key

1	Inflorescences simple open panicles, with well-developed primary and secondary branches; branches and pedicels divergent; spikelets solitary.	> 2
2	Upper glumes absent or to 0.6 mm long, veinless	Digitaria tomentosa
2	Upper glumes 1.8-3.8 mm long, 3-7-veined.	> 3
3	Spikelets 3.5-4.6 mm long; upper glumes 5-7-veined	Digitaria arenicola
3	Spikelets 2.2-3.3 mm long; upper glumes 3(5)-veined.	> 4
4	Lower lemmas 7-veined, veins not equally spaced	Digitaria cognata
4	Lower lemmas 5-veined, veins equidistant	Digitaria pubiflora
1	Inflorescences panicles of spikelike branches; secondary branches rarely present; spikelets appressed to the branches, in groups of 2-5 on the middle portion of the primary branches.	> 2
5	Spikelets in groups of 3-5 on the middle portions of the primary branches, the longer pedicels in each group often adnate to the branch axes for part of their length.	> 6
6	Upper lemmas pale yellow or gray when immature, light brown to brown when mature, sometimes purple-tinged.	> 7
7	Upper glumes 1/6-1/3 long as the spikelets; sheaths and blades pubescent	Digitaria serotina
7	Upper glumes equaling or almost equaling the spikelets; sheaths and blades usually glabrous.	> 8
8	Upper glumes 5-veined; spikelets elliptic to obovate; plants stoloniferous	Digitaria longiflora
8	Upper glumes 3-veined; spikelets lanceolate; plants not stoloniferous	Digitaria floridana
6	Upper lemmas brown when immature, becoming dark brown when mature.	> 7
9	Primary panicle branches wing-margined, the wings at least 1/2 as wide as the midribs.	> 10
10	Plants always with axillary panicles in the lower leaf sheaths, these panicles sometimes completely concealed by the sheaths; spikelets 1.7-2.3 mm long	Digitaria ischaemum
10	Plants without axillary panicles; spikelets 1.2-1.7 mm long.	> 11
11	Primary panicle branches, if more than 2, racemose, the terminal branches erect, the other branches usually divergent; upper lemmas light brown to brown at maturity; upper glumes almost as long as the upper lemmas	Digitaria floridana
11	Primary panicle branches usually all digitate, sometimes 1 below the others, all the branches erect to ascending; upper lemmas dark brown at maturity; upper glumes 1/2 as long as to almost equaling the upper lemmas	Digitaria violascens
9	Primary panicle branches not wing-margined or the wings not as wide as the midribs.	> 10
12	Lower lemmas pubescent.	> 13
13	Plants annual, or short-lived perennials, branching at the lower nodes; cauline nodes 3-6	Digitaria filiformis
13	Plants perennial, not branching at the lower nodes; cauline nodes 1-2.	> 14
14	Upper glumes and lower lemmas with long, glandular-tipped hairs along their margins and intercostal regions	Digitaria leucocoma
14	Upper glumes and lower lemmas glabrous over most of their length, sparsely pubescent near the apices, the hairs short, not glandular-tipped	Digitaria bakeri
12	Lower lemmas glabrous.	> 13
15	Upper glumes less than 1/2 as long as the spikelets	Digitaria gracillima
15	Upper glumes more than 1/2 as long as the spikelets.	> 16
16	Plants annual, branching at the lower nodes; culm nodes 3-6; upper glumes obtuse	Digitaria filiformis
16	Plants perennial, not branching at the lower nodes; culm nodes 1-2; upper glumes acute	Digitaria bakeri
5	Spikelets paired on the middle portions of the primary branches; pedicels not adnate to the branch axes.	> 6
17	Upper lemmas brown when immature, almost always dark brown when mature; primary branches not wing-margined or with wings less than 1/2 as wide as the midribs.	> 18
18	Spikelets (including pubescence) 1.3-3.1 mm long; lower lemmas (including pubescence) shorter than or no more than 0.5 mm longer than the upper florets; ligules 0.1-1.5 mm long, ciliate; lower lemmas sparsely to densely pubescent, the hairs less than 1 mm long, appressed, not spreading at maturity.	> 19
19	Lower glumes 0.3-1 mm long; plants perennial, with hard, knotty, shortly rhizomatous bases; culms erect, not rooting at the lower nodes; lower lemmas 5-veined, the veins equally spaced	Digitaria hitchcockii
19	Lower glumes absent or to 0.1 mm long; plants annual, or short-lived perennials; culms erect or decumbent, sometimes rooting at the lower nodes; lower lemmas 5-7-veined, the veins unequally spaced, the outer veins closely spaced.	> 20
20	Upper lemmas dark brown at maturity; lower primary panicle branches without secondary branches; upper glumes with clavate to capitate hairs	Digitaria filiformis
20	Upper lemmas usually gray, sometimes brown, at maturity; lower primary panicle branches with strongly divergent secondary branches; upper glumes with tapering or parallel-sided hairs	Digitaria velutina
18	Spikelets (including pubescence) 3.7-7.5 mm long; lower lemmas (including pubescence) exceeding the upper florets by 0.8 mm or more; ligules 1-6 mm long, not ciliate; lower lemmas densely pubescent, the hairs 1-6 mm long, usually spreading at maturity.	> 19
21	Terminal pedicels of primary branches 7.4-20 mm long; primary branches usually divergent, sometimes ascending, at maturity, the middle internodes (4.5)6-15 mm long	Digitaria patens
21	Terminal pedicels of primary branches 1.7-6(7) mm long; primary branches appressed to ascending at maturity, the middle internodes 2-6 mm long.	> 22
22	Lower lemmas pubescent between most, sometimes all, of the veins and on the margins	Digitaria insularis
22	Lower lemmas glabrous between the veins, pubescent on the margins, sometimes also on the lateral veins	Digitaria californica
17	Upper lemmas pale yellow, tan, or gray, sometimes purple-tinged, when immature; gray, yellow, tan, light brown, or purple at maturity; primary branches sometimes wing-margined, the margin widths various.	> 18
23	Primary panicle branches not or only narrowly wing-margined, the wings no more than 1/2 as wide as the midribs.	> 24
24	Spikelets 1.5-2.5 mm long.	> 25
25	Upper glumes glabrous; plants rhizomatous; culms decumbent but usually not rooting at the lower nodes	Digitaria abyssinica
25	Upper glumes shortly villous on the margins, sometimes also elsewhere; plants not rhizomatous; culms erect or decumbent and rooting at the lower nodes	Digitaria texana
24	Spikelets 2.5-3.6 mm long.	> 25
26	Culms usually branching at the aerial nodes, not rooting at the lower nodes; leaf blades 2-2.2 mm wide, flat or folded; upper glumes glabrous	Digitaria pauciflora
26	Culms not branching at the aerial nodes, often rooting at the lower nodes; leaf blades 2-7mm wide, flat; upper glumes villous or glabrous.	> 27
27	Upper glumes 7-9-veined, glabrous or obscurely pubescent; plants of indefinite duration	Digitaria simpsonii
27	Upper glumes (3)5-veined, shortly villous on the margins and sometimes between the margins; plants perennial	Digitaria texana
23	Primary branches winged, the wings at least 1/2 wide as the midribs.	> 24
28	Plants perennial, usually stoloniferous, sometimes also rhizomatous.	> 29
29	Leaf blades 1-3 mm wide; panicles with 2-4 primary branches, the branches 2-7 cm long	Digitaria didactyla
29	Leaf blades 3-13 mm wide; panicles with 2-18 primary branches, the branches 5-25 cm long.	> 30
30	Midveins of the lower lemmas scabrous, at least on the distal 1/2	Digitaria milanjiana
30	Midveins of the lower lemmas smooth throughout	Digitaria eriantha
28	Plants annual or of indefinite duration, usually neither rhizomatous nor stoloniferous.	> 29
31	Lateral veins of the lower lemmas scabrous for the distal 2/3 of their length, sometimes scabrous throughout (use 20x magnification); leaf blades usually with papillose-based hairs on both surfaces	Digitaria sanguinalis
31	Lateral veins of the lower lemmas smooth throughout or scabrous only on the distal 1/3; leaf blades with or without papillose-based hairs.	> 32
32	Lower lemmas of the lower spikelets of each pair 7-veined, the 2 lateral veins on each side crowded together near the margins, the 3 central veins equally spaced.	> 33
33	Lower primary panicle branches with strongly divergent secondary branches	Digitaria velutina
33	Lower primary panicle branches without secondary branches.	> 34
34	Spikelets 2.6-3.7 mm long; spikelets dimorphic with respect to their pubescence; lower lemmas of the upper spikelets of each spikelet pair with marginal hairs that become widely divergent at maturity; lower lemmas of the lower spikelets in each pair glabrous or with hairs that remain appressed at maturity; lowest panicle nodes glabrous or with hairs less than 0.4 mm long	Digitaria bicornis
34	Spikelets 1.7-2.8 mm long; spikelets homomorphic with respect to their pubescence; lowest panicle nodes with hairs more than 0.4 mm long.	> 35
35	Adaxial surfaces of the blades evenly, sometimes densely, hairy; leaf sheaths usually with scattered hairs; upper glumes 1/3 – 1/2 as long as the spikelets	Digitaria horizontalis
35	Adaxial surfaces of the blades glabrous or with a few long hairs near the base; leaf sheaths glabrous or with a few long hairs near the base; upper glumes 2/5 - 4/5 as long as the spikelets	Digitaria nuda
32	Lower lemmas of the lower spikelets of each pair 5- or 7-veined, the 2 or 3 lateral veins on each side crowded together near the margins, well-separated from the midvein.	> 33
36	Lower glumes absent or no more than 0.1 mm long.	> 37
37	Anthers 0.6-1.3 mm long; upper glumes 0.2-1.3 mm long, less than 0.4 times as long as the spikelets	Digitaria setigera
37	Anthers 0.3-0.6 mm; upper glumes 1-2.2 mm long, 0.4-0.8 times as long as the spikelets	Digitaria nuda
36	Lower glumes 0.1-0.8 mm long.	> 37
38	Lower glumes 0.2-0.8 mm long; primary branches glabrous or with hairs shorter than 1 mm; spikelets 2.7-4.1 mm long	Digitaria ciliaris
38	Lower glumes 0.1-0.2 mm long; primary branches often with scattered hairs 1-4 mm long; spikelets 1.7-2.8 mm long.	> 39
39	Adaxial surfaces of the blades evenly hairy, sometimes densely so; leaf sheaths usually with scattered hairs; upper glumes 0.3-0.5 times as long as the spikelets	Digitaria horizontalis
39	Adaxial surfaces of the blades glabrous or with a few long hairs near the base; leaf sheaths glabrous or with a few long hairs near the base; upper glumes 0.4-0.8 as long as the spikelets	Digitaria nuda