The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links

sourgrass

digitaire astringente, smooth crab grass

Habit Plants perennial; cespitose, shortly rhizomatous, with knotty bases. Plants annual or of indefinite duration.
Culms

80-130 cm, erect, with densely villous cataphylls, branching from the lower and middle nodes.

20-55(70) cm, decumbent, branching and rooting at the lower nodes;

nodes 3-4.

Sheaths

usually sparsely to densely papillose-hirsute, occasionally glabrous;

ligules 4-6 mm, usually lacerate, not ciliate;

blades 20-50 cm long, 10-17 mm wide, lax, smooth or scabridulous abaxially, scabridulous to scabrous adaxially.

glabrous or sparsely pubescent;

ligules 0.6-2.5 mm;

blades 1.5-9 cm long, 3-5 mm wide, glabrous, with a few papillose-based hairs basally.

Panicles

20-35 cm long, 2-10 cm wide, with numerous spikelike primary branches;

primary branches 10-15 cm, appressed to ascending at maturity, axes not wing-margined or with wings less than 1/2 as wide as the midribs;

internodes 3-4.5(6) mm (midbranch), bearing spikelets in unequally pedicellate pairs;

secondary branches rarely present;

pedicels not adnate to the branches;

shorter pedicels 0.7-2 mm;

longer pedicels 2.5-5 mm;

terminal pedicels 2-5 mm.

terminal and axillary;

terminal panicles with 2-7 spikelike primary branches, subdigitate or on 0.5-2 cm rachises;

primary branches 6-15.5 cm, axes wing-margined, wings at least 1/2 as wide as the midribs, bearing spikelets in groups of 3, lower portions of the longer pedicels adnate to the axes;

secondary branches rarely present;

axillary inflorescences always present in some of the lower sheaths, entirely or partially concealed.

Spikelets

5.5-8.2 mm (including pubescence), 4.2-5.9 mm (excluding pubescence), narrowly ovate, acuminate.

1.7-2.3 mm, homomorphic, narrowly elliptic.

Lower glumes

0.6-0.8 mm;

upper glumes 3.5-4.5 mm, 3-5-veined, pubescent on the margins;

lower lemmas 4.1-5.7 mm (exceeded 1.5-5 mm by pubescence), narrowly ovate, 7-veined, pubescent between most, sometimes all, of the veins and on the margins, veins usually obscured by a dense covering of golden-brown hairs, hairs 3-6 mm, spreading at maturity, intercostal regions on either side of the midvein glabrous or pubescent with shorter, fine, white hairs, sometimes intermixed with the golden-brown hairs;

upper lemmas 3.2-4.5 mm, narrowly ovate, brown when immature, dark brown at maturity, acuminate;

anthers 1-1.2 mm.

absent or a veinless, membranous rim;

upper glumes 1.3-2.3 mm, from 3/4 as long as to equaling the upper lemmas, appressed-pubescent;

lower lemmas 1.7-2.3 mm, 7-veined, veins unequally spaced, smooth, pubescent;

upper lemmas dark brown at maturity;

anthers 0.4-0.6 mm.

2n

= 36.

= 36.

Digitaria insularis

Digitaria ischaemum

Distribution
from FNA
AL; AZ; FL; IL; MS; TX; HI; PR; Virgin Islands
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; PR; AB; BC; MB; NB; NS; ON; PE; QC; SK; Virgin Islands
[WildflowerSearch map]
[BONAP county map]
Discussion

Digitaria insularis grows in low, open ground of the southern United States, and extends to the West Indies, Mexico, and through Central America to Argentina.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Digitaria ischaemum is a Eurasian weed that is now common in lawns, gardens, fields, and waste ground in warm-temperate regions throughout the world, including much of the Flora region. Larger plants with 5-7 inflorescence branches 8-15 cm long have been called var. mississippiensis (Gatt.) Fernald, but they intergrade with more typical plants, and so do not merit taxonomic recognition.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 25, p. 370. FNA vol. 25, p. 372.
Parent taxa Poaceae > subfam. Panicoideae > tribe Paniceae > Digitaria Poaceae > subfam. Panicoideae > tribe Paniceae > Digitaria
Sibling taxa
D. abyssinica, D. arenicola, D. bakeri, D. bicornis, D. californica, D. ciliaris, D. cognata, D. didactyla, D. eriantha, D. filiformis, D. floridana, D. gracillima, D. hitchcockii, D. horizontalis, D. ischaemum, D. leucocoma, D. longiflora, D. milanjiana, D. nuda, D. patens, D. pauciflora, D. pubiflora, D. sanguinalis, D. serotina, D. setigera, D. simpsonii, D. texana, D. tomentosa, D. velutina, D. violascens
D. abyssinica, D. arenicola, D. bakeri, D. bicornis, D. californica, D. ciliaris, D. cognata, D. didactyla, D. eriantha, D. filiformis, D. floridana, D. gracillima, D. hitchcockii, D. horizontalis, D. insularis, D. leucocoma, D. longiflora, D. milanjiana, D. nuda, D. patens, D. pauciflora, D. pubiflora, D. sanguinalis, D. serotina, D. setigera, D. simpsonii, D. texana, D. tomentosa, D. velutina, D. violascens
Synonyms Trichachne insularis Syntherisma linearis, Syntherisma ischaemum
Name authority (L.) Mez ex Ekman (Schreb.) Muhl.
Web links