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

sourgrass

Jamaican crabgrass

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

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

to 1 m, erect portion 20-25 cm, decumbent, rooting and branching freely at the nodes.

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.

usually with scattered papillose-based hairs, hairs more abundant on the lower sheaths;

ligules 1.5-1.8 mm, erose;

blades 3-14 cm long, 3-9 mm wide, evenly, often densely pubescent adaxially, hairs papillose-based.

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.

with 2-14 spikelike branches attached to 4-15 cm rachises, lower branches whorled, upper branches often paired or solitary;

lower nodes with hairs more than 0.4 mm;

primary branches 4-12 cm, axes 0.4-0.7 mm wide, wing-margined, wings at least 1/2 as wide as the midribs, often with scattered 1-4 mm hairs proximally, bearing spikelets in unequally pedicellate pairs on the proximal and middle portion of the branches;

secondary branches rarely present;

shorter pedicels 0.3-0.5 mm;

longer pedicels 1.3-2 mm.

Spikelets

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

homomorphic, 2.1-2.4 mm, narrowly ovate.

Caryopses

about 1.8 mm, tan.

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.

glumes 0.1-0.2 mm;

upper glumes 1-1.1 mm, 1/3 – 1/2 as long as the spikelets, 3-veined, margins and apices ciliate;

lower lemmas about as long as the spikelets, lanceolate, 7-veined, lateral 3 veins on each side unequally or equally spaced, smooth or scabrous over the distal 1/3, lemma margins and the region between the second and third veins densely pubescent, hairs 0.05-0.1 mm, white;

upper lemmas slightly shorter than the lower lemmas, yellowish or grayish when immature, becoming light brown at maturity, minutely striate.

2n

= 36.

= 36.

Digitaria insularis

Digitaria horizontalis

Distribution
from FNA
AL; AZ; FL; IL; MS; TX; HI; PR; Virgin Islands
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; FL; MS; SC; HI; PR; Virgin Islands
[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 horizontalis is native to tropical regions of the Americas. It has been found in hammocks and disturbed areas in central and southern Florida and at a few other locations in the southeastern United States, including ballast dumps in Mobile, Alabama. It is probably a recent introduction to the Flora region, even in Florida.

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

Source FNA vol. 25, p. 370. FNA vol. 25, p. 378.
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. insularis, 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
Synonyms Trichachne insularis
Name authority (L.) Mez ex Ekman Willd.
Web links