Digitaria insularis |
Digitaria cognata |
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sourgrass |
Carolina cottontop, Carolina crabgrass, fall crabgrass, fall witchgrass |
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Habit | Plants perennial; cespitose, shortly rhizomatous, with knotty bases. | Plants perennial; cespitose, without rhizomes. |
Culms | 80-130 cm, erect, with densely villous cataphylls, branching from the lower and middle nodes. |
30-56 cm, erect; nodes glabrous. |
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. |
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Leaves | mainly cauline; sheaths glabrous or sparsely to densely pubescent, sometimes with papillose-based hairs; ligules 0.2-1.5 mm, entire to lacerate; blades 2.4-12.6 cm long, 2-5.4 mm wide, glabrous or pubescent. |
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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. |
simple, 12.8-27.5 cm long, 16.5-44.5 cm wide, open; branches divergent; lower primary branches 10.5-24 cm, often with 1-several sterile branches near the base; pedicels divergent, spikelets solitary. |
Spikelets | 5.5-8.2 mm (including pubescence), 4.2-5.9 mm (excluding pubescence), narrowly ovate, acuminate. |
2.2-3.1 mm long, 0.7-1.1 mm wide, obovate or broadly 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. |
0.1-0.8 mm; upper glumes 1.8-2.8 mm, 3(5)-veined, glabrous or pubescent between the veins, hairs appearing as a narrow stripe; lower lemmas similar to the upper glumes in length, texture, and pubescence, 7-veined, veins unequally spaced, lateral veins closer together than the 3 central veins; upper lemmas 1.9-2.9 mm, glabrous, dark brown, narrowly acute; anthers 0.5-0.7 mm, yellow or purple. |
Caryopses | 1.3-1.6 mm. |
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2n | = 36. |
= 36. |
Digitaria insularis |
Digitaria cognata |
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Distribution |
AL; AZ; FL; IL; MS; TX; HI; PR; Virgin Islands
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AL; AR; CT; DE; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; MI; MN; MO; MS; NC; NE; NH; NJ; NY; OH; OK; PA; SC; TN; TX; VA; VT; WI; ON
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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 cognata grows in dry, sandy soils in the eastern portion of the Flora region from southern Ontario and Vermont through the United States and thence to southern Mexico. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 25, p. 370. | FNA vol. 25, p. 362. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Trichachne insularis | Leptoloma cognatum |
Name authority | (L.) Mez ex Ekman | (Schult.) Pilg. |
Web links |