Digitaria is from the Latin digitus meaning finger and refers to the finger like seed head. Summer grass - because if grows and flowers in summer.
Creeping stemmed, striped sheathed annual grass with rough leaves and a seed head with 2-12 fingers. 100-1000 mm tall. Sometimes with a purplish tinge.
Alternate. Mainly on the stems. Blade - Green or tinged with purple, 30-300 long by 3-12 mm wide. Wavy, slightly thickened and roughened edges. Flat, soft, rough to touch on both surfaces, limp and weak. Rounded or contracted near the base. Tapers to a point. Hairless or a few hairs near the base or on the upper surface. Midrib whitish. Ligule - Membranous, flat or ragged on top. 1-2 mm long. With a few hairs behind it. Auricles - Sheath - Striped. Hairy on the edges and on the lower leaves with tubercle (wart) based hairs.
Creeping, soft, tufted, sometimes erect or with a knee like bend near the base. Up to 1000 mm long. Nodes are hairy, otherwise hairless. Often channelled on one side. Roots at the nodes. Branched at the lower nodes, unbranched at the upper nodes.
Raceme. 2-12 fingers, 30-300 mm long, initially erect but later spreading outwards. Main axis 3 angled, 20-40 mm long, and more or less in 2 rings (whorls). Branch axis is small, toothed and winged (0.5-1 mm wide). Spikelets in pairs on unequal stalks, pressed along one side, slightly overlapping and all the way to the base of the fingers.
Spikelets - Pale green to purplish, 2.5-3.5 mm long by 0.7-0.8 mm wide, lance shaped, 2 flowered. Pointed tip. Overlapping stalks of varying lengths. Fall to ground intact on maturity. Hairless or hairy but not silky hairy. Florets - Flattened. Glumes - Lower, triangular, 0.2-0.5 mm long. Upper one has 3 smooth nerves, hairy and half to three quarters the length of the spikelet (1.2-3 mm). Usually has fine hairs between the nerves and on the edges. Palea - Similar length to the lemma. Pointed tip. Lemma - Lower one as long as spikelet, 3 smooth nerves near each edge with midrib in centre. Fine, low lying silky hairs often with a frill of hairs. Upper (fertile) lemma almost the same size as the lower, pointed tip, smooth, hairless, oval to oblong. Stamens - Anthers -
Fibrous. Roots at the stem nodes.
Spikelets paired and all the way to the base of the 'fingers'. First glume is present. Sterile lemma is rough to touch on the nerves.
Annual. Flowers November to April. Germinates mainly in spring and makes rapid growth over the summer quickly covering the ground and competing with companion species.
It is a C4 plant, which makes it very competitive with C3 plants over summer and gives it tolerance to the triazine herbicides.
April in SA. Autumn to Summer in NSW. November to March in Perth. Summer in WA.
Seed Biology and Germination:
Population Dynamics and Dispersal:
Origin and History:
Cosmopolitan. Tropical areas. Central and South America.
ACT, NSW, NT, QLD, SA, VIC, WA.
Courtesy Australia's Virtual Herbarium.
Summer moist areas, irrigated areas.
Temperate to sub tropical.
Prefers summer moist soils.
Eaten by stock, but little forage value.
Serious weed of pineapples and orchards. Weed of cultivation, irrigated lucerne, rice, vegetables, vineyards, orchards, rotational crops, gardens, and lawns, recreational and disturbed areas.
Crab grass (Digitaria sanguinalis) is almost identical. Distinguished on flower characters. In summer grass the upper glume is 50-75% as long as lemma and the lower lemma is silky hairy, whilst in Crabgrass the upper glume is 30-50% as long as lemma and the lower lemma is rough to touch. In Summer grass the nerves on the upper lemma are scabrous at least in the upper part whereas in Crabgrass the are not. Crowsfoot grass (Eleusine indica) is similar but has hairless leaves, doesn't root at the nodes, has fewer flower heads and more than 2 florets per spikelet. Paspalum, Carpet grass, Barnyard grass, Millet, Pigeon grass, Kikuyu are similar.
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Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P217.
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P63.
Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P86.
Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P50. Photo.
Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
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Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P955.