Reproducing only by seed.
5 - 120 cm (2 in. - 4 ft) long, erect, spreading, or lying on the ground and rooting at nodes (a) in contact with the soil.
Leaves numerous near the base of the plant and scattered along the stems, 4 - 20 cm long, 5 - 10 mm wide and gradually tapered towards the pointed tip; leaf blades and leaf sheaths sparsely to densely soft-hairy; the hair (b) standing more or less straight out; leaf sheaths split, the margins (c) hairless and overlapping; ligule (d) membranous, 0.5 - 2 mm long; no auricles
Inflorescence finger-like, with several thin, slender, spikes (e) in a whorl at the top of the stem (A), or more usually with 2 or 3 sets of branches from the upper 2 - 4 cm of stem; each spike (â€œfingerâ€) flattened and with the single-seeded spikelets (f) closely arranged along only one side (C, D); seeds purplish-green and ridged lengthwise. Flowers from July to September.
Fibrous root systems.
Both kinds of crab grass are common in southern Ontario but they also occur sporadically in northern and northwestern Ontario. Both occur in row crops and other fields, waste places, gardens and lawns.
Corn yield loss (%)*: 1 % at 1 plant/m2 3 % at 5 plant/m2 Soybean yield loss (%)*: 1 % at 1 plant/m2 3 % at 5 plant/m2 *assumes that the weed has emerged with the crop and has been left uncontrolled all season.
Before heading out, they are distinguished by their tapered leaf blades, their split sheaths with hairless margins (c), their membranous ligules (d, g) with no auricles, their more or less hairy lower leaf sheaths (b), and their either hairy or smooth blades. After heading out, the slender finger-like spikes are distinctive.
Large crab grass is not known to be toxic.
Large crabgrass is not a known allergen.
No information exists at this time.
No information available at this time.
Smooth crabgrass (DIGIS), Proso millet (PANMI), Witch grass (PANCA)
Currently none available for this weed. Visit http://res2.agr.ca/Lethbridge/weedbio/index_e.htm#toc for the latest research on biological weed control.
Currently none available for this weed in corn and soybean. Corn gluten meal will inhibit germination of crabgrass seeds in turf.
No documented cases of herbicide resistance to date. For more information on weed resistance: http://www.plant.uoguelph.ca/resistant-weeds/
[b]Large crab grass: A. Plant. B. Leaf base. C. Side view. D. Back view of a portion of spike with several spikelets.[/b] Smooth crab grass: E. Leaf-base of lower leaf.
Leaf blade: Hairy on both sides.
Leaf sheath: Hairy, yet the margins are hairless.