Agriculture: Alfalfa Pest Management Guidelines

Winter Annual Weeds

The weeds shown here may be seen in fall-planted alfalfa seedlings. For weeds in spring-planted alfalfa seedlings, see common summer weeds. Names link to more information on identification and biology.

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Annual bluegrass (Poa annua): Grass family; winter annual; leaf tip shaped like bow of a boat; membranous ligule rounded with slightly pointed tip; leaf blade crinkled at midsection.	Burning nettle (Urtica urens): Nettle family; winter or summer annual; rounded seed leaves with smooth margin and small notch at tip; first true leaves with small notch at tip, opposite, stalked, and distinctly toothed.	Chickweed (Stellaria media): Pink family; winter annual; seed leaves with prominent midveins, about 4 times longer than wide, tapering to point at tip; true leaves broader, opposite, and yellow-green.
Common groundsel (Senecio vulgaris): Sunflower family; winter annual; seed leaves narrow, with blunt narrow tip; first true leaves with shallow teeth; third and fourth leaves more deeply lobed.	Common knotweed (Polygonum arenastrum): Seed leaves are long, very narrow, rounded at the tip and light green with a white cast. The true leaves are much broader, emerging from an encircling, membranous sheath at the leaf base.	Fiddlenecks (Amsinckia spp.): Borage family; winter annual; Y-shaped seed leaves with tiny blisters and a few fine hairs; early leaves with coarse, sharp hairs, and 4 to 6 times longer than wide.
London rocket (Sisymbrium irio): Mustard family; winter annual; seedlings narrow with long stalks; margins of first true leaves indented, distinguishing seedlings of London rocket from those of shepherd's purse; seedlings with deeply lobed leaves.	Little mallow (Cheeseweed) (Malva parviflora): Mallow family; winter annual; seed leaves heart shaped, sometimes with red tinge; true leaves roundish with wavy, shallow-toothed margins.	Mustards (Brassica spp.): Mustard family; winter annual; all mustard seedlings with broad seed leaves and deep notch at tip; first true leaves bright green on the upper surface and paler below.
Shepherd’s-purse (Capsella bursa-pastoris): Mustard family; winter annual; seed leaves pale green with tiny granules on surface; first true leaves with smooth margins; fourth and later leaves may be indented; true leaves covered with star-shaped hairs.	Wild oats (Avena fatua): Grass family; winter annual; first leaves with small marginal hairs and counterclockwise twist when viewed from above; ligule large, papery, and pointed.	Yellow starthistle (Centaurea solstitialis): Aster family; winter annual; seedlings are dull green; seed leaves are oblong, round at the tip, with smooth edges; first true leaves are longer and narrower with short, white hairs on the upper surface.

Text Updated: 11/06