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Winter Annual Weeds

On this page
  • Annual bluegrass
  • Burning netttle
  • Chickweed
  • Common groundsel
  • Common knotweed
  • Fiddlenecks
  • Little mallow (Cheeseweed)
  • London rocket
  • Mustards
  • Sheperd's-purse
  • Wild oats
  • Yellow starthistle

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.

Click on photos to enlarge

Annual bluegrass
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
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.
(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
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.
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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.
(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
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
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.

(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.

Sheperd'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.

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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
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.

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