IPMP3.0, Oregon State University, Copyright 2000

Biology and Management of Horseweed


Registered Herbicides

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  General Description:

Horesweed is an annual that reproduces by seed. Young plants form a rosette with softly toothed and hairy leaves. Mature plants produce a 2- to 5-foot stem that is terminally brached. Stems are stout, erect, unbranched at the base with bristly hairs. Flower heads are numerous, small, in axillary panicles.  Numerous small, white or pink flowers are produced on stem branches. Seeds are 1/16 inch long with numerous slender white bristles on one end.

Herbicide Control Notes:

  • Gramoxone plus Karmex/Direx more effective than either herbicide alone.