University of Maryland Extension



Horseweed or Marestail
Conyza canadensis


Life cycle: annual, germinating in fall or spring
Growth habit: erect 3 to 6 ft. tall, generally unbranched except at top; leaves long and narrow with toothed margins, hairy, whorled around hairy stems
Reproduction: seeds spread by wind; many small, white ray and yellow disk flowers
Conditions that favor growth: primarily a weed of nursery crops and orchards, perennial crops, waste areas and fallow fields
Cultural control: manual cultivation (it is very easy to pull) or maintain regular mowing to prevent flowers and seed production. It has been documented that horseweed is resistant to glyphosate a common ingredient in non-selective herbicides. 


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