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Marestail/horseweed (Conyza canandensis) is becoming more commonly glyphosate-resistant. Seed that germinates throughout spring and early summer will mature and set seed the same year, while seed that germinates in fall overwinters in the rosette stage. Plants reach heights of 3 to 6 feet, and one plant may release 200,000 seeds that disperse easily by the wind.

Marestail foliage (Videki, Coronicum Kft,
Marestail foliage.

(Photo: Robert Videki, Doronicum Kft,

Marestail flowers (Harte,
Marestail flowers.

(Photo: Mary Ellen (Mel) Harte,



  • Pre-emergent herbicides
  • Burn-down herbicides during seedling or rosette stages


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