Horeseweed, also called marestail, (Conyza canadensis) is an annual native plant, the seeds of which germinate in the spring and fall.
Erect 3 to 6 ft. tall, generally unbranched except at the top; leaves long and narrow with toothed margins, hairy, whorled around hairy stems
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