Asteraceae : Conyza canadensis

Conyza canadensis is an annual, herbaceous plant growing from 0.3 10 to 1.5 m tall, mostly simple or branching above if injured, with sparsely hairy stems. The simple, alternate leaves are sessile, narrowly oblanceolate to linear 2–10 cm long and generally < 1 cm wide, with entire to coarsely toothed margins. The leaves grow in a spiral up the stem and the lower ones often wither early. The inflorescence is a terminal cluster of flower heads 1 cm in diameter, with an involucre, of overlapping bracts, that is 3-4 mm long and green. Twenty to 30 ray flowers with white to pale purple ligules and a few yellow disc florets in the center. The fruit are hairy achenes with an abundant pappus. Horseweed is a weed in open cultivated and disturbed ground flowering from June through September throughout South Dakota.