Canadian horseweed (Erigeron canadensis)
Erigeron canadensis is an annual plant growing to 1.5 m (60 in) tall, with sparsely hairy stems. The leaves are unstalked, slender, 2?10 centimetres (0.79?3.94 in) long, and up to 1 cm (0.4 inches) across, with a coarsely toothed margin. They grow in an alternate spiral up the stem and the lower ones wither early. The flowers are produced in dense inflorescences 1 cm in diameter. Each individual flower has a ring of white or pale purple ray florets and a centre of yellow disc florets. The fruit is a cypsela tipped with dirty white down. E. canadensis can easily be confused with Conyza sumatrensis, which may grow to a height of 2 m, and the more hairy Erigeron bonariensis, which does not exceed 1 m (40 in). E. canadensis is distinguished by bracts that have a brownish inner surface and no red dot at the tip, and are free (or nearly free) of the hairs found on the bracts of the other species.