[Erigeron bonariense L.; Conyza albida Willd. ex Spreng.; C. floribunda Kunth; Erigeron albidus (Willd. ex Spreng.) A. Gray]
(nat) Hairy horseweed, lani wela (Niihau)
Plants 1—10(—15) dm tall, often branched near base or unbranched, densely pubescent. Leaves numerous, usually grayish green, lower ones up to 15 cm long and 2 cm wide, becoming progressively smaller upward, usually 3-6 cm long and 0.5-1 cm wide, coarsely serrate. Heads usually numerous; involucre 4-6 mm high, densely pubescent; ray florets 50-200 or more per head, pistillate, rays ca. 0.5 mm long; pappus yellowish brown to reddish, in a single series, usually shorter than or equalling the inner florets. [2n = 18, 26, 32, 36, 54.] Perhaps native to South America but nearly cosmopolitan in distribution; in Hawaii a common weed in various urban and nonur- ban areas, generally in relatively dry habitats, sometimes in disturbed mesic to wet forest, on Kure Atoll, Midway Atoll, Lay- san, French Frigate Shoals, and all of the main islands. Naturalized prior to 1871 (Hillebrand, 1888).—Plate 20.
This species has been commonly confused with Conyza canadensis, but it can be separated using the characters given in the key.