Perennial herb from a taproot or woody stem-base; stems erect, simple or several, branched, glabrous below, fine-hairy above, 30-80 cm tall.
Basal leaves lacking; stem leaves egg-shaped to oblong in outline, alternate, stalked, 1-2 times pinnately cut, 4-10 cm long, 1-6 cm wide, coarsely rounded or pointed at the tips, finely hairy, at least beneath.
Heads with ray and disk flowers, several, terminal on the branches in a short, flat- to round-topped inflorescence; involucres 2-3 mm tall; involucral bracts lanceolate, in 2-3 series, keeled, leathery, sparsely hairy with a narrow translucent margin; ray flowers white, mostly 15-30, 1-2 cm long; disk flowers yellow, 2-3 mm long, somewhat glandular below.
Achenes squared off at the top, cylindric or nearly so, 8- to 10-nerved; pappus lacking or a minute crown.
If more than one illustration is available for a species (e.g., separate illustrations were provided for two subspecies) then links to the separate images will be provided below. Note that individual subspecies or varietal illustrations are not always available.
Illustration Source: The Illustrated Flora of British Columbia
Synonyms and Alternate Names:
Chrysanthemum parthenium (L.) Bernh.
Matricaria parthenium L.
1. Heads disciform, numerous, usually 20-200.......................T. vulgare
1. Heads with ray and disk flowers, few to many, usually less than 20
2. Rays flowers white; leaves once or twice pinnately divided, the relatively broad segments often overlapping.......................T. parthenium
2. Rays flowers yellow; leaves twice to three times pinnately divided, the segments not at all overlapping........................T. bipinnatum
Source: Illustrated Flora of British Columbia