General:
Annual herb from a taproot; stems erect, solitary, simple, stiff-hairy or nearly glabrous, 0.2-2 m tall.

Leaves:
Basal leaves lacking; stem leaves broadly egg-shaped to kidney-shaped, becoming heart-shaped at the base, alternate, sometimes shallowly 3- to 6-lobed, stalked, 2-15 cm long including the stalks, stiff-hairy or nearly glabrous.

Flowers:
Heads unisexual in several or many short, axillary clusters; male involucres of separate bracts, female involucres of fused bracts forming a conspicuous cylindric to egg-shaped 2-chambered bur with hooked prickles, 1-3.5 cm long; corolla lacking.

Fruits:
Achenes thick, solitary in the chambers of the bur; pappus lacking.

Source:  The Illustrated Flora of British Columbia

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:
Xanthium acerosum Greene
Xanthium californicum Greene
Xanthium californicum var. rotundifolium Widder
Xanthium campestre Greene
Xanthium canadense Mill.
Xanthium cavanillesii Schouw
Xanthium cenchroides Millsp. & Sherff
Xanthium commune Britt.
Xanthium echinatum Murr.
Xanthium glanduliferum Greene
Xanthium italicum Moretti
Xanthium macounii Britt.
Xanthium oligacanthum Piper
Xanthium oviforme Wallr.
Xanthium pensylvanicum Wallr.
Xanthium saccharatum Wallr.
Xanthium speciosum Kearney
Xanthium strumarium subsp. italicum (Moretti) D. L÷ve
Xanthium strumarium var. oviforme (Wallr.) M.E. Peck
Xanthium strumarium var. pensylvanicum (Wallr.) M.E. Peck
Xanthium varians Greene