Xanthium strumarium var. canadense

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