E-Flora BC: Electronic Atlas of the Flora of British Columbia

General:
Dioecious tree up to 20 m tall; not colonial; branches yellowish-brown to grey; twigs yellowish, smooth.

Leaves:
Alternate, deciduous, simple, triangular, 4-10 cm long, 4-11 cm wide, the bases heart-shaped or squared-off, smooth, finely toothed and hairy, the teeth often callous-tipped, both sides green; leaf stalks 4-14 cm long, often with a pair of glands near the blade; buds finely hairy with fringed scales, resinous.

Flowers:
Borne in catkins; male catkins 5-9 cm long, soon deciduous, with 40-60 stamens; female catkins 8-15 cm long.

Fruits:
Capsules, egg-shaped, carpels 3-4, smooth, short-stalked.

Notes:
Two subspecies apparently occur in BC:

1. Winter buds smooth; emerging leaves long-hairy; flower stalks variable in length ....................ssp. Deltoides

1. Winter buds pubescent; emerging leaves smooth; flower stalks uniform in length (less than 6 mm long)..................... ssp. monilifera (W. Aiton) Eckenwalder