General:
Deciduous perennial from a long, creeping, underground rhizome.

Leaves:
Large, triangular, 3-pinnate, 60-170 cm long, 30-100 cm wide, with long, thick stipes, the ultimate segments numerous, woolly to smooth on the lower surface.

Notes:
Most BC plants of this species belong to P. aquilinum ssp. lanuginosum. Two subspecies can be distinguished as follows:

1. Leaves broadly triangular, but rarely divided in 3 main segments; pinnules nearly at right angles to the rachis, their lower surface densely woolly or woolly short-hairy; the inner indusium fringed and sometimes also hairy.................... ssp. lanuginosum (Bong.) Hult.

1. Leaves mostly with 3 main subdivisions; pinnules at an oblique angle to the rachis, their lower surface nearly smooth and short-hairy only on the midrib; the inner indusium without hairs......................... ssp. latiusculum (Desv.) C.N. Page

Source:  The Illustrated Flora of British Columbia