The leaves provide the best way to distinguish hydrophyllum occidentale
from similar species such as hydrophyllum fendleri
; they are pinnately divided into an odd number (7 to 15) of leaflets, which have a relatively small number (2 to 4) of large, rounded teeth along the edges. Leaflet tips are also rounded, rather than pointed. The uppermost three leaflets are merged at the base; not completely divided. Stems have quite a dense covering of long, bristly white hairs, as do the leaf-like sepals beneath the flowers.
The inflorescence is held well above the ground; a compact, spherical cluster atop a reddish-green, leafless stalk, generally higher than the uppermost leaves. Individual flowers are bell-shaped, formed of five white to lavender-colored petals, a split style and five purple stamens, each attached to the midpoint of a red-brown anther. Style and stamens are exserted well beyond the petals.