Shrubby penstemon is a woody, mat forming penstemon with numerous flowering and sterile stems atop dense mats of leaves. The flowering stems may reach a height of 40 cm and are freely branched.
The leaves are evergreen, leathery, and shiny green. The leaves are both basal and cauline (stem), with the latter being smaller. In variety fruticosus, the leaves are up to 6 cm long with entire or finely toothed margins.
The inflorescence is a few-flowered raceme. The glandular sepals are pointed at the tip. The corolla is blue-lavender to purple, and up to 5 cm in length. The palate is bearded and white or yellowish in color. The flowers are tubular with two spreading lips. The lower lip is longer than the upper. The calyx is glandular with entire-margined, leafy sepals from 7-15 mm long. The anther sacs are densely white and woolly. The staminode is yellow-bearded at the narrow tip and about one-half the length of the filaments.
Variety fruticosus: Leaf blades up to 6 cm long, usually 2-7 times longer than wide. Plants found from southern British Columbia south to the east of the Cascades in central Washington to the Columbia River Gorge and east across central Idaho to Montana, and Wyoming.
Variety scouleri: Leaf blades 2-5 cm long with mostly entire margins. Leaves linear in shape, mostly 6-10 times longer than wide. Plants of southeastern British Columbia, northeastern Washington, and northern Idaho.
Variety serratus: Leaf blades mostly 1-2.5 cm long with sharply toothed margins. Plants of southeastern Washington, northeastern Oregon and west-central Idaho.
Shrubby penstemon inhabits rocky, often talus slopes to forests, from the foothills into alpine areas.
Shrubby penstemon is found east of the Cascade summit from British Columbia, south through the Washington Cascades, and eastward to the Idaho panhandle, and again eastward to Wyoming. A southern branch extends through central Oregon to the Cascades, and also down the Columbia Gorge.