Rydberg's penstemon is an attractive penstemon with one to several erect to spreading stems rising from 20-40 cm high from a cluster of basal leaves. The herbage ranges from glabrous to covered with fine, short hairs, depending upon the variety. The basal leaves are often on short sterile shoots. They are oblanceolate tapering gradually to the petiole and 4-7 cm long and 9-15 mm wide. The upper stem leaves are lanceolate with sessile bases and range from 2.5-6 cm long and 3-14 mm wide.
The inflorescence consists of 2-7 densely flowered verticillasters. The calyx ranges from 3-7 mm long. The corolla is blue, blue-violet, or occasionally white and ranges from 10-16 mm long with the tube flaring gradually to the throat. The corolla lobes are roughly equal in length and the palate is white- to yellow-bearded. The anthers are glabrous outside, opposite, boat-shaped and splitting completely. The staminode rarely reaches the throat and is generally strongly bearded at the tip.
Variety aggregatus: Calyx mostly 5-8.5 mm long. Corolla 13-20 mm long. Plants covered with fine, short hairs. Plants found from southeastern Idaho to southwestern Wyoming and south to Utah and northern Arizona.
Variety oreocharis: Calyx 3-5 mm long, the sepals with thin, non-green, membranous edges, the margins irregularly but deeply toothed. Corolla 10-14 mm long. Plants glabrous throughout. Plants found from the Cascades of Oregon and Sierra Nevada of California east to northwestern Nevada.
Variety rydbergii: Calyx 3-6 mm long, the sepals with wide, non-green, membranous edges, the margins irregularly but shallowly toothed. Corolla 10-14 mm long. Plants with fine, short hairs or sometimes nearly glabrous. Plants of southeastern Washington and northeastern Oregon (and the Steens Mt.) east through central Idaho to southwest Montana.
Rydberg's penstemon may be found in moist meadows and moist open slopes from the foothills to moderate elevations in the mountains.
Rydberg's penstemon is found from central Washington south to the Columbia River where it extends towards the coast. It is then found southward through central Oregon (to the east of the Cascades) to northeastern California, and then eastwards to western Montana,Wyoming, Colorado, Utah and Nevada.