South Dakota Native Plant Research
Scrophulariaceae : Penstemon grandiflorus

Scrophulariaceae : Penstemon grandiflorus


Download Seed: The seeds of large beardtongue are brown and 2.5-4 mm long. (66 KB)

Download Seedling: One month old seedling grown in research greenhouse at SDSU. (77 KB)

Download Vegetative: The leaves of large beardtongue are entire and 3-16 mm long. (808 KB)

Download Mature plant (524 KB)

Download Flowering: Corolla (331 KB)

Download Flowering: calyx and inflated corolla (237 KB)

Download Fruiting: Capsules develop in mid to late summer and are 14-20 mm long. (466 KB)

Download Research garden: First seasons growth of beardtongue planted in research garden near SDSU. (82 KB)

Family Name


Common Name

Large-flowered beardtongue, Shell-leaf beardtongue

Native American Name

Lakota: kimímila tȟawánaȟča


Penstemon grandiflorus is a weakly perennial herb with 1-3 erect, smooth, waxy stems arising from a woody caudex growing up to about 1 m tall. The blue-green leaves are both basal and cauline, thick (succulent) and often covered in a waxy bloom, with entire margins. The basal and lower most stem leaves are shortly petiolate, spatula-shaped to orbicular, 3 to 16 cm long, 1-5 cm wide, rounded to pointed at the tip and tapering at the base. The sessile, opposite, ascending cauline leaves are 2- 9 cm long, 1.5-5 cm wide, more broadly egg-shaped, clasping at the base and reduced to bracts on the upper stem. The inflorescence consists of 3-9 clusters of flowers, with peduncles arising in the axils of the upper leaves, each cluster having 2-4 flowers on short pedicels. The green calyx has 5 lobes, 7-11 mm long. The bilabiate corolla is 35-48 mm long, abruptly inflated, lavender to bluish purple in color, the throat 15-18 mm wide, with magenta nectar guides on the inside. The lobes of the upper lip are spreading to reflexed, the lower lips spreading. The style and 4 stamens with black anthers hug the upper part of the tube and a white sterile stamen with a few yellow hairs on its tip is contained within the tube. The fruit is an ovoid capsule, 16-25 mm long containing several black to brown seeds up to 4 mm long. Large-flowered beardtongue blooms in May and June on prairies scattered throughout South Dakota.

Additional Notes

Shell-leaf beardtongue is the largest and most showy of the penstemons. Its foliage is eye-catching and its flowers striking. It blooms for a relatively short period and the plants live only 2-5 years. However, they do reseed themselves over time. These beardtongues are a great addition to a xeriscape or prairie garden and attract native bees, hummingbirds and butterflies.

Horticulture Notes

Seed collection: Fruit mature in June and July when they open and release the dark seeds.

Germination: Fall sowing into the garden is the first choice for planting. Spring planting when the ground is still cold or a 30-day cold moist stratification also provide good results.

Light: Full sun to partial shade.

Soil: Sandy to loamy well drained soils.

Water: Mesic to dry.

Scrophulariaceae : Penstemon grandiflorus