penstemon

Penstemon (Penstemon digitalis)

Smooth Penstemon, Foxglove Beardtongue

Full to part sun, medium to slightly dry moisture, adapted to a wide range of soils including clay, moderately acid to neutral pH.

3–5 feet tall; blooms late spring to early summer (May–June in Middle Tennessee) with white tubular flowers on tall spikes; spreads by re-seeding and short rhizomes; blooms for a month or longer; one of the few penstemons that performs well in clay soil.

Germination Code: C(30), D, G. Spreads rapidly by re-seeding even from quite small seeds; striking planted in mass.

Native region: Scattered statewide in isolated counties in Tennessee; native to meadows, prairies, and open woodland edges.

Penstemon digitalis is the most adaptable penstemon for Middle Tennessee home landscapes, tolerating the clay soils and summer humidity that defeat most other penstemon species. The cultivar 'Husker Red' is widely sold and notable for its deep burgundy foliage, though it tends to revert to green in seedling offspring. Root rot occurs in wet, poorly drained soils — this is the primary failure mode; avoid planting in low spots. Attracts bumblebees, long-tongued bees, hummingbirds, and butterflies. Tolerates dry shade better than most penstemons, making it useful at the edge of tree canopies where clay and root competition limit other perennials.