Penstemon digitalis (Foxglove Beardtongue)

Penstemon digitalis, commonly known as foxglove beardtongue, is a remarkable perennial prized for its tubular white flowers and statuesque presence in the landscape. It is suitable for the perennial border, the natural landscape or prairie reconstructions.

Penstemon digitalis: An In-depth Look

Native: This plant is native to North America, particularly the eastern and southern United States.

Plant Type and Habit: This clump-forming, semi-evergreen perennial maintains an upright habit. Its stems are sturdy, supporting the tall, showy flower spikes.

Size: Typically, this species reaches heights of 3 to 5 feet (90-150 cm) and spreads approximately 2 feet (60 cm).

Flowers: The flowers are white to pale pink, two-lipped, and tubular, resembling those of foxgloves. They are arranged on panicles and make a striking display during blooming.

Bloom Time: Penstemon digitalis blooms from late spring to mid-summer, with the flowering period lasting several weeks. The flowers are followed by small capsules, which often turn reddish in late summer, dry brown in fall, and hold well into winter.

Foliage: The semi-evergreen foliage of Penstemon digitalis is deep green, with lance-shaped leaves arranged oppositely on the stem.

Uses: Penstemon digitalis is widely used in borders, native plant gardens, pollinator gardens, rain gardens, and naturalistic plantings, like meadows or prairie-style landscapes. Its tall, showy flowers make it popular for vertical visual interest. Good as cut flowers, too!

Pollinators: Penstemon is attractive to various pollinators, especially bees, and hummingbirds, drawn to their nectar-rich flowers. Additionally, its seeds provide food for songbirds in late summer and fall.

Toxicity: Penstemon digitalis has no significant toxicity issues for humans or animals, making it a safe addition to yards and gardens.

Deer and Rabbit: It’s generally resistant to deer and rabbits, though in areas of high foraging, no plant can be completely immune to being browsed.

Drought: Once established, it has moderate drought tolerance, though it prefers consistently moist soils. In particularly dry areas or periods, supplemental watering will enhance performance.

Invasiveness: While Penstemon digitalis self-seeds in optimal conditions, it’s not considered invasive and is often encouraged in native plantings for its ecological benefits.

Penstemon Growing Tips

Light: Full sun (at least 6 hours of direct sun per day). Tolerates light shade.

Soil: Fertile, well-drained loams, clay loam, sand soil. Avoid overly moist, poorly drained soils.

Water: Water well until plants are established. Once established, this Penstemon tolerates occasional drought and flooding. Allow the soil to dry out between waterings. Over-watering or wet soils can lead to root rot.

Fertilizer: Penstemon plants generally do not require heavy fertilization and can thrive in relatively lean soil conditions. However, providing them with a light application of an organic fertilizer in the fall can help boost their growth and flowering potential.

Pruning: Deadhead spent flowers to encourage continuous blooming. Cut back plants in late autumn or early spring to promote vigorous growth.

Mulching: Mulching Penstemon can help regulate ground temperature and suppress weed growth. Choose a mulch that does not hold water. Use organic materials like shredded bark, compost, or pine straw. Avoiding direct contact with the stems to prevent rot and pest issues.

Propagation: Propagate by seed in late winter or spring, softwood cuttings in early summer or semi-ripe cuttings in midsummer

Pests and Diseases: No serious pest or disease issues, but watch for slugs, snails, and nematodes. Fungal diseases can occur in overly wet conditions; ensure good air circulation and avoid overhead watering to prevent issues like powdery mildew, leaf spot, and root rot. Rust can cause small, rust-colored pustules on leaves and stems, leading to defoliation and stunted growth.