Smooth beardtongue is a clump-forming perennial native to the eastern and central United States, with upright stems 24 to 36 inches tall topped with tubular lavender to pink-purple flowers through late spring and early summer. Bumblebees, hummingbirds and butterflies work the flowers, and the glossy green foliage is tidier than many native penstemons, which suits it to a formal border as well as a meadow planting.
It tolerates heavier clay better than most penstemons and asks little once established: full sun to part shade, soil that drains, 12 to 18 inches apart, and water through the first season. Deadhead the spent spikes for a tidier plant, or leave a few standing for the seed heads, which hold through winter. It self-sows modestly and is easy from seed sown in fall. Divide in spring every few years.
The flowers are a landing platform for long-tongued bees, and the plant is a host for the caterpillars of several checkerspot butterflies. Deer and rabbits leave it alone. It pairs well with golden alexanders, wild bergamot and little bluestem in a native border. Hardy in zones 4 to 8.
Ecoregions:Northern ForestsEastern Temperate Forests
Powdery mildew
White or grey powdery coating on leaves - usually starting on older growth in humid conditions or when nights cool.
Improve air circulation by thinning plants. Apply neem oil or potassium bicarbonate spray at first sign. Avoid overhead watering.
Crown Rot
Lower leaves yellow and wilt; the base of the rosette turns brown and soft, sometimes with white fungal threads at the soil line. Plants collapse in wet conditions.
Remove and destroy affected plants. Improve drainage and avoid overhead watering. Do not mulch directly against the crown. Space plants for airflow and avoid replanting in the same wet spot.
Fungal leaf spot
Brown or purplish spots on the leaves, often ringed with a yellow halo, that spread and merge in warm, humid, or wet weather; heavily spotted leaves yellow and drop early.
Pick off spotted leaves and clear fallen debris to remove overwintering spores. Improve air circulation by thinning, and water at the base so foliage dries quickly. If it persists, apply a copper- or sulfur-based fungicide at the first sign.