Smooth beardtongue is a clump-forming perennial native to the eastern and central United States — the upright stems topped with tubular lavender to pinkish-purple flowers are highly attractive to bees, hummingbirds, and butterflies through late spring and early summer. The glossy green foliage is tidier than many native penstemon species, making it a good fit for more formal borders as well as naturalistic plantings.
Valued for its adaptability, it tolerates heavier clay soils better than most penstemons, and once established asks little in return. Deadhead spent spikes to encourage tidy growth, and leave a few standing for the architectural seed heads that follow.
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.