Penstemon 'Sour Grapes' is a compact hybrid beardtongue producing tubular flowers in a dusky grape-purple with lavender overtones from late spring through summer. It performs well in dry, sunny borders and gravel gardens where sharp drainage and lean soil suit it best.
Penstemons are naturally short-lived perennials that persist longest in low-fertility, well-drained conditions. Rich or consistently moist soil shortens lifespan and promotes crown rot. A moderate cut-back after the main flush of growth can encourage a second period of stems. In zones 9–10 the plant behaves as a semi-evergreen sub-shrub; at the cooler end of its range (zone 7), mulching the crown before hard freezes improves winter survival. Soil pH in the neutral to slightly alkaline range suits it well.
The tubular flower shape is well matched to hummingbirds and long-tongued bumblebees, making this cultivar a reliable nectar source in summer pollinator plantings.
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.
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.
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.