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Culture: Best grown in gritty, dry to medium, well-drained soils in full sun. Avoid moist, poorly-drained clay soils. Do not overwater. Full sun may help avoid onset of root rot. Plants may be cut back to basal foliage after bloom to improve appearance of the planting. May be grown from seed. Plants will self-seed in optimum growing conditions.
Noteworthy Characteristics: Penstemon grandiflorus, called large beard-tongue, is a prairie species that typically grows to 2-4’ tall. It is noted for its large, tubular, blue-lavender flowers and its hairless, broad-ovate leaves. Flowers (to 2” long) bloom in upright, open racemes in late spring. Foliage consists of thick, toothless, opposite, clasping, blue-green leaves, with the basal leaves obovate and the stem leaves rounded to elliptic. Although indigenous to Missouri, this species is only known to occur in grassy, open, loess hill areas in the far northwestern corner of the state. Genus name comes from the Greek words penta meaning five and stemon meaning stamen in reference to each flower having five stamens (four are fertile and one is sterile). Specific epithet means large-flowered.
Problems: Leaf spots, rusts and rots may occur. Plants tend to be short-lived. Some gardeners consider the plants to be inappropriate for conspicuous border areas because the bloom period is short and is followed by somewhat unattractive die back.
Uses: Meadows, open woodland areas, cottage gardens and native plant gardens. Effective when massed. Also may be used in borders.
All plant information courtesy of the Missouri Botanical Garden