It’s easy to see why penstemons are so popular with gardeners everywhere. Their tubular or trumpet-shaped flowers, usually on tall spikes, put on a brilliant show from late spring until fall. Flower color ranges from shades of purple to red, blue, white, yellow, or pink, often with contrasting markings at the base. Hummingbirds and butterflies are drawn to them.
Some penstemons are tall and upright, excellent in the mixed border; others are low mats perfect for the rock garden; and still others are sprawling mid-size mounds. All need good to excellent drainage, but their needs for water vary widely.
There are penstemons native to sunny dry situations, and these are good candidates for gardens in summer-dry climates. Foothill penstemon (Penstemon heterophyllus) is stunning in full bloom, its flowers a pure blue to gentian blue-violet with a spot of pinkish purple at the base. The deep green to bluish green leaves are narrowly linear. Out of bloom, in small nursery pots, this lovely native may be passed over in favor of taller, broader-leaved “border” penstemons except by native plant enthusiasts who know what they’re looking for.
A clump-forming perennial, a foot tall and twice as wide with masses of flowers on two-foot stalks, foothill penstemon is native to dry hillsides in California’s coast ranges. Long-lived and undemanding, it needs excellent drainage and a warm sunny location. An occasional soaking in summer is appreciated but not necessary, and light afternoon shade may be best in hot inland locations. Spent flowers can be removed to extend bloom.
A highly variable plant, several named varieties are offered. ‘Margarita BOP’ is more tolerant of regular garden conditions and ‘Walker Ridge’ is a shrubby groundcover. ‘Margarita BOP’ is stunning spilling over a wall or the edges of a large container.
There are other good penstemons for summer-dry climates. Penstemon campanulatus, native to Mexico, is a prolific bloomer with lavender and white flowers requiring no summer water. P. centranthifolius, native to central and southwestern California, has brilliant red flowers and gray-green leaves. P. clevelandii, with pink flowers and gray-green foliage, is found in the inner coast ranges and the edges of the desert in southern California and northern Baja California. P. spectabilis is a tall perennial native to coastal bluffs of southern California. It has lavender flowers and green or grayish green leaves.