Recently, my coworker exclaimed, “you can never have too many penstemons in your yard.”
I would agree.
Species of this genus display showy spikes of brightly-colored, bilateral flowers high above basal clumps of leaves. This is a diverse genus, however. Species range from herbaceous perennials to semi-shrubs, from 1-inch-tall cushion plants to plants with 4-foot-tall inflorescences. Leaves can be deciduous or evergreen. The floral color palette ranges from pale pink to scarlet, electric blue to grape juice purple, and snow white to almost yellow, attracting pollinators such as bumblebees and hummingbirds.
The center of diversity for this genus, and likely where it originated, is Utah. In fact, there are over 100 species of penstemon native to the arid and rocky beehive state. Colorado, with 65 taxa, may be the state with the second highest number of penstemon species. This means penstemon are adapted to the harsh climate of our region and, as a result, have gained popularity in landscaping. Many straight species and cultivars are available in the nursery trade. What follows are a few of my favorites.
Desert penstemon (Penstemon pseudospectabilis) is a long-lived species with spikes of pink flowers, which are a magnet for broad-tailed hummingbirds. Evergreen leaves provide winter interest.
Beardlip penstemon (P. barbatus) has brilliant reddish-orange, downward-pointing flowers, which are characteristics that attract hummingbirds. Deadhead this penstemon after its flowers fade, and you may be rewarded with a second bloom in the fall.
Rocky Mountain penstemon (P. strictus) is another long-lived, easy-to-grow penstemon that naturalizes with time. Flowers are bluish-purple and attract bumblebees.
Palmer’s penstemon (Penstemon palmeri) has tall spikes of large, pale pink, rose-scented flowers and blue green, evergreen leaves. Flowers attract very large bumblebees.
Large-flowered beardtongue (P. grandiflorus) has pink, blue-lavender or pale blue flowers. Perhaps a more precise common name would be “the largest-flowered beardtongue ever,” as flowers are almost exaggerated in size. This species often behaves as an annual or biennial but will seed around if allowed.
Pineleaf penstemon (P. pinifolius) is a diminutive species with linear evergreen leaves and red-orange tubular flowers. Mersea Yellow is a selection with yellow flowers and flowers of STEPPESUNS sunset glow are a warm orange.
SILVERTON bluemat penstemon (P. linarioides ssp. coloradoensis `P014S’) of Plant Select is another easy-to-grow small penstemon with silvery, evergreen leaves and lavender-blue flowers.
Bridges’ penstemon (P. rostriflorus) is a late bloomer that provides a final burst of red blooms in late-July through August.
Select a sunny, open site with well-draining soils. If needed, amend your soil with expanded shale or squeegee to improve drainage. Penstemons thrive in disturbed sites.
Mulch with pea gravel instead of wood chips.
Water deeply but infrequently.
Avoid synthetic fertilizers, or any fertilizer at all really.
Penstemons typically produce firecracker-like bursts of color from May through June and then are quiet for the rest of the season. To extend color and textural interest in your garden, select companion plants with similar water needs. My favorites include Artemisia, Agave, Hesperaloe, yarrow, blue flax, orange milkweed, chocolate flower, Colorado four o’clock and dwarf baby blue rabbitbrush.
Jen Toews is the plant recorder for the Denver Botanic Gardens
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