Wildflower/Perennial · Sonoran native
Rocky Mountain Penstemon
Penstemon strictus · Plantaginaceae
Also called: Rocky Mountain Beardtongue, Stiff Penstemon, Porch Penstemon
Rocky Mountain Penstemon (Penstemon strictus) is a low-water wildflower/perennial native to the Sonoran Desert region well suited to Tucson and the low desert. It thrives in full sun.
Rocky Mountain Penstemon at a glance
- Water use
- Low (established)
- Sun
- Full sun (light afternoon shade beneficial at low desert elevations)
- Mature size
- 18-30 in H x 18-30 in W (foliage mat ~12 in, flower stalks to ~30 in)
- Growth rate
- Moderate; evergreen basal mat, typically blooms in its second year
- Bloom
- Royal blue to deep violet-purple, tubular flowers, Late spring to early summer (roughly May-July; earlier in the low desert)
- Cold hardiness
- Very cold hardy, to about -20 to -30 F (USDA zones 4-9)
- Soil
- Light, dry, well-drained soils; tolerates poor and rocky ground. Needs sharp drainage and dislikes heavy clay.
- Native range
- Native to the Four Corners / southern Rocky Mountain region: northern Arizona, New Mexico, Utah, Colorado, Wyoming, and a bit of Nevada, at high elevations (~6,000-10,000 ft). Native to Arizona but NOT to the low Sonoran Desert.
- Best used as
- Hummingbird and pollinator gardens, Higher-elevation and transition-zone xeriscapes, Blue/purple spring color, Rock gardens
- Wildlife
- Attracts hummingbirds, bumblebees, and other native bees and beneficial pollinators.
- Toxicity
- Non-toxic.
How to grow Rocky Mountain Penstemon in Tucson & the low desert
Watering
Drought tolerant once established; adapted to higher, cooler elevations, so in Tucson's low desert give it well-drained soil, a cooler microclimate or afternoon shade, and water roughly weekly in the cool season, easing off in summer heat. It is the least heat-adapted of these penstemons for the low desert.
Fertilizer & nutrients
Low needs; thrives in lean soils. Little to no fertilizer required.
Pruning & care
Deadhead spent flower stalks after bloom to encourage rebloom and tidy the plant; leave the low evergreen foliage mat intact. Allow some seed set for reseeding.
Notes
A high-country / Colorado Plateau native (the most cold-hardy of this group) rather than a true low-desert plant. In Tucson it performs best in a cooler microclimate, at higher elevations around the city, or with afternoon shade and excellent drainage; in full low-desert heat it tends to be short-lived. Reliable reseeder.
Sources: Lady Bird Johnson Wildflower Center; Utah State University Extension Western Native Plants; High Country Gardens; University of Arizona Cooperative Extension (penstemon archives)