Rocky Mountain Penstemon (Strictus)

The Rocky Mountain Penstemon (Strictus) is generally described as a perennial forb/herb. This is native to the U.S. (United States) has its most active growth period in the spring and summer . The greatest bloom is usually observed in the late spring, with fruit and seed production starting in the spring and continuing until summer. Leaves are not retained year to year. The Rocky Mountain Penstemon (Strictus) has a moderate life span relative to most other plant species and a moderate growth rate. At maturity, the typical Rocky Mountain Penstemon (Strictus) will reach up to 2 feet high, with a maximum height at 20 years of 0 inches.

The Rocky Mountain Penstemon (Strictus) is easily found in nurseries, garden stores and other plant dealers and distributors. It can be propagated by seed. It has a slow ability to spread through seed production and the seedlings have low vigor. Note that cold stratification is not required for seed germination and the plant cannot survive exposure to temperatures below -33°F. has medium tolerance to drought and restricted water conditions.

Uses of : Landscaping, Medicinal, Culinary, etc.

Grazing/rangeland: 'Cedar' Palmer’s penstemon (Penstemon palmeri) and 'Bandera' Rocky Mountain penstemon (Penstemon strictus) are the only released penstemons noted to have any forage value. All other varieties are considered fair to poor palatability and considered to be only incidental forage value. All species provide diversity to the seeded plant community.

Erosion control/reclamation: All species are mentioned for their value in mixes for erosion control and beautification values.

Wildlife: Penstemons are considered desirable forages for deer, antelope, and birds either as herbage or seed. They may also provide some cover for selected small bird species. They provide diversity to the plant community.

General Characteristics

General: Figwort Family (Scrophulariaceae). Penstemon or beardtongue species are perennial forbs or sub-shrubs to shrubs with attractive flowers. They are short to long-lived. Penstemons have opposite, entire, or toothed leaves. They have several stalked flowers or flower clusters that are borne in the axils of the upper leaves or leaflike bracts. The tubular corolla is strongly to distinctly two-lipped at the mouth with a two-lobbed upper lip and a three-lobbed lower lip. There are 4 anther-bearing (fertile) stamens and a single sterile stamen or staminodia that is often hairy at the tip. The fruit is a many-seeded capsule.

Penstemon strictus is a perennial herb growing 12 to 36 in tall. It has one to few stems arising from a thick crown. The leaves are entire and narrowly oblanceolate. The flowers are deep blue with parts of the corolla violet and whitish. The staminode is sparsely bearded to glabrous. This species likes full sun to partial shade, well drained soils, and blooms in the summer. A good line drawing and identification key is available in Cronquist et al. (1984).

Required Growing Conditions

This species is found in the southern Rockies. Except for one minor species, the genus Penstemon does not occur naturally outside of North America. For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.

Cultivation and Care

Adaptation: Penstemons do best on well-drained soils. Most ecotypes do well on infertile, disturbed soils. They have excellent cold winter and drought tolerance. They will tolerate weakly saline to weakly acidic sites. They are usually found in open areas, but will tolerate semi-shaded conditions. They are not tolerant of fire, but are fire resistant due to leaves staying green with relatively high moisture content during the fire season.

Rocky Mountain penstemon is often associated with sagebrush in pinyon-juniper woodland, oak scrub, and openings of ponderosa pine and spruce-aspen forest from 2200 to 3200 m in elevation (Cronquist et al. 1984).

Planting: These species should be seeded with a drill or broadcast at a depth of 1/4 inch or less into a firm seedbed. Ideal seeding depth is 1/8 inch. Penstemons are not recommended for single species seeding. The full seeding rate (not recommended) for these forbs-shrubs is 1.5 to 3 pounds Pure Live Seed (PLS) per acre or 20 to 26 PLS per square foot (varies somewhat by species). Some recommend 4 lbs PLS per acre for Rocky Mountain penstemon. There are an estimated 478,000 seeds per pound for this species. When used as a component of a mix, adjust to percent of mix desired. For mined lands and other harsh critical areas, doubling the seeding rate component of penstemon is not required.

The best seeding results are obtained from seeding in very early spring (because of grass component of mix) on heavy to medium textured soils and in late fall on medium to light textured soils. Late summer (August - mid September) seeding is not recommended. Dormant fall seedings (preferred seeding period for penstemons) will pre-chill seed and reduce seed dormancy which is very strong in some species. Mulching, irrigation, and weed control all benefit stand establishment. Seedling vigor is good, but not as good as most grasses. Germination may not occur until the second growing season. Flowering should not be expected until at least the second growing season.

Stands may require weed control measures during establishment. Because penstemons are broadleaf, use of 2,4-D is not recommended. Mow weeds at or prior to their bloom stage. Grasshoppers and other insects may also damage new stands and pesticides may be needed.

General Upkeep and Control

Growth of penstemons begins in early spring and flowers appear in May through July depending on species. Weed control and removal of very competitive species may improve chance of establishment. Damage from wildlife and rodents may occur and they may need to be controlled. Disease problems are minimal except under irrigation. Under irrigation fusarium wilt can be a problem.

Environmental Concerns: Penstemon species establish and spread slowly via seed distribution. They are not considered weedy or invasive species, but can spread into adjoining vegetative communities under ideal climatic and environmental conditions. They coexist with other native species and add biodiversity to those plant communities.

Seed Production Penstemons should be seeded in at least 36-inch rows at the rate of 2.5 pounds PLS per acre to allow mechanical weed control. The use of weed barrier material may be an alternative to allow closer spacing. They should be seeded in late fall or early winter unless seed is stratified under cool moist conditions. The Clearwater Selection of alpine penstemon does not require stratification. Transplants by dividing the base of older plants or from greenhouse starts can also be successfully used to establish seed fields.

Seed is generally harvested by hand stripping or by combine. Seed is mature when capsules are dry and seed is hard and dark in color. Flowering is indeterminate with mature capsules and flowers present at harvest period. Multiple harvest periods (by hand) may be necessary to maximize seed collection. Some seed will shatter once capsules open, but the capsule is upright and tends to hold seed very well. Seed can be separated from the capsule by use of a hammer mill or barley de-bearder followed by air screening. Cleaned seed should be allowed to dry and then stored in a cool dry area. An after-ripening period of 3 to 4 months is required. Seed retains viability for several years under these conditions.

Plant Basics
Growth Rate Moderate
General Type Forb/herb
Growth Period Spring, Summer
Growth Duration Perennial
Lifespan Moderate
Plant Nativity Native to U.S.
Commercial Availability Routinely Available
Physical Characteristics
Bloom Period Late Spring
Displays Fall Colors Yes
Shape/Growth Form Stoloniferous
Drought Tolerance Medium
Shade Tolerance Intolerant
Height When Mature 2
Vegetative Spread Moderate
Flower Color Purple
Flower Conspicuousness No
Fruit/Seed Abundance Medium
Fruit/Seed Seasonality Spring Summer
Seed Spread Rate Slow
Gardening Characteristics
Propagations (Ways to Grow) Seed
Moisture Requirements Low
Cold Stratification Required No
Minimum Temperature -33
Soil Depth for Roots 10
Toxic to Nearby Plants No
Toxic to Livestock No
After-Harvest Regrowth Rate Slow
After-Harvest Resprout Ability No
Responds to Coppicing No
Growth Requirements
pH Range 6–8 pH
Precipitation Range 14–14 inches/yr
Planting Density 0–0 indiv./acre
Soil Textures Coarse
Soil Depth for Roots 10
Minimum Frost-Free Days 120 day(s)
Salinity Tolerance None
CaCO3 Tolerance Low
Sustainability & Use
Leaf Retention No
Palatability Medium
Fire Resistant No
Causes Livestock Bloating None

Source: USDA, NRCS, PLANTS Database,
National Plant Data Center, Baton Rouge, LA 70874-4490 USA