Yellow Penstemon in the Landscape
By: Stephen Love, University of Idaho
Scientfic Name: Penstemon confertusCommon Name: Yellow Penstemon
Description: Yellow penstemon is a long-lived, herbaceous perennial. It dies back annually to an above-ground woody stem. In spring, the plants develop large, dense basal mats of medium-sized, medium green, glossy leaves. From these mats arise upright to spreading flower stalks. Flowers grow in clusters (called verticillasters) along the stems. Flower color is yellow with a range of color intensity. Bloom period is early spring into summer. Yellow penstemon is found in seasonally moist meadows and can withstand more moisture than most other penstemon species. This plant is effective in rock gardens, beds, and borders.
Native Habitat: Penstemon confertus is native to the northern Rockies, Idaho, Montana, Oregon, Washington, and into Canada. Grows in seasonally moist forest edges and meadows at elevations ranging from 4,000 to 10,000 feet.
Cultural Requirement
Soil: Adapted to a range of soil types, including moist, but well-drained soils. Can tolerate soils with high levels of organic matter.
Moisture Tolerance: Can withstand more moisture than most other penstemon species. Although considered a drought-tolerant plant, supplemental irrigation will be beneficial.
Sun/Shade/Preference: Grows best in full sun but can tolerate some shade.
Transplanting: Tolerates transplanting well, both from pot to pot and from pot to garden. Plants develop rapidly and can be marketed in pots up to one gallon size.
Propagation: Easy to propagate from seed. Requires a 6 to 8 week cold stratification period to produce maximum levels of germination. Usually germinates in large numbers. Also, very easy to propagate using rooted cuttings.
Maintenance (pruning, fertilization, deadheading, division, irrigation, etc): Removing stems with spent flowers will keep the basal leaf mat healthy and may encourage some late-season bloom. Supplemental irrigation, applied at first signs of stress, is needed to extend bloom and keep leaves healthy. Only occasional, minimal fertilization is needed, as plants demand.
Insect, disease, or other problems: Yellow penstemon has no serious insect or disease problems.
Landscape Value
Use in the Landscape: Yellow penstemon is an upright, short- to moderately-tall plant with light to medium yellow flowers. Neutral flower color makes it easy to mix and match with other plants. It can be used in naturalized or formal rock gardens, beds, or borders. Yellow penstemon can also be successfully grown in decorative pots.
Weediness/Invasive Potential: Yellow penstemon is clump forming and vegetatively non-aggressive. It will occasionally produce volunteer seedlings, especially under moist soil conditions, but does not have an aggressively weedy habit.
Foliage: Leaves in the prominent basal mat are elliptical with a short petiole, bright green, thin, and glossy. Small, pointy, bract-like leaves are sparsely spaced up the flowering stalks to just below the flowers.
Flower: The flowers grow in tight clusters along upright stems that are 8 to 20 inches tall. The numerous tubular flowers are quite small, usually about ½ inches long. Flower color is yellow, but ranges in intensity from almost white to a pleasant medium yellow.
Timing: May-July
Fruit: A small, upright, globular capsule, with sharp, stiff lobes at the tip. Each capsule holds numerous seeds.
Form: Horizontal in pre-bloom phase, then upright to spreading when in flower.
Texture: Medium.
Ultimate Size: Plants from different locales vary in height. Generally 8 to 20 inches tall and 12 inches wide when mature.
Rate of Growth: Foliage establishes quickly and grows rapidly. Occasionally, some first-year bloom will occur. Full bloom potential is usually expressed the second and subsequent years.
Suggested Plant Partners: Yellow penstemon complements many other native plants and because it can withstand a wide range of conditions, is useful in many applications. Plant this species among trees and shrubs such as Pinus flexilis, Rhus trilobata, and Cornus sericea. Good wildflower partners include Zauschneria garrettii, Aquilegia coerulea, Aquilegia formosa, Monarda fistulosa, Erigeron compositus, Erigeron elatior, Linum lewisii, and other species of Penstemon.
Availability: Occasionally found as a potted plant at local or mail order native plant nurseries. Seed can be purchased from the American Penstemon Society or from native plant seed suppliers.
Cultivars: One dwarf cultivar named ‘Kittitas’ was released but is no longer in commerce.
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