Penstemon, Genus, davidsonii, Species,
- Genus & species
Davidson's penstemon
Western North American mountain ranges (Cascades, Sierra Nevada)
Overview
Penstemon davidsonii is a low evergreen mat-forming subshrub reaching 2-6 inches (5-15 cm) tall in flower and 12-24 inches (30-60 cm) wide on woody prostrate stems that root where they contact gritty soil. Leaves opposite, leathery, oval to elliptic, 0.3-0.6 inch (8-15 mm) long, dark green with smooth or finely toothed margins, persisting through winter as bronze or purplish foliage. Flowers tubular-funnelform, lavender to deep blue-violet, 1-1.5 inches (2.5-3.8 cm) long, borne in short upright racemes of 2-8 flowers held just above the foliage from June through August. The corolla throat carries a hairy yellow staminode (sterile fifth stamen) that identifies Penstemon. Forms slow-growing patches 12-24 inches (30-60 cm) wide in 5-7 years. Plants do not survive in heavy soils that stay wet through winter and are short-lived (3-4 years) in low-elevation gardens with humid summers.
Native Range
Native to alpine and sub-alpine rocky ridges, scree slopes, and rock crevices in mountain ranges of western North America from southern British Columbia south through Washington, Oregon, and the Sierra Nevada to central California, generally at elevations of 4,000-12,000 feet (1,200-3,650 m).Suggested Uses
Used in rock gardens, troughs, scree plantings, and gravel terraces at 12-18 inch (30-45 cm) spacing in zones 4-7 cool-summer climates. Combines with Phlox diffusa, Eriogonum umbellatum, and other cushion alpines on west or south-facing rocky banks. Containers require sharply drained gritty mix in pots of at least 1 gallon (3.8 L); plants in moisture-retentive potting mix rot within one season.How to Identify
Appearance
Size & Dimensions
Height2" - 6"
Width/Spread1' - 2'
Bloom Information
June through August across the species range, with peak bloom in July at most sites. At highest elevations, bloom may begin in late July and end in early September. Individual flowers last 4-6 days; clumps produce sequential racemes over 4-6 weeks. Cool overcast summers extend bloom by 1-2 weeks.
Detailed Descriptions
Flower Description
Lavender to deep blue-violetFoliage Description
Dark green, leathery, bronzing in winterGrowing Conditions
Sun Requirements
Requires 6-12 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Establishes from container stock in 1-2 growing seasons in sharply drained gritty alpine soils with light watering through the first summer. Mature plants tolerate drought once established and rot quickly in irrigated garden soil or in potting mix that retains moisture. Crown rot is the leading cause of death in cultivation; planting on a slope or in a raised gravel bed prevents this. Foliage scorches in soils that warm above 80 degrees F (27 degrees C) without root cooling. Vine weevil larvae damage roots in container culture. Plants are short-lived (3-5 years) outside cool montane climates and benefit from periodic replacement from cuttings.Pruning
Cut spent flower stems at the base in late summer to neaten appearance and reduce self-seeding. Tip-prune unproductive woody stems by 1-2 inches (2.5-5 cm) in early spring to encourage new growth from the base. Plants respond poorly to hard pruning into old wood and rarely regenerate from cut woody stems.Pruning Schedule
Prune: March & August
early springsummer
Container Growing
Suitable for container growing
Minimum container size: 1 gallons
