Penstemon cardwellii
Cardwell's penstemon
Overview
A low evergreen subshrub reaching 6-12 inches (15-30 cm) tall and 18-36 inches (45-90 cm) wide, forming a dense mat from a woody base with prostrate to ascending stems. Leaves opposite, evergreen, oblong to elliptic, 0.5-1.5 inches (1.5-4 cm) long, dark green, often turning bronze-purple in winter, with smooth to finely toothed margins. Inflorescences short terminal racemes of 3-12 tubular flowers held just above the foliage. Each flower 1-1.5 inches (2.5-4 cm) long, deep purple to violet-blue with a paler throat marked by white guidelines, two-lipped. Sterile staminode bearded with yellow hairs. Capsules 0.25-0.4 inch (6-10 mm), ripening in summer. Plants spread by stem-rooting where lower branches contact moist soil and form clonal patches up to 4 feet (120 cm) wide after 8-10 years. Foliage often turns bronze-purple under winter cold; new growth resumes in spring.
Native Range
Native to the Cascade Range and Coast Ranges of southwestern Washington and western Oregon south to northern California. Found on rocky slopes, gravelly road cuts, and open coniferous forest from 1,500 to 7,500 feet (460-2,290 m) elevation, often on volcanic or pumice-rich soils.Suggested Uses
Commonly planted in rock gardens, dry stone walls, and slope plantings at 24-36 inch (60-90 cm) spacing. Suitable for containers of at least 3 gallons (11 L) with at least 50% mineral grit. Pairs in cultivation with other dry-site Pacific Northwest natives such as Eriogonum umbellatum and Arctostaphylos uva-ursi.How to Identify
Appearance
Size & Dimensions
Height6" - 1'
Width/Spread1'6" - 3'
Reaches mature size in approximately 4 years
Bloom Information
Detailed Descriptions
Flower Description
deep purple to violet-blueFoliage Description
dark green, bronze-purple 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
Plant container-grown specimens in autumn or early spring into sharply draining gritty soil. Water weekly during the first growing season; established plants tolerate periods of 4-6 weeks without rain. Soils that retain moisture at the woody crown cause root rot within one season. Plants establish slowly and may not flower until year 2 or 3 from young plants. Cuttings root in 4-6 weeks in late summer and are the typical propagation method. Plants persist 8-15 years in suitable rocky sites with sharp drainage.Pruning
Cut spent flower stems to the topmost set of leaves after flowering. Light shaping can be done in early spring; old wood does not regrow when cut hard, so removal is limited to no more than one-third of stem length per year. Damaged stems can be removed at the woody base at any time.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
summerearly spring
Container Growing
✓ Suitable for container growing
Minimum container size: 3 gallons