Penstemon serrulatus
coast penstemon
Overview
Penstemon serrulatus is an herbaceous perennial reaching 12-30 inches (30-75 cm) tall and 12-18 inches (30-45 cm) wide on upright unbranched stems from a basal mat of foliage. Leaves opposite, lance-shaped to ovate-lance-shaped, 1.5-3 inches (4-7.5 cm) long, dark green and shiny with sharply serrated margins (the species epithet serrulatus spp. refers to these small saw-toothed edges). Stem leaves sessile and clasping. Flowers tubular-funnelform, deep blue to violet-purple (occasionally white), 0.75-1.25 inches (19-32 mm) long, with a bearded yellow staminode in the throat, borne in dense whorled or one-sided terminal clusters from June through August. Forms slow-spreading clumps from short rhizomes, reaching 18-24 inches (45-60 cm) wide in 4-5 years. Tolerates wetter sites than most Penstemon spp., including stream margins and meadow edges that retain summer moisture.
Native Range
Native to coastal forests, streambanks, moist meadows, and forest edges in the Pacific Northwest from southern British Columbia south through western Washington and the western Cascades to northern California, primarily west of the Cascade crest at elevations from sea level to 5,500 feet (1,675 m).Suggested Uses
Planted in moist meadow gardens, native plant gardens, and stream margins at 18-24 inch (45-60 cm) spacing in zones 6-9. Combines with Camassia leichtlinii, Mertensia platyphylla, and other PNW moist-meadow species in restored riparian plantings. Grows in containers of at least 3 gallons (11 L) with a moisture-retentive humus-rich potting mix; plants in sharply drained mixes dry out and decline rapidly in summer.How to Identify
Appearance
Size & Dimensions
Height1' - 2'6"
Width/Spread1' - 1'6"
Reaches mature size in approximately 3 years
Bloom Information
June through August across the species range, with peak bloom in late June through July. In zones 8-9 along the coast, bloom may begin in late May. Individual flower clusters open over 2-3 weeks; total stand bloom lasts 5-7 weeks. Cool overcast summers extend bloom by 1-2 weeks.
Detailed Descriptions
Flower Description
Deep blue to violet-purple, rarely whiteFoliage Description
Dark green, shiny, sharply serratedGrowing Conditions
Sun Requirements
Requires 4-8 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 or direct-sown seed within one growing season in moist humus-rich soils with weekly water through the first summer. Mature plants tolerate periodic drought but require more consistent moisture than other PNW Penstemon spp. species; bloom and longevity decrease in dry summers without supplemental water in zones 7-9 east-side gardens. Crown rot occurs in heavy clay soils with poor drainage. Plants are short-lived (4-6 years) but reseed readily where soil is undisturbed; volunteer seedlings appear at 5-15 per parent plant per year. Powdery mildew may affect lower leaves in late summer in still-air sites.Pruning
Cut spent flower stems at the base in late summer after seed has set or earlier to extend bloom into a second flush. Tattered or browned outer leaves are removed in early spring before new growth emerges. Plants respond poorly to cutback during the growing season and may decline if mid-season hard pruning is applied.Pruning Schedule
J
F
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A
M
J
J
A
S
O
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early springsummer
Container Growing
✓ Suitable for container growing
Minimum container size: 3 gallons