Penstemon serrulatus

Common Names

Coast Penstemon, Serrulate Penstemon, Cascade Penstemon, Cascade Beardtongue, Serrulate Beardtongue, Cascades Penstemon

Summary

Penstemon serrulatus, Cascade penstemon or coast penstemon, is a semi-woody perennial herb native to the Pacific Northwest, from southern British Columbia to Oregon, west of the Cascade crest. It forms a branching, woody base with upright stems 20–70 cm tall and glossy opposite leaves with serrated margins; it bears broad, dense, one-sided clusters of deep blue to purple tubular flowers in midsummer.

It prefers gritty, sharply drained soil in full sun and tolerates a range of light conditions from full sun to partial shade with moist to wet soil; it is suited to cottage, informal, coastal, gravel, and wildlife gardens, borders, rock gardens, and raingardens, with flowering from June to August to attract pollinators. Propagation can be by softwood cuttings in spring, semi-hardwood cuttings in late summer, division in spring, or seed in fall, and deadheading after flowering prolongs bloom; winter protection with dry mulch is advised in colder areas; it may be susceptible to pests such as slugs, snails, aphids, and leaf eelworm, and to diseases such as grey mould, powdery mildews, and fungal leaf spot.

Lifecycle

Perennial

Height

8 inches to 2.5 feet tall

Spread

12-24 inches

Hardiness Zones

Zones 6a-9b

Sunlight Requirements

Ideally Full Sun, tolerates Partial Sun, Partial Shade, Full Shade.

Soil Type

Well-drained, evenly moist soil

Soil Drainage

Well-drained soil, evenly moist

Soil pH

Tolerates acidic, alkaline, or neutral soil pH

Bloom Color

Purple to deep purple-blue

Bloom Time

Summer

Foliage Color

Dark green, Green

Fall Foliage Color

Green

Leaf Lifecycle

Deciduous

Growth Rate

Medium growth rate (easy to grow), 2–5 years

Seasons of Interest

Summer

Propagation Methods

Seeds, Cuttings, Division

Attracts Wildlife

Attracts bees, butterflies, and other pollinators