Penstemon 'Sour Grapes'

Penstemon 'Sour Grapes'

Elegant spikes of small, tubular, foxglove-like flowers appear from July to October among lance-shaped, bright green leaves. The magenta-blue flowers of this penstemon have a metallic sheen, reminiscent of black grapes, which contrasts particularly well with deep purples and blues.

Find this penstemon among agapanthus and salvias alongside the Canal area at Wisley. The penstemons here flower for months, often surrounded by bees buzzing in and out of their tubular flowers.

Vital statistics

Common name

Penstemon 'Sour Grapes'

Family

Plantaginaceae

Height & spread

60 x 45cm (2ft x 18in)

Form

Semi-evergreen perennial

Soil

Poor to moderately fertile, well-drained

Aspect

Full sun or partial shade

Hardiness

Frost hardy (will need winter protection in cold areas)

Penstemon

Penstemon is a genus of approximately 250 species of deciduous, semi-evergreen or evergreen perennials and subshrubs growing in a variety of habitats from open plains to sub-alpine and alpine areas, mostly originating from Northern and Central America.

Native Americans used all parts of the plant in various medicinal preparations, including poultices and teas, both externally and internally. They were particularly important in the treatment of sexually transmitted diseases.

The name comes from the Greek words, pente, meaning five, and stemon meaning a stamen, alluding to the five stamens, one of which is sterile. 

Penstemon 'Sour Grapes'

This is a large-leaved penstemon with large, tubular-bell-shaped purple/blue flowers, which are produced from mid-summer to early or mid autumn. It is easy to grow and will form large clumps every year, adding a glorious splash of colour in a sunny, well-drained border.

Cultivation

• Grow penstemons in poor to moderately fertile, very gritty, sharply drained soil in full sun.
• Remove the faded blooms regularly to prolong flowering.
• Apply a dry mulch around the base of the plant to protect the roots from frost damage and cut back in spring when new shoots appear low down on the stem.
• Lift and divide congested clumps in spring.

Propagation

• Sow seed in late winter or spring, in containers in a cold frame (cultivars won’t come true from seed).
• Take softwood cuttings in early summer or semi-ripe cuttings in midsummer.
• Divide in spring. 

AGM

The RHS Herbaceous Plant Committee awarded Penstemon 'Sour Grapes' an Award of Garden Merit (AGM) with the description:
'a distinct colour; a good doer; not too tall.'