Sour Grapes penstemon

Sun

Full sun; light afternoon shade is helpful in hot inland gardens.

Water

Water regularly during establishment, then during prolonged dry spells. Let the soil surface dry between waterings; avoid persistently wet roots.

Soil

Well-drained loam, sandy soil or improved gravelly soil. Avoid waterlogged ground and heavy clay that stays wet through winter.

Height

2-3 ft (0.6-0.9 m)

Spread

1.5-2 ft (0.45-0.6 m)

Flowers

Summer into autumn; tubular pinkish-purple flowers develop muted lavender-blue tones as they age.

Foliage

Narrow, lance-shaped green leaves on upright, branching stems; evergreen in mild winters, partly or fully deciduous in colder conditions.

Growth

Moderate

Care needed

Medium

• Pollinators
• Deer resistant
• Drought tolerant
• Heat tolerant
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Moderate

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

2. After 1 year

   1.5 ft (0.45 m)

3. After 2 years

   2 ft (0.6 m)

4. After 3 years

   2.5 ft (0.75 m)

   full size

About 3 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Growth rate

Moderate

• Plant in spring in colder regions so roots establish before winter.
• Water at soil level during extended dry weather, without keeping the root zone constantly damp.
• Apply a light dressing of compost in spring; avoid heavy nitrogen feeding, which encourages floppy growth.
• Keep mulch away from the crown and improve drainage where winter rainfall is heavy.
• Take cuttings regularly to replace plants that become woody or fail after a hard winter.

Pruning. Remove faded flower stems just above a healthy leafy shoot to encourage further bloom. Leave the main stems standing over winter, then shorten them to strong new growth in spring after the risk of hard frost has passed.

Spring

Check for new growth before cutting back winter-damaged stems; remove dead material.

Late spring

Plant out after hard frosts, water thoroughly and apply a light compost dressing.

Summer

Deadhead spent flower stems and water during prolonged dry spells.

Late summer

Take non-flowering cuttings as insurance against winter losses.

Autumn

Leave the main stems intact and clear fallen leaves from around the crown.

Winter

Keep container plants sheltered from prolonged rain and hard frost; water sparingly without letting the root ball dry completely.

• Plant in small groups through the middle of a sunny border for a long season of soft purple-blue flowers.
• Combine with silver-leaved plants and ornamental grasses in a well-drained gravel garden.
• Weave among roses and hardy geraniums in cottage-style planting.
• Grow in a large, freely draining container near a terrace where the flower markings can be seen closely.

Garden styles it suits: Cottage garden, English country, Dry gravel garden, Pollinator garden, Blues and silvers and Pastel border.

Plant it with: Lavender, Catmint, Hardy geranium, Yarrow, Lamb's ears and Feather reed grass.

Wildlife: Tubular flowers attract bees and, in North America, hummingbirds. This garden hybrid is not a substitute for locally native penstemons where native habitat planting is the priority.

• Winter root or crown rot: improve drainage, keep mulch off the crown and avoid planting in winter-wet hollows.
• Frost damage: leave stems standing until spring and keep backup cuttings under frost-free cover in colder gardens.
• Slugs and snails on young shoots: inspect new growth and use barriers or locally approved slug controls if needed.
• Aphids on tender shoots: dislodge with water or treat persistent colonies with insecticidal soap according to the label.

Not known to be toxic to people, cats, dogs or horses. No part is regarded as a common poisoning hazard, but it is an ornamental plant, not a food plant.

• Common foxglove (Digitalis purpurea)

  Foxgloves have broad, softly hairy leaves in a basal rosette and tall, usually one-sided flower spikes; 'Sour Grapes' has narrow leaves along branching stems.

• Husker Red beardtongue (Penstemon digitalis 'Husker Red')

  It has burgundy-tinted foliage and white to faintly pink flowers, rather than the green foliage and lavender-purple flowers of 'Sour Grapes'.

Penstemon refers to the flower's five stamens, including one sterile stamen whose hairs give rise to the common name beardtongue.

Propagation. Take softwood cuttings in late spring or semi-ripe, non-flowering shoot cuttings in late summer. Root in a free-draining medium and shelter young plants over winter; seed will not reliably reproduce the cultivar.

Accepted botanical name

Penstemon

Sources: GBIF (CC BY 4.0). The care and design notes are LandscapeGPT's own.