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Herbaceous Perennial

Penstemon cobaea
  • RHS Plants for pollinators

prairie beard-tongue

A clump-forming perennial to 60cm in height, with large green oval leaves and erect spires of large, impressive, pale to deep purple, bell-shaped flowers; blooms from spring into early summer

Other common names
dew flower
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Size
Ultimate height
0.5–1 metres
Time to ultimate height
2–5 years
Ultimate spread
0.5–1 metres
Growing conditions
Loam
Sand
Moisture
Well–drained, Moist but well–drained
pH
Alkaline, Neutral
Colour & scent
StemFlowerFoliageFruit
Spring Purple Green
Summer Purple Green
Autumn Green
Winter
Position
  • Full sun
Aspect

West–facing or South–facing

Exposure
Exposed or Sheltered
Hardiness
H6
Botanical details
Family
Plantaginaceae
Native to GB / Ireland
No
Foliage
Deciduous
Habit
Clump forming
Genus

Penstemon may be deciduous or evergreen perennials or subshrubs, with simple, narrow leaves and racemes or panicles of bell-shaped or funnel-shaped flowers in summer and early autumn

Name status

Correct

How to grow

Cultivation

Grow in fertile, moist but well-drained soil in full sun or partial shade. In cold areas, protect plant overwinter with a dry winter mulch. See penstemon cultivation for further advice

Propagation

Propagate by softwood cuttings in early summer or semi-ripe cuttings in midsummer

Suggested planting locations and garden types
  • City and courtyard gardens
  • Cottage and informal garden
  • Gravel garden
  • Patio and container plants
  • Rock garden
  • Prairie planting
  • Wildflower meadow
  • Wildlife gardens
  • Flower borders and beds
Pruning

Remove spent flower spikes to help encourage a long season; cut all stems down to low-growing shoots in mid- to late March

Pests

May be susceptible to aphids, slugs, snails and chrysanthemum eelworm

Diseases

May be susceptible to Powdery mildews

Get involved

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