Penstemon cobaea

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prairie beard-tongue

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Other common names

cobaea-flowered penstemon, dew flower

Plants for pollinators
Herbaceous Perennial
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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

Position

Full sun

Soil Types

Loam, Sand

Max Height

0.5-1 metres

Max Spread

0.5-1 metres

Size

Time to Maturity
2–5 years
Max Spread
0.5-1 metres
Max Height
0.5-1 metres

Growing Conditions

Loam Sand
Moisture
Well–drained or Moist but well–drained
pH
Alkaline or Neutral

Position

Full sun
Aspect
West–facing or South–facing
Exposure
Exposed or Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

  • H1A: under glass all year (>15C)
  • H1B: can be grown outside in the summer (10 - 15)
  • H1C: can be grown outside in the summer (5 - 10)
  • H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
  • H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
  • H4: hardy through most of the UK (-10 to -5)
  • H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
  • H6: hardy in all of UK and northern Europe (-20 to -15)
  • H7: hardy in the severest European continental climates (< -20)
H6

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

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