Strobilanthes pentastemonoides var. dalhousieana

RHS Plant Profile
smooth penstemon coneflower

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Herbaceous Perennial

An evergreen, bushy perennial to 1.2m tall and spreading via prostrate, rooting stems to 1.5m wide with ovate, dark green, serrated leaves to 13cm long . Tubular flowers borne in small clusters in summer are shades of blue, pale purple and pink

Position

Full sun, Partial shade

Soil Types

Loam, Sand

Max Height

1-1.5 metres

Max Spread

1.5-2.5 metres

Size

Time to Maturity
5–10 years
Max Spread
1.5-2.5 metres
Max Height
1-1.5 metres

Growing Conditions

Loam Sand
Moisture
Well–drained
pH
Acid or Alkaline or Neutral

Position

Full sun Partial shade
Aspect
South–facing or West–facing or East–facing
Exposure
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)
H2

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Acanthaceae
Native to GB/Ireland
No
Foliage
Evergreen
Habit
Bushy, Spreading branched
Genus
Strobilanthes can be evergreen or herbaceous perennials or subshrubs with simple, opposite leaves and spikes, cone-like clusters or loose panicles of tubular or funnel-shaped flowers
Name Status
Correct
Plant Range
W Himalaya, Bangladesh

How to Grow

Cultivation

Grow under glass in peat-free, loam-based compost in full light with shade from hot sun. Grow outdoors in light free draining soil in full sun to partial shade in a frost-free area

Propagation

Propagate by seed or softwood cuttings

Suggested planting locations and garden types

  • Cottage and informal garden
  • Low Maintenance
  • Flower borders and beds
  • Wall side borders

Pruning

If required can be cut back to limit height and spread

Pests

May be susceptible to glasshouse red spider mite

Diseases

Generally disease-free