Buddleja davidii 'Castle Blue'

RHS Plant Profile
butterfly bush 'Castle Blue'

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A shrub up to 2m high, with deciduous, narrow, lance-shaped, light green leaves up to 18cm long, and early-flowering panicles up to 25cm long and up to 10cm across of very fragrant, pinkish lilac flowers in summer

Position

Full sun

Soil Types

Sand, Chalk, Loam, Clay

Max Height

1.5-2.5 metres

Max Spread

1.5-2.5 metres

Size

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

Growing Conditions

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

Position

Full sun
Aspect
South–facing or West–facing or East–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

Fragrance Flower
Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Scrophulariaceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Bushy
Genus
Buddleja can be evergreen or deciduous shrubs, occasionally trees or scrambling climbers with simple leaves and panicles of small, tubular fragrant flowers
Name Status
Unresolved

How to Grow

Cultivation

Grow in well-drained soil in full sun. See buddleja cultivation for more detailed advice

Propagation

Propagate by hardwood cuttings in autumn, or by heeled semi-hardwood cuttings in summer

Suggested planting locations and garden types

  • Wildlife gardens
  • Cottage and informal garden
  • City and courtyard gardens
  • Coastal
  • Flower borders and beds

Pruning

Pruning group 6

Pests

May be susceptible to aphids, capsid bugs, caterpillars, earwigs, figwort weevils, glasshouse red spider mite, leaf and bud eelworm, and mullein moth

Diseases

May be susceptible to honey fungus, fungal leaf spot, and virus diseases