Buddleja 'Blue Knight' (Monarch Series)

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A bushy, deciduous shrub to around 180cm in height, with narrow, lance-shaped grey-green leaves. Clusters of very long flowers on arching spikes open pale lavender-blue from July to September, turning to a vibrant purple-blue as they mature

Position

Full sun, Partial shade

Soil Types

Chalk, Loam, Sand

Max Height

1.5-2.5 metres

Max Spread

1-1.5 metres

Size

Time to Maturity
2–5 years
Max Spread
1-1.5 metres
Max Height
1.5-2.5 metres

Growing Conditions

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

Position

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

How to Grow

Cultivation

Grow in fertile well-drained soil in full sun. deadhead spent flowers to prolong the season. See buddleja cultivation for more detailed advice

Propagation

Propagate by stem cuttings in summer

Pruning

pruning group 6; Prune in early spring when the risk of frost has passed and new growth is appearing

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