Delphinium 'Blue Lace'

RHS Plant Profile
delphinium 'Blue Lace'

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delphinium 'Blue Lace' RHS
Herbaceous Perennial
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A tall herbaceous perennial with flower spikes reaching up to 1.8m. In summer, densely-packed spires of semi-double sky-blue flowers, some with a lavender pink flush, are held above the deeply-cut, mounded foliage

Position

Full sun

Soil Types

Chalk, Clay, Loam, Sand

Max Height

1.5-2.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
2–5 years
Max Spread
0.1-0.5 metres
Max Height
1.5-2.5 metres

Growing Conditions

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

Position

Full sun
Aspect
West–facing or East–facing or South–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)
H5

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Ranunculaceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Columnar upright
Potentially harmful
Humans/Pets: Harmful if eaten. Wear gloves and other protective equipment when handling. For further information and contact numbers regarding pets, see the HTA guide to potentially harmful plants
Genus
Delphinium can be annuals, biennials or perennials, with palmately lobed basal leaves and showy bowl-shaped flowers in spikes, racemes or panicles
Name Status
Accepted

How to Grow

Cultivation

Grow in a fertile, well-drained soil in full sun; shelter from strong winds and stake well (see staking perennials). Apply a balanced liquid every couple of weeks in the growing season. For the best flower spikes thin shoots when 7cm high to leave a minimum of 2-3 shoots on young plants and 5-7 shoots on established plants. See staking perennials and delphinium cultivation for further advice

Propagation

Propagate by taking pencil thick basal cuttings in early spring

Suggested planting locations and garden types

  • Cottage and informal garden
  • Cut flowers
  • Flower borders and beds
  • Wall side borders

Pruning

Deadhead spent flower spikes. After flowering, cut down all growth to ground level. If fed and watered well, a second flush of flowers may be produced in autumn

Pests

May be susceptible to aphids, earwigs, delphinium leaf miner, delphinium moth caterpillars, slugs, snails and caterpillars

Diseases

May be susceptible to powdery mildews, delphinium black blotch, crown rot and viruses