Delphinium Galahad Group

RHS Plant Profile
delphinium Galahad Group

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Herbaceous Perennial
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A short-lived herbaceous perennial, often grown as an annual or biennial plant that produce spikes up to 1.8m tall densely-packed with large, semi-double white flowers throughout early and midsummer

Position

Full sun

Soil Types

Chalk, Sand, Loam

Max Height

1.5-2.5 metres

Max Spread

0.5-1 metres

Size

Time to Maturity
1 year
Max Spread
0.5-1 metres
Max Height
1.5-2.5 metres

Growing Conditions

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

Position

Full sun
Aspect
South–facing or East–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)
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
Unresolved

How to Grow

Cultivation

Grow in a fertile, well-drained but moisture-retentive soil in full sun; shelter from strong winds and provide stakes or other supports. See staking perennials and delphinium cultivation for further advice

Propagation

Propagate by seed, basal softwood cuttings or by division

Suggested planting locations and garden types

  • City and courtyard gardens
  • Cottage and informal garden
  • Wildlife gardens
  • 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, grey moulds, sclerotinia disease, crown rot and cucumber mosiac virus