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Delphinium 'Blue Nile' AGM

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© RHS

Characteristics

Plant type

Herbaceous Perennial

Habit

Columnar/Upright

Toxicity

All parts may cause severe discomfort if ingested

Resilience

Hardiness

H5 (hardy - cold winter)

Colour

Flower

Blue and White in Summer

Foliage

Dark Green in Autumn, Spring and Summer

Size

Ultimate height

1-1.5 metres

Ultimate spread

0.5-1 metres

Time to ultimate height

2-5 years


Preferred common name

delphinium 'Blue Nile'

Family

Ranunculaceae


Delphinium can be annuals, biennials or perennials, with palmately lobed basal leaves and showy bowl-shaped flowers in spikes, racemes or panicles

'Blue Nile' is an herbaceous perennial to 1.5m in height, with divided, dark, glossy green leaves and erect racemes of white-eyed, mid-blue, semi-double flowers

How to grow

Sunlight

  • Full sun

Aspect

  • South-facing, East-facing or West-facing
  • Sheltered

Cultivation

Grow in a fertile, well-drained soil in full sun; shelter from strong winds and stake well. Apply a balanced liquid every couple of weeks in the growing season. For 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

Soil

  • Moist but well-drained or Well-drained
  • Acid, Alkaline or Neutral
  • Loam, Chalk or Sand

Propagation

Propagate by taking pencil thick basal cuttings in early spring

Suggested planting locations and garden types

Cottage/Informal Garden, Flower borders and beds or Cut Flowers


How to care

Pruning

Deadhead by cutting spent flower spikes back to small flowering side shoots. Cut down all growth to ground level after it has withered in autumn.

Pests

Prone to slugs, snails, leaf miners and caterpillars

Diseases

May be subject to powdery mildews, delphinium black blotch, crown rot and a virus