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Herbaceous Perennial

Delphinium 'Finsteraarhorn'

delphinium 'Finsteraarhorn'

A deciduous, herbaceous perennial that reaches approximately 1.7m in height when in flower. It forms a mound of green, palmately lobed leaves and dense spikes of gentian blue, single flowers flushed with pinkish purple, with black centres, in summer

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Ultimate height

1.5–2.5 metres

Time to ultimate height

1–2 years

Ultimate spread

0.5–1 metres

Chalk

Loam

Sand

Moisture

Moist but well–drained, Well–drained

pH

Acid, Alkaline, Neutral

	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Full sun

Aspect

South–facing or West–facing or East–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)

Botanical details

Family: Ranunculaceae
Native to the UK: No
Foliage: Deciduous
Habit: Columnar upright, Clump forming
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 fertile, well-drained soil in full sun. Shelter from strong winds and provide support (see staking: perennials). Divide every 2-5 years to maintain vigour. See staking: perennials and delphinium cultivation for further advice

Propagation

Propagate by division or by basal softwood cuttings in spring.

Suggested planting locations and garden types

City and courtyard gardens
Cottage and informal garden
Cut flowers
Flower borders and beds
Wall side borders

Pruning

Deadhead main stem after flowering to encourage side shoots to flower. Cut back to ground level in autumn

Pests

May be susceptible to aphids, slugs, snails, leaf miners and caterpillars, including swift moth caterpillar

Diseases

May be susceptible to delphinium black blotch, Powdery mildews, grey moulds, crown rot (on mature plants) and occasionally cucumber mosaic virus

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