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Herbaceous Perennial

Delphinium 'Sweetheart'

delphinium 'Sweetheart'

A deciduous, herbaceous perennial that reaches approximately 1.8m in height when in flower. It forms a mound of green, deeply lobed leaves and stately flower stems of numerous rich rose to soft pink flowers with contrasting white centres, from summer to autumn

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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

Alkaline, Neutral, Acid

	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 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 fertile, well-drained soil in full sun. Shelter from strong winds and provide support. 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

Architectural
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

Diseases

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

Get involved

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