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Herbaceous Perennial

Delphinium 'Guardian Blue' (Guardian Series)

delphinium 'Guardian Blue'

An upright herbaceous perennial 1.2m high with divided green leaves and strong stems, especially suitable for cutting, of deep blue flowers with white centres in early summer; delphiniums may be visited by bumblebees, especially long-tongued bumblebees

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Ultimate height

1–1.5 metres

Time to ultimate height

2–5 years

Ultimate spread

0.5–1 metres

Chalk

Loam

Sand

Moisture

Moist but well–drained

pH

Acid, Alkaline, Neutral

	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Full sun

Aspect

South–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)

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 but moisture-retentive soil in full sun, in a position sheltered from strong winds, and provide stakes or other supports. See staking: perennials and delphinium cultivation for further advice

Propagation

Propagate by basal softwood cuttings in spring, or by division in early spring or early autumn

Suggested planting locations and garden types

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

Pruning

No pruning required except deadheading, cutting spent flower spikes back to flowering sideshoots, and cutting all growth stems down to ground level at the end of the growing season

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

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