How to Grow Delphiniums: Complete UK Care Guide

Delphiniums produce some of the tallest, most dramatic flower spires in the UK border, in shades of blue, purple, pink and white through early summer. They need a sunny, sheltered spot, rich soil, sturdy staking and vigilant slug control, but the reward is a spectacular display that can be extended with the Chelsea chop technique.

Attribute	Detail
Botanical name	Delphinium elatum hybrids
Plant type	Herbaceous perennial
Height & spread	1–2m x 0.6–1m
Hardiness	RHS H6 (fully hardy)
Position	Full sun, sheltered from wind
Soil	Fertile, moist but well-drained
Flowering period	June to July, with a possible second flush
Difficulty	Moderate; needs staking and slug protection

Choosing varieties

The Elatum Group produces the classic tall spires, while Belladonna types are shorter and more branching, useful where staking space is limited.

Variety	Colour	Height	Notes
'Blue Nile'	Rich blue with white eye	Tall	Classic Elatum type, needs staking
'Faust'	Deep violet-blue	Tall	Strong, sturdy stems
Pacific Giant Series	Mixed blues, pinks, whites	Very tall	Popular, often grown from seed
'Sungleam'	Cream-white	Tall	Elegant, good for cutting
Belladonna Group 'Volkerfrieden'	Deep blue	Medium	Branching habit, less staking needed

Where and when to plant

Plant delphiniums in spring or early autumn in a sunny position sheltered from strong winds, as exposed sites cause stems to snap. Choose fertile, well-drained soil enriched with organic matter, avoiding sites prone to waterlogging in winter. Pair them with other cottage-garden classics; see our flowers and how-to guides for border planning ideas.

How to plant

1. Dig a hole and enrich the soil with well-rotted manure or compost.
2. Set the plant at the same depth it was growing in its pot.
3. Space plants at least 60–90cm apart to allow airflow.
4. Water in thoroughly.
5. Apply slug protection immediately around the crown.
6. Insert stakes or a support ring while plants are still small.

Watering and feeding

Water regularly during dry spells, especially while plants are establishing and as flower spikes develop. Feed in spring with a balanced fertiliser, and apply a potash-rich feed such as tomato feed as flower buds form to encourage strong blooms. Mulch annually with well-rotted organic matter to retain moisture and boost fertility.

Pruning, cutting back, deadheading and the Chelsea chop

Deadhead the main flower spike once blooms fade by cutting back to a strong side shoot, which encourages secondary flowering later in summer. The Chelsea chop, carried out in late May, involves cutting some stems back by about a third; this delays flowering on those stems, staggering the display and extending the overall flowering season. Cut all growth down to ground level in autumn once foliage has died back.

Dividing and propagation

Delphiniums are relatively short-lived and benefit from being divided every three to four years in spring, lifting the clump and splitting the crown with a spade, ensuring each division has roots and shoots. Basal cuttings taken in spring, when new shoots are around 7–10cm, root readily in a free-draining compost and are the best way to propagate named cultivars true to type.

Growing in pots

Shorter varieties or Belladonna types can be grown in large, deep pots using a loam-based compost such as John Innes No. 3 for stability. Stake plants securely as pots can be top-heavy, water more frequently than border plants, and feed regularly through the growing season.

Common problems

Problem	Symptom	Fix
Slugs and snails	Shredded young shoots in spring	Use nematodes, copper barriers and torchlight checks
Powdery mildew	White powdery coating on leaves	Improve air circulation, water at the base, remove affected leaves
Wind damage	Snapped or leaning stems	Stake early and choose a sheltered site
Crown rot	Blackened, collapsing base	Improve drainage, avoid waterlogged soil

Month-by-month care calendar

Month	Task
March	Protect emerging shoots from slugs; feed with balanced fertiliser
April	Install stakes or support rings; divide if needed
Late May	Perform Chelsea chop on selected stems
June–July	Main flowering period; deadhead spent spikes
August	Enjoy secondary flowering; keep watering in dry spells
September	Take basal cuttings if desired
Autumn–Winter	Cut back foliage after die-back; mulch the crown