Delphinium Black Knight

• Variety: Black Knight
• Latin name: Delphinium elatum 'Black Knight' (Pacific Giant Series)
• Type: Herbaceous perennial
• Flower: Deep violet-purple with dark eye
• Height: 150cm (5ft)
• Spread: 60cm (2ft)
• Flowering: June–July
• Hardiness: Fully Hardy (H7)
• Pruning: Cut back after flowering; cut to ground in autumn
• RHS AGM: No
• Sold as: Pot-grown plants
• Plant outdoors: Spring, in rich moist soil in a sheltered position
• Delivered: Spring and summer. Collection from Castle Cary also available.

Delphinium 'Black Knight' is a Pacific Giant hybrid with deep violet-purple spires and dark eyes, reaching 150cm in June and July. The deepest-coloured of the three Pacific Giants we stock — a saturated, almost inky purple that is the strongest statement any border delphinium makes.

Black Knight – The Darkest of the Three

In the Arthurian naming scheme of the Pacific Giants, Black Knight has the most dramatic identity to live up to — and the colour matches it. The violet-purple of Black Knight is noticeably deeper than standard blue delphiniums, with a dark, near-black eye at the centre of each individual floret that intensifies the effect at close range. At 150cm the spires cast weight as well as colour down the border. Placed against a light wall or a pale companion planting — white agapanthus, the silver foliage of a large artemisia — the dark purple reads with unusual force.

Like all Pacific Giants, Black Knight is seed-raised, which means the shade of purple will vary slightly from plant to plant. The colour range is tight — deep violet through rich purple — and the variation is part of what makes a group planting of Black Knight look natural rather than uniform. The same cultural requirements apply as to all show delphiniums: stake early, protect emerging shoots from slugs in March and April, plant in rich moist soil with good drainage, and give it full sun. Cut the main spike back to side shoots after the primary flowers are over and feed generously — in a good year you get a secondary flush in August.

Companions for Black Knight

The dark violet of Black Knight works best against light or contrasting colours. Delphinium Galahad in pure white alongside is the most direct contrast — the Victorian-era tradition of alternating dark and white delphiniums in the back border still produces one of the finest June effects in a garden. Campanula latifolia Alba at 120cm provides white bells at a complementary height through the same period. At mid-border level, Delphinium Astolat in pink-lilac introduces warm tone against the cool purple. Lupin Gallery White in front adds a further vertical white element in late May and June before the delphiniums come into their own.

Why Ashridge?

We use peat-free compost and biological pest controls. Delphiniums reward proper attention — stake early, protect from slugs, feed well — and Black Knight, at its best, justifies every bit of effort. Every plant is guaranteed. See the full perennial collection.

Frequently Asked Questions

What is the difference between Delphinium Black Knight and Delphinium Galahad?

Colour, entirely. Black Knight is deep violet-purple with a dark eye — one of the richest purples available in a perennial. Galahad is pure white with a white eye. Both are Pacific Giant series at the same height and with identical growing requirements. Plant them together for the classic light-and-dark delphinium contrast.

How do I get the deepest colour from Black Knight?

Full sun and generous feeding. Delphiniums grown in rich, moist soil and fed with a balanced fertiliser from March onwards develop the strongest pigmentation. Dry or impoverished soil produces smaller spires and often paler colouring. The dark eye of Black Knight is most pronounced in fresh-opened flowers; it softens slightly as the florets age.

Can I grow Delphinium Black Knight in a pot?

Not really — the root system, height, and staking requirements make it impractical for all but very large containers. It needs room to develop and a stable anchor point for the stakes. A generous border with good soil is the right home for it.

Do delphiniums attract bees?

Yes, particularly bumblebees. The florets produce nectar accessible to long-tongued bees, and Black Knight in full flower on a warm June morning is reliably busy with them. The plant is also a significant attraction for certain hawkmoth species in some areas.

When is the best time to plant delphiniums?

Spring is ideal — established plants cope better with the following winter than those planted in autumn. Choose a sheltered spot with rich moist soil and get the stakes in early. Once planted, water well until established and do not let the soil dry out during the growing season.