How to Grow Delphinium Plants in your Garden

Gardener's HQ Guide to Growing Larkspur

Delphinium plants can be either hardy or half hardy perennials.

Delphinium are very variable in height, depending on the variety. They can grow anything from 15 cm (6 inches) to over 2 metres (6 feet) in height.

They bloom with tall spires with flowers of blue, pink, purple, yellow, or white.

The timing of flowering is variable between species of Delphinium, and can be anything from the end of spring to autumn.

delphinium
Tall Delphiniums photograph by cacophonyx.

larkspurs
Larkspurs - Delphinium, Huntington Library Gardens by DominusVobiscum.

Delphinium Growing and Care Guide

Common Names: Larkspur, Delphinium, Forking Larkspur.
Life Cycle: Hardy perennial. Half hardy perennial
Height: 4 to 80 inches (10 to 200 cm).
Native: Northern Hemisphere.
Family: Ranunculaceae.

Growing Region: Zones 3 to 9.
Flowers: Species dependent: Late spring, and/or summer and/or early autumn.
Flower Details: White, blue, purple, yellow, pink. Spurs. Raceme. Sepals resemble petals.
Foliage: Maple-like. Palmate.

Sow Outside: Cover seed. Start of spring or the beginning of autumn. Spacing: Smaller species 8 to 18 inches (20 to 45 cm); Larger species 24 to 40 inches (60 to 100 cm).
Sow Inside: Germination time: two weeks to one month. Temperature 50 to 55°F (10 to 12°C) in the dark. First mix seeds in a moist growing medium, place in a freezer bag, then stratify by refrigeration for two to three weeks. Sow stratified seasons about two months in advance. Transplant outdoors early in spring or autumn.

Requirements and care: Full sunlight or light shade. Soil pH 5.5 to 7.0. Good drainage. Deep soil, rich soil. Regular watering when plant is growing. Provide an early spring feed. Following first bloom remove faded flowers. Supply a further feed. Provide support for taller varieties. Cut back old growth when new growth reaches about 9 inches (27 cm). Propagate: by dividing in the spring.
Miscellaneous: Attractive to Bumble bees and moths such as the Small angel shade.

How to Grow Delphinium

When growing Delphinium outdoors from seed, they should be sown either at the beginning of spring or the beginning of autumn. Once sown, simply cover the seeds with topsoil.

The spacing will depend upon the variety (small species about 40 cm (16 inches) apart; large ones about 80 cm (32 inches) apart).

They can grow in either a sunny or lightly shaded location of the garden. This area should have good drainage.

The soil should be rich, deep, and have a slightly acidic to neutral pH of 5.5 to 7.

Caring for Delphinium

Once growing, Delphinium plants should be fed with fertilizer at the beginning of spring.

Taller varieties of Delphinium should be staked.

As soon as the first bloom is over, the flowers should be cut off. This will result in further growth. Once the new growth has reached about 20 cm (8 inches) then the old growth should be pruned off.

If you require more Delphinium plants, then they can be propagated by division. This can be carried out in the spring.

Common Questions

How many members does the Delphinium genus have?

The Delphinium genus has around 300 species currently.

Do members of Delphinium make a good garden or landscaping plant?

Yes, Delphinium are popular in gardens for their tall spires of colorful flowers and are excellent for adding height to borders.

Which Delphinium species are most frequently grown by gardeners?

The Delphinium elatum (Larkspur) is a favorite species among gardeners for its vibrant blue flowers.

Are members of the Delphinium plant genus fragrant?

Most Delphinium species are not notably fragrant but are prized for their visual appeal.

What is the perfect location to grow Delphinium?

Delphinium plants thrive best in a location with full sun or partial shade and well-drained, fertile soil.

Is Delphinium invasive in the USA, if so in which states?

Currently, Delphinium is not considered invasive in the USA.

How do I remove Delphinium plants from my garden?

To remove Delphinium plants, dig them up, ensuring to get all the root system to prevent regrowth.

Summary

The Delphinium genus comprises around 300 species of perennial flowering plants, native to the Northern Hemisphere. Known for their tall, showy spikes of colorful flowers, delphiniums are a favorite in cottage gardens and formal flower beds.

Delphiniums prefer cool summers and moist, well-drained soil in a sunny location. They can be grown from seeds or young plants and should be planted in spring. As tall plants, they often require staking to support their flower-laden stalks. Regular fertilizing and deadheading spent flowers will encourage repeat blooming.

I hope that you found this guide on how to grow Delphinium plants in your garden. You may also enjoy my gardening guides on how to grow Hellebore, Consolida plant, and Pulsatilla plants.