Delphinium: complete guide

Overview

The Delphinium (Delphinium grandiflorum), also called Siberian Larkspur, is a magnificent perennial renowned for its deep blue flowers. This plant, native to Siberia and northern China, adds refined elegance to any garden border or cut-flower arrangement.

Under the right conditions, the plant reaches heights of 50 to 100 centimeters with densely packed flowers along tall stems. The blooming period extends from June to August, providing prolonged color display.

Appearance & Bloom

The Delphinium distinguishes itself through characteristic, elegantly lobed foliage and impressive flower spikes. The plant grows upright with thin, sturdy stems.

The flowers are the star of the show. They feature a deep blue color, sometimes with white or pink varieties. Each flower is approximately 3 to 4 centimeters large and features a distinctive spur. Flowers are arranged in dense, conical spikes.

After blooming, seed capsules form that can remain decorative until season's end. Foliage stays attractively green throughout the growing season.

Ideal Location

The Delphinium thrives best in warm, sunny locations with at least 6 hours of direct sunlight daily. Afternoon shade can prevent flowers from opening too quickly.

The plant tolerates wind poorly due to its slender stems. Place it in a sheltered spot, possibly behind lower-growing plants that provide support.

A cool, moist summer is ideal. In hot, dry regions, the plant may wilt prematurely.

Soil

The Delphinium thrives best in well-draining, nutrient-rich soil with a pH of 6.0 to 7.5. It prefers neutral to slightly alkaline soil.

Heavy clay soils should be amended with sand and organic material. Ensure the soil does not become waterlogged.

A top dressing of compost in spring provides extra nutrition and improves soil structure.

Watering

The Delphinium needs regular moisture, especially during dry periods. Keep the soil consistently moist but not waterlogged.

Water at the base of the plant, not on the leaves, to prevent fungal diseases. In hot periods, daily watering may be necessary.

During the blooming period, consistent moisture is essential for prolonged flowers.

Pruning

The Delphinium benefits from regular maintenance to improve appearance. Remove wilted flowers regularly to encourage continued blooming.

When the plant dries out at season's end, cut it back to 10 centimeters above ground. This helps prepare the plant for next season.

Young plants can be pinched when about 15 centimeters tall, encouraging branching and fuller growth.

Maintenance Calendar

Spring (March-May): Clean up the plant by removing old, dead stems. Water regularly as growth begins. Support tall varieties with stakes.

Summer (June-August): This is the blooming period. Ensure consistent moisture. Remove wilted flowers regularly. Feed to support blooming.

Autumn (September-October): Leave seedheads for decoration until they turn brown. In early October, cut the plant back.

Winter (November-February): The plant rests. No special maintenance needed. Limited feeding if desired.

Winter Hardiness

The Delphinium is fully winter-hardy in temperate climates. The plant tolerates frost of -15 to -20 degrees Celsius without problems.

In very wet winters, crown rot can occur. Well-draining soil is therefore essential. In heavy clay areas, raising the planting location is advisable.

Dieoff after frost is normal and not a problem, as the plant regrows from the roots.

Companion Plants

The Delphinium works beautifully with other perennials in borders. Good combinations include:

Low-growing plants like fairy wand, coneflower, and pink flamingo accent the blue color.

White flowers like bugbane or yarrow create attractive contrast.

Cut flowers like roses, lilies, and baby's breath pair well with Delphinium in bouquets.

Closing Thoughts

The Delphinium is an essential plant for those wanting elegance and color in their border. With attention to drainage, moisture, and regular maintenance, this plant delivers beautiful blue flowers for years. A classic that never goes out of style.

Looking for plant material? Visit gardenworld.app/en or gardenworld.app/nl for more information and resources.