Delphiniums: Planting, Growing, and Care for Majestic Spikes

Delphiniums are perennials prized for their showy spikes of colorful summer flowers in gorgeous shades of blue, pink, white, and purple. They shine in cottage gardens and cutting gardens alike.

Delphiniums are a gardener's favorite—and sometimes a challenge. They prefer moist, cool summers and falter in hot, dry conditions. They also dislike sudden wind or rain.

Except for dwarf perennials, most delphiniums require staking.

Planting Delphiniums

• Grow in fertile, well-drained soil in full sun to light shade, sheltered from strong winds.
• Plant in spring. Prepare soil by mixing in 2–4 inches of compost.
• Delphiniums are very difficult from seed. Buy potted plants from a nursery.
• Dig a hole twice the container's diameter. Ensure the root ball's top sits level with the soil.
• In spring, broadcast lime, wood ashes, or a mix over this alkaline-loving perennial.

Care and Maintenance

• Install supports by mid-spring or when plants reach 12 inches. Low-growing types need twiggy brushwood; tall, large-flowered types need sturdy stakes.
• Keep soil consistently moist. Water if rainfall is under 1 inch per week.
• For quality flower spikes, thin shoots at 3 inches high: leave 2–3 shoots on young plants, 5–7 on established ones.
• During growth, water freely and apply balanced liquid fertilizer every 2–3 weeks.
• Deadhead by cutting spent spikes back to small flowering side shoots.
• After blooming, cut flower stalks to the ground—new, smaller stalks will develop and withstand cold and light frosts.
• If dividing in spring, remove and replant new plants from the clump's outer edges. Discard the woody old center.

Pests and Diseases

• Slugs, snails, and cyclamen mites.
• Powdery mildew, Southern blight, bacterial and fungal spots, gray mold, crown and root rot, white rot, rust, white smut, leaf smut, damping off.

Harvest and Storage

• Excellent for cutting gardens. Bring blooms indoors as they open for rebloom.
• Add sugar, lemon juice, and bleach to arrangements, or use commercial flower preservative.

Recommended Varieties

Delphiniums range from dwarf to tall (6+ feet).

• Belladonna Group: Upright, loose, branching perennials with single flowers, 3–4 feet tall. 'Blue Bees' — clear blue with white centers.
• Elatum Group: Tallest spiked hybrids, 6+ feet. 'Blue Nile' — medium, semi-double bright mid-blue with white centers. 'Bruce' — tall, semi-double violet-purple, paler toward center with brown centers.
• Pacific Hybrids: Similar to Elatum but shorter, short-lived, often grown as annuals/biennials. 'King Arthur' — plum flowers with white centers, 5–6 foot spikes.

Wit & Wisdom

• Caution: Very young delphinium plants and seeds are poisonous. Ingestion can cause nausea, muscle twitching, paralysis, and even death.