How to Sow and Plant Delphiniums

Delphinium may be grown from seed sown early indoors and transplanted outside after frost, or sown directly in the garden in summer, or grown from potted plants.

Indoor Method: Sowing Delphinium Seed Indoors:

• Sow seeds indoors 8-10 weeks before last spring frost.
• Sow 1/8 inch deep in seed-starting formula.
• Keep the soil moist at 70-75 degrees F.
• Seedlings will emerge in 21-28 days.
• As soon as seedlings emerge place on a sunny windowsill until the seedlings are 3-4 inches tall
• Transplant after all danger of frost.
• Before planting in the garden, seedling plants need to be “hardened off”. Accustom young plants to outdoor conditions by moving them to a sheltered place outside for a week. Be sure to protect them from wind and hot sun at first. If frost threatens at night, cover or bring containers indoors, then take them out again in the morning. This hardening off process toughens the plant’s cell structure and reduces transplant shock and scalding.

Direct Sow Method:

• Sow in full sun or light shade with a cool, moist organic soil.
• In milder areas, sow directly in the garden in mid to late summer.
• Sow seeds evenly and cover with 1/8 inch of fine soil.
• Firm the soil lightly and keep evenly moist.
• Be sure to keep the soil moist but not wet until the plants are established.
• Seedlings will emerge in 21-28 days.
• Thin to at least 18″ apart
• Thin to at least 18 inches apart when seedlings have three sets of leaves

This plant grows larger every year so staking is required by year 2 or 3 onwards. Most first-year plants grow to 18″ with one to three blooms.