Growing Tips: Delphinium

Quick Reference:

Perennial, a plant that usually does not flower until the second season and lives and flowers for multiple seasons thereafter. Cover seed with 1/16 to 1/8 inch fine soil. Seed requires darkness to germinate. Germination occurs in 18 to 20 days and is best when the soil temperature is a constant 70 degrees F. Seed spacing 1/2 to 3/4 inches. Space between plants in the garden, 20 to 30 inches. Plant height: 4 1/2 to 5 1/2 feet.

Where to plant:

Delphiniums like a sunny, wind-protected location with rich, well drained soil, delphiniums do not like acid soils, grow best in cool weather and prefer to be planted where they will grow permanently, they must be transplanted with care.

Planting Instructions:

In Alaska it is recommended that when perennial seed is planted directly in the garden, it not be planted until mid June to allow the soil to warm. It is preferred that the seed be started indoors in containers because the environment is easier to control. Start seed in individual plastic pots with drainage holes that have been filled with sterilized potting soil, sprinkle a few seed on the soil surface, cover tiny seed totally as they require darkness to germinate and water well for good seed-soil contact, the seed is sensitive to drying out. Cover the pots with black plastic to provide darkness and reduce evaporation and keep soil moist until seedlings emerge. Remove the plastic as soon as the seedlings start to sprout. When seedlings show their first green leaves water with a liquid solution of plant food, repeat every two weeks and place pots in full sun. When the seedlings are 1 to 1 ½ inches tall thin by clipping off all but the two biggest plants and after the last frost move pots outdoors until the plants become well established, 2 to 3 inches tall. When planting to their permanent location, clip off the weakest seedling leaving only one plant, make a hole in the garden for the young plant, fill it with water, carefully slide the moist root ball out of the plastic pot, transplant it in the hole making sure the roots are not injured and carefully press the soil around the root ball. Immediately water well to help reduce transplant shock.


Stake or cage plants to protect from wind. Water regularly by letting hose run at base of plant. Apply a complete plant food in spring before the plants have started to grow and again in mid-summer.