Set plants 18 to 24 inches apart. Cool conditions will encourage spikes to attain their maximum size; and choose a location in full sun, with a humus-rich, well-drained but moistureretentive soil (ideally of neutral to slight alkaline reaction).
Good drainage is essential; lighten soil with sand and compost, if necessary. Crowns should be placed 1 to 2 inches below the surface of the soil; deeper planting might lead to crown rot.
Delphiniums should be fed liberally with manure or a recommended fertilizer. After initial blooming, cut back blooming stalks to 6 inches above ground to promote a second bloom. Leaves must not be removed. Taller varieties, especially if exposed to wind, may require staking.
We recommend a winter mulch. To promote larger flowers and greater numbers, remove all but 5 young shoots, early in the season when they are 4 to 6 inches high. It is important to stake tall growing varieties and this is best done early in the season.
Zones 3-7 (but can be treated as a hardy spring annual in Zones 8-10)