annual (warmer zones
) hardy perennial (zones
3 to 8)
3' to 5'
full sun to partial shade
rich, well-drained soil with a neutral to alkaline pH
early summer to fall
sky blue, dark blue, lavender, pink and white
green, maple-like leaves
tall back borders, cut flowers, and mass plantings
Delphiniums thrive in areas with cooler summers. Start with bedding plants or sow seeds indoors in late winter. Seeds should be cold treated for two weeks before being moved to a warmer temperature for germination. Mulch plants in spring to keep the soil moist and cool. Fertilize in spring with a 5-10-5 fertilizer and repeat during flowering. Stake in late spring when plants reach a height of 12 inches.
Delphiniums appreciate moist soil, but hate wet feet. To avoid crown rot, mound up soil around roots of each plant so soil slopes away from the stems, or plant in raised beds.