Delphiniums require soil that retains moisture but never becomes waterlogged (especially in winter). They are heavy feeders, succeeding best where the soil is deeply cultivated with lots of added organic matter. Apply a low-nitrogen fertilizer liberally in early spring. Staking is essential (see page 115.) Cut the spikes back to the top of the foliage after blossoming for repeat blooms in late summer and early fall.
Delphinium is one of the great plants of Europe. The belladonna types grow 4 to 5 feet tall and are the most durable varieties available (lasting 3 to 4 years) for American gardeners. They come in an assortment of blue, purple, and white shades but lack the grandeur of the more stately delphiniums of European gardens. The elatum hybrids, while long-lasting perennials in Europe, perform brilliantly in American gardens for just a year or two. This makes them magnificent, if somewhat expensive, annuals or biennials. They’re worth trying, though, especially in northern and coastal gardens. (‘Magic Fountains’ is shown here.)
ZONES: 3–8
BLOOM TIME: Summer
LIGHT: Full sun
HEIGHT: 48–60 inches
INTEREST: Light blue spikes on tall plants
Delphiniums must have full sun and should be planted at the back of the perennial border. They resent the heat and humidity of the Southeast, succeeding best where nights cool down. They are magnificent as cut flowers, providing height, color, and drama in mixed bouquets.