Gardening Articles: Flowers :: Perennials
Delightful Delphiniums (page 3 of 3)
by Charlie Nardozzi
Delphiniums look best in clumps of three to five plants planted in well-drained soil with a pH of 6.5 to 7. Sow new seed (delphinium seed loses viability quickly) indoors in January or February for spring planting, or in August or September for fall planting. If slugs and snails are problems in your area, it's better to plant in spring. Plants grown from spring-sown seed may flower the first year, but the flower spikes will be fewer and smaller, and come later in the season than normal.
In hot-summer areas of zones 7 and warmer, set out transplants in October or November in well-drained soil; they'll bloom the following March and April. Dwarf and heat-tolerant varieties produce the best flowers and are most likely to survive summer heat, especially if planted in part shade. Although plants struggle to survive the hot summers, they can take temperatures down into the teens in winter as long as the flower stems haven't formed.
Buying plants allows for better flower production the first year, but in either case, it won't be until the second year that the plants really start producing large flowers and multiple stems, especially for the tall hybrids.
The soil you plant your delphiniums in should be rich and porous, so proper soil preparation is critical. Plants grown in cool, moist soil often rot. If the soil is predominantly clay, it's best to use raised beds. Amend your soil with 3 to 4 inches of compost.
Plant seedlings 1 to 2 feet apart, being careful not to bury the root crown. Cover with a 4- to 6-inch layer of mulch to conserve moisture and keep the roots cool.
Regular fertilizing is important for good flower production. Side-dress the plants with compost or a balanced fertilizer such as 5-10-5 at planting time, when flower stems form, and again after flowering. When weeding, cultivate carefully around the crown, since it is at the surface.
As soon as flowering finishes in zones 3 through 6, cut off flower stems to prevent seed formation. This often stimulates a repeat flowering later in fall.
Staking: Support Groups
The flower stems of tall varieties, such as those of the Pacific Giants series, are amazingly pliable and will withstand light wind and rain, but they do need some support for more severe weather. Many methods and products help support plants and flowers, but here is one of the easiest and most effective.
When the plants are a foot tall, place three 4-foot-long bamboo or plastic-coated metal poles in a triangle around a plant or clump of plants. Encircle the poles with thick garden twine about 10 inches above the ground. Once the flower spikes form, make a second loop around the poles at a height just below the flower heads. Usually two loops are enough to support the flowers.
Instead of poles and twine, you can use tomato cages, linking stakes, or flower rings as long as the flower stems are supported just below their heads.
Charlie Nardozzi is the senior horticulturist at National Gardening Association.
Photography by Suzanne DeJohn/National Gardening Association