Delphinium ~ Larkspur Plant Care Guide and Varieties
Delphinium is a stately, elegant perennial that is a standard in English cottage gardens. Mounds of dark green, glossy foliage are adorned with huge spikes of showy, spurred flowers in early summer. Another common name is larkspur, although this name usually refers to annual varieties.
About This Plant
Delphiniums thrive in regions with relatively cool and moist summers, and often struggle in hot, dry summer weather. However, some new varieties are more tolerant of heat.
Delphiniums are available in a range of sizes, from dwarf varieties less than 2 feet tall to those with towering, 6-foot blooms. Flower color includes blue, red, white, and yellow; however, the rich, clear blues are especially prized by many gardeners. The plants bloom in late spring to early summer, and the flowers are suitable for cutting.
Good for cut flowers
Select a site with full sun to light shade and well-drained soil. Choose an area protected from strong winds to keep tall, top-heavy varieties from blowing over.
Plant in spring, spacing plants 1 to 3 feet apart, depending on the variety. Prepare the garden bed by using a garden fork or tiller to loosen the soil to a depth of 12 to 15 inches, then mix in a 2- to 4-inch layer of compost. Dig a hole twice the diameter of the pot the plant is in. Carefully remove the plant from its container and place it in the hole so the top of the root ball is level with the soil surface. Carefully fill in around the root ball and firm the soil gently. Water thoroughly.
Apply a thin layer of compost each spring, followed by a 2-inch layer of mulch to retain moisture and control weeds. Water plants during the summer if rainfall is less than 1 inch per week. Soil should never dry out. Stake tall varieties to prevent hollow flower stalks from snapping in the wind, and deadhead after flowering to encourage rebloom. After the first killing frost, cut stems back to an inch or two above soil line. Divide plants every three to four years as new growth begins in the spring, lifting plants and dividing them into clumps.
Include larkspur in your flower garden and the tall, stately spikes will produce blooms in shades of purple, blue, rose, pink and white all summer long. Most strains are tall enough to be a backdrop for other flowers, and they’re especially beautiful planted along a wall or a garden fence. Small varieties are compact enough to make a colorful border plant. Clip a few for a fresh floral arrangement or dry them for a cheery winter bouquet.
Stake larkspur to prevent it from breaking in the event of a strong wind. Some larkspurs can grow to a height of 5 feet or more, and although the stalks are sturdy, the blooms are heavy and can cause the plant to lean and break. The easiest way to stake a tall plant like larkspur is to insert a wooden stake into the soil about 3 inches from the larkspur’s stem. Tie the stem to the stake loosely with soft twine or a strip of pantyhose.
Water larkspur twice a week, and more during dry periods, and give it an all purpose fertilizer every other week. Just before the larkspur begins to bloom, give it a high potassium fertilizer. Check the instructions on the package label for amounts.
Cut the blooms for cut flower arrangements just before they reach full bloom. Use garden shears or sturdy scissors to cut long stems to arrange in a vase. Don’t worry about removing too much stem from the plant, as pruning will encourage more blooms. Deadheading any spent blossoms will allow the plant’s energy to go into developing new larkspur flowers. To deadhead, just clip the stem below the spent blossom, or pinch it off with your fingers.
Watch the larkspur for signs of problems. Although larkspur isn’t prone to insect problems, it can develop mildew, which is a type of fungus that can be recognized by white or black spots on either side of the leaves, or by a powdery, stringy substance. If the problem persists, the leaves will become distorted, or will turn brown or yellow and will eventually fall off. Treat the infected plant immediately with a fungicide, following the directions on the label carefully.To avoid mildew, make sure the plant has good air circulation and adequate sunlight.
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