Delphiniums are majestic flowering plants. Their long, colorful flower spikes are spectacular additions to the garden.
Delphiniums have been cultivated and hybridized for many years resulting in some name confusion. Delphiniums are often call larkspurs. While the larkspur and delphinium are similar, they are actually different plant species. Many of the delphiniums grown in gardens today are hybrids of Delphinium x elatum. The name delphinium is derived from the Greek word delphis, which refers to the dolphin-shaped flower buds before they open. Flowers are usually blue, but also come in white, pink, red, violet, and purple. The true larkspur is Consolida ambigua. The common name larkspur comes from the shape of the flower, which resembles a lark's spur or claw. Larkspurs have daintier flower spikes with fewer florets and fine, more deeply cut leaves.
Some delphiniums grow up to 6 feet tall, making them excellent background plants. Others are much shorter. The Chinese delphinium (Delphinium grandiflorum) grows 2 to 3 feet tall and is a good choice as an accent in the middle or front of the perennial border. The Belladonna delphinium (Delphinium x belladonna) is a cross between D. elatum and D. graniflorum. Plants produce multiple flower stems that grow to 3 to 4 feet. 'Dwarf Pacific' hybrids grow only 2 feet tall. 'Blue Butterfly' is one of the shortest delphiniums maturing at 15 inches.
Delphiniums perform best in well-drained soils in full sun. They are heavy feeders and should be fertilized in early spring and later in the season. Stunted growth and yellow foliage are signs the plants need additional fertilizer.
The flower spikes of delphinium are hollow and brittle. Tall growing hybrids should be staked as wind and rain on the heavy, flower-laden spikes will cause the stems to snap and break. Stakes should be installed early in the growing season to prevent damage to the plant's root system and provide early support.
Most delphinium hybrids bloom from early to mid-summer. They are good cut flowers and will last about 6 to 8 days in a vase. Immediately after flowering, cut off the old flower stalk to encourage additional flowering in late summer or early fall. The flower spikes produced during the second flower display won't be as large or as full as the first bloom. The Chinese delphinium is a summer-blooming species. It blooms throughout the summer if the plants are cut back regularly.
Larkspur spikes can easily be air-dried. Harvest spikes when about four-fifths of the florets on the spikes are open. Remove the foliage and hang small bunches of spikes upside down in a dark, well-ventilated area. When the flowers feel papery, they should be stood upright to finish drying.
While delphiniums are spectacular plants, many are short-lived perennials. Most last only 2 or 3 years in the garden.
A word of caution to gardeners with small children. All parts of the delphinium and larkspur are poisonous.
This article originally appeared in the June 13, 1997 issue, pp. 92-93.