Delphinium

Delphinium is a genus of herbaceous, flowering plants containing more than 500 species from temperate and subtropical regions of North America, Europe, Africa and Asia. The species, commonly called larkspurs, include annuals, biennials, and perennials and can often be found growing wild in forests or natural areas in rich woods and in mountains. Delphinium is a member of the buttercup family (Ranunculaceae). Its native range is eastern and northern Asia. The genus name comes from the Greek word "delphis" meaning "dolphin," in reference to the flower bud shape of some species resembling a dolphin.  

Delphiniums do best in fertile, medium moisture, well-drained soils in full sun and tolerate alkaline soils. The plant prefers cool summers but will do well if protected with afternoon shade in hot summer climates. Bloom time is May through mid-summer. It can be a challenge to grow them in humid summer climates south of USDA Zone 7. Delphiniums require considerable maintenance (staking, pruning, deadheading, disease control) in order to perform well in the garden. Plants, especially taller varieties, require protection from strong winds and rainstorms by means of shelter and staking. As a short-lived perennial, spent flowers should be promptly cut back to the basal foliage to encourage additional late summer and fall blooms. Some delphiniums spread in disturbed areas in woods and fields and can become weedy in gardens. Most of the plants sold commercially are complex hybrids. 

These incredibly showy flowers have their own category for Award as Garden of Merit in the Royal Horticultural Society. Delphinium-specific trials of merit have been in progress since 1916, transitioning in 1925 to an established annual best cultivar award. These beauties attract birds and hummingbirds with flowers ranging in color from blue, pink, lavender and white. This plant is toxic to humans and pets.

Delphiniums do well as border plants and in mass plantings. They are well-suited to woodlands, meadows and naturalized areas. They are often featured in cottage gardens.

Diseases, Insect Pests, and Other Plant Problems: Delphiniums are susceptible to powdery mildew, botrytis blight, leaf spots and crown rot. Plants in full sun generally show better resistance to powdery mildew. Crown rot will inevitably develop if plants are grown in poorly drained soils or planted too deep. Slugs and snails can do significant damage. Watch for aphids, leaf miners, stem borers and mites.