Family: Ranunculaceae

Mostly from the northern hemisphere, these hardy annuals, biennials and perennials are attractive plants, with tall spires of showy flow­ers. They are extremely popular in Europe and the United Kingdom as they do best in colder climates. In warm climates, few species are grown and it is preferable to treat them as annuals. In cool regions, they flower freely and last longer and are better treated as perennials. Delphiniums are known mostly by their beau­tiful, blue colour, though today many hybrids are available in red, pink, white and yellow. In the US, the Elatum Group is the most popular of the perennial delphiniums, with thick flower spikes in early summer to midsummer. There are tall, medium and small cultivars in this group. Delphiniums are useful for borders, pro­viding excellent cut flowers.

Species

D. elatum grows to 2 m (6 ft), with spikes of flowers in many colours, lasting from late spring through to autumn. Most garden del­phiniums and many cultivars have arisen from this species.

D. grandiflorum, butterfly delphi­nium, is an annual or perennial, to 45 cm (18 in), with white or blueish violet, early summer flowers. Specialist growers feature dozens of choice cultivars of delphinium.

Cultivation

Delphiniums require a rich soil, with added lime, and very good drainage. Propagate the Elatum Group delphiniums from sturdy basal cuttings in the spring. They are best rooted under glass with bottom heat. Seeds of annual delphiniums can be sown under glass in early spring and planted out in late spring. Space the tall hybrid varieties 50 cm (20 in) apart, with 50 cm (20 in) between rows, and the smaller types 30 cm (12 in) apart, with 40 cm (16 in) between rows. Once established, give regular applications of liquid fertilizer as they are heavy feeders and, during the flowering season, a heavy dressing of complete fertilizer. In the warm summer months, it is advisable to mulch the surface soil so that the roots are kept cool. Most of the taller types need individual stakes to protect them from wind damage.The new shoots are susceptible to attack by snails and slugs which should be removed.

Climate

Zone 3.