Delphiniums are a beautiful addition to any garden, but those in cold regions should be grown in containers that can be brought inside during the winter or treated as annuals. They can survive in USDA Zones 3-7. These plants need well-drained soil and regular watering, about 2-3 inches per week, especially during dry spells. Their bright and full blooms come in shades of pink, white, blue, white and off-white and bloom in spring and summer. However, all parts of the Delphinium plant are poisonous if ingested.
Delphinium is a genus of about 250 species in the buttercup family, native to the Northern Hemisphere and high mountains in tropical Africa. The leaves are deeply lobed with 3-7 toothed, pointed lobes and the stem is topped with many flowers in shades of purple, blue, red, yellow or white. The flower has five petals that form a hollow shape with a spur at the end, which gives the plant its name. The seeds are small and shiny black. These plants are pollinated by butterflies and bumblebees and flower from late spring to late summer.
These popular perennials prefer full sun and slightly alkaline, well-drained soil. They are heavy feeders and require fertilization twice during the growing season. Some varieties may need staking. The Dwarf Delphinium grandiflorum "Blue Mirror" is a unique variety that grows under 1 foot tall and forms a low, bushy mound. It produces loose sprays of electric-blue flowers all summer long and is suitable for containers, rock gardens or as edging in sunny borders.