Larkspur, in botany, the popular name for species of Delphinium, a genus of hardy herbaceous plants belonging to the natural order Ranunculaceae (q.v.). They are of erect branching habit, with the flowers in terminal racemes, often of considerable length. Blue is the predominating colour, but purple, pink, yellow (D. Zalil or sulphureum), scarlet (D. cardinale) and white also occur; the “spur” is produced by the elongation of the upper sepal. The field or rocket larkspur (D. Ajacis), the branching larkspur (D. consolida), D. cardiopetalum and their varieties, are charming annuals; height about 18 in. The spotted larkspur (D. requienii) and a few others are biennials. The perennial larkspurs, however, are the most gorgeous of the family. There are numerous species of this group, natives of the old and new worlds, and a great number of varieties, raised chiefly from D. exaltatum, D. formosum and D. grandiflorum. Members of this group vary from 2 ft. to 6 ft. in height.
The larkspurs are of easy cultivation, either in beds or herbaceous borders; the soil should be deeply dug and manured. The annual varieties are best sown early in April, where they are intended to flower, and suitably thinned out as growth is made. The perennial kinds are increased by the division of existing plants in spring, or by cuttings taken in spring or autumn and rooted in pots in cold frames. The varieties cannot be perpetuated with certainty by seed. Seed is the most popular means, however, of raising larkspurs in the majority of gardens, and is suitable for all ordinary purposes; it should be sown as soon as gathered, preferably in rows in nursery beds, and the young plants transplanted when ready. They should be fit for the borders in the spring of the following year, and if strong, should be planted in groups about 3 ft. apart. Delphiniums require exposure to light and air. Given plenty of space in a rich soil, the plants rarely require to be staked except in windy localities.
