This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
The Larkspurs are erect leafy annual or perennial herbs. Leaves alternate, variously lobed or cut. Sepals 5, cohering below, the upper spurred behind. Petals 2 to 4, small, the two dorsal spurred within the spur of the sepal, the two lateral spur-less or absent. Carpels 1 to 5. Natives of the temperate zone of the northern hemisphere. Named from , a dolphin, from the form of the flowers. The species are very numerous and ornamental, but there are only about six in general cultivation.
The three following are the commonly cultivated annual species : 1. D. Ajacis. - A slightly-branched erect plant, about 18 inches high. This is the parent of the variously-coloured double and single 'Rocket Larkspurs' (fig. 14). It has long racemes and hairy follicles. South of Europe.
2. D. Consolida. - A more branched plant with shorter racemes and glabrous follicles. This is probably the parent of some of the garden varieties. S. Europe.
3. D. cardinale. - A beautiful scarlet-flowered species, 2 to 3 feet high. Native of California.
Among the perennial species we may enumerate : 4. D. elatum (fig. 15). Bee Larkspur. - An erect plant, 5 or 6 feet high, with 5-lobed leaves and single or double blue flowers. From Siberia, flowering towards the end of Summer.,
Fig. 14. Delphinium Ajacis. (1/4 nat. size.)
5. D. nudicaule. - This is a very showy species, and still rather rare in gardens. It grows a foot or more high, with tripartite somewhat fleshy leaves; segments lobed or toothed.
Fig. 15. Delphinium elatum. (1/4 nat. size.)
Flowers bright red tinged with orange. A native of California, flowering in Summer.
6. D. grandiflorum. - Another species of Siberian origin. A rather smaller, branching plant. Flowers large, deep dark blue, produced all the Summer.
Besides the above species there are many very beautiful garden varieties of hybrid origin. Amongst the best are: formosum, bright blue and white; Hendersoni, bright blue; Hermann Stenger, blue and rose, double; grandiflorum album, white; and magnificum, intense blue.