These are called Magic Fountains, D. elatum – they are the classic delphiniums. However, the D. chinensis are more popular because of the delicate blue hues. The ancient Greeks thought that the flower bud resembled a dolphin, hence the name Delphinium.
In Tudor England, the common name ‘larkspur’ referred to the supposed similarity of the flower to a lark’s claw. Modern delphiniums are hybrids. Breeders crossed species such as D. elatum from the Swiss Alps, D. cheilanthum, a dark blue Siberian species and the purple, hooded D. brunonianum from the Himalayas. The commonly grown modern Delphinium elatum type has evolved from these crosses, with the large forms we recognise today being developed in the early 20th century.
Are delphiniums perennials? They seem to be annuals here. Delphiniums perform best in a sunny, open site with fertile, well-manured soil.
Source: BBC Gardening