Many people have resolved to grow Delphiniums after seeing a group of well-grown giants towering over their heads in a border owned by an experienced gardener. Spikes clothed with large flowers in white, blue, pink, mauve or purple – hardly any other border plant can catch the eye in quite the same way. You can, of course, achieve the same sort of results if you have the space, but tall Delphiniums are not easy plants to grow to perfection. You will need to ensure that the soil is fertile and well drained and planting should take place in spring. Strong canes will have to be inserted at an early stage and you must keep careful watch for slugs and powdery mildew. Water in dry weather. When the main
Flowering period: during June and July has passed, cut back the flowering stems to induce another flush of flowers in autumn. In late autumn cut the stems down to ground level. The plants will slowly deteriorate with age and there is nothing you can do about it. The answer is to lift the clumps in spring every few years and divide them, replanting only the most vigorous sections.
VARIETIES: The popular garden varieties have been derived from D. elatum and are placed in 3 groups. The Elatum group have the classical Delphinium shape and flower form, growing up to 8 ft tall with upright spikes bearing large flat flowers which may be semi-double or double. The tall ones (height 5-8 ft. Spacing 2.5 ft) include ‘Vespers’ (blue-mauve), ‘Butterball’ (cream) and ‘Mullion’ (blue). Amongst the dwarfs (height 3-4 1/2 ft. Spacing 1.5 ft) can be found ‘Mighty Atom’ (lilac), ‘Cinderella’ (purple) and ‘BlueTit’ (dark blue). The second major section of Delphiniums is the Belladonna group – height 3-4 ft. Spacing 1.5 ft. These slender plants produce branching flower-heads which bear cupped (not flat) blooms. Compared with the Elatum group, the flowers are smaller and more widespread – the popular varieties are ‘Pink Sensation’ (pink) and ‘Blue Bees’ (pale blue). The third section is the Pacific Giants group – tall and large flowered, they can be raised from seed but unfortunately live only for a few years. Buy a mixture or a named variety, such as ‘Galahad’ (white) or ‘King Arthur’ (purple).
SITE AND SOIL: Well-drained and fertile soil is necessary-thrives best in a sunny and sheltered situation.
D. elatum
Belladonna group
D. elatum
Pacific Giants group
PROPAGATION: Plant cuttings in April or divide clumps in spring. Sow Pacific Giants seeds under glass in early spring.