DELPHINIUM

The perennial varieties for herbaceous borders range in height from 3 ft. 6 in. to 7 ft., often with flower spikes 3 ft. or more in length. Planting times are August to mid-October or during February and March. An open position, away from trees, walls or buildings is essential. Delphiniums only do really well on a deeply-worked, moisture-retaining soil. On very dry soils the plants will be disappointing unless steps are taken before planting to work in plenty of humus-forming material. Hop manure, peat, compost, wool shoddy, leaf mould or well-rotted farmyard manure should be freely mixed with both top and bottom spits. Bonemeal is also helpful. Plant with the crown just below soil level, setting each plant 2 ft. apart.

Thin out the shoots in early spring so that one or two only are left. In the second and subsequent years more shoots can be left but the initial thinning is well worth while as it enables the delphinium to build up a good root system, resulting in fine spikes on older plants. Stake the plants by the end of April, giving a first tie about 8 in. high and again as necessary. Mulching with damp peat, bark fibre, lawn mowings (provided they are not packed too close together) is desirable in a dry season, especially if the soil is on the light side. Do not mulch until the soil has warmed up and all weed seeds have been removed. May is a good month to mulch plants. Give 2 in. layers of mulching material and apply only when the soil is damp. Artificial watering must be undertaken in the absence of a mulch.

Choice of Varieties:. There are innumerable shades of blue, mauve, violet and purple which often defy either verbal or written descriptions. Nevertheless, all are beautiful and the majority sufficiently distinct from one another (not only in colour, but size of floret, length of spike etc.) to justify naming. Varieties growing over or under 51/2 ft. are noted. On light, sandy soils, delphiniums make taller plants but the heights will still be proportionate to those specified.

Agnes Brooks: very large gentian-blue florets with white eye. 6 ft. Alice Artindale: very double blue and mauve, flowers suggesting a ranunculus. Lasts very well either on the plant or when cut. Anne page: cornflower-blue. 6 ft.

Betty Baseley: dark blue with a black eye. Mildew-resistant. 4 ft. Betty Hay: pale sky-blue. Late flowering. Blackmore’s Glorious: mauve and pale blue with white eye.

Blue Brilliant: cobalt-blue.

Blue Tit: rich blue and indigo. Semi-dwarf habit, growing to about 4 ft. Mildew-resistant and quite happy in a windswept border. Boningale Glory: mauve and pale blue. Long spikes. Late. 6 ft. Bridesmaid: silvery-mauve with a white eye. Spikes hold well. Early. 6 ft. Cinderella: heliotrope with brown and heliotrope eye. Semi-dwarf growing to about 4 ft.

Crown Jewel: dark blue with white eye.

Daily Express: clear light blue. Flower spike over 3 ft long, holding remarkably well. Good constitution and gives plenty of cuttings. Mildew-resistant.

Everest: pure white. Late.

Florist’s Delight: gentian blue with brown eye. Excellent for cutting. Great Britain: very large florets, 4 in. in diameter, cobalt-violet with black eye. Mildew-resistant.

Guy Langdon: rich violet with violet-white eye. A 4 ft. spike on a 7 ft. plant. Harvest Moon: silvery-blue with a black eye. Excellent for cutting. Early. Jack Tar: deep cornflower-blue with black eye. Late. 5 ft. Janice: white. Semi-dwarf habit to about 4 ft. Late. Jennifer Langdon: pale blue and mauve with black eye. Very long-lasting. 5 ft.

Lady Eleanor: a very popular variety in the nineteen-thirties, still worth growing. Double blue and mauve florets (the inner petals waved) which drop rather quickly when cut. Exceptionally free-flowering and easy to propagate. Does well on dry soils. 6 ft.

Lorna: rich blue with dark-brown eye. Another old variety which should not be overlooked.

Melora: very pale mauve with white eye. 6 ft. Excellent for cutting and lasts well.

Minerva: violet with black and gold eye. 6 ft.

Mogul: rosy-purple. The very long spikes keep well when cut. 6y2 ft.Mrs Frank Bishop: gentian-blue with black eye. Lasts well. Late. Pastel Beauty: pastel pink with lilac and white eye. Royalist: deep blue, verging on purple. Stiff stems, resistant to bad weather. 6 ft.

Royal Prince: florets 3 ½ inches across, cobalt-blue with a black eye. Sea Mist: pale blue. Very late. Silver Moon: silvery-mauve with white eye. 5 ft. Supreme: violet and gentian-blue 5 ft. Swanlake: white. Very long-lasting. Early. Valentia: lobelia-blue and amethyst. Very long spikes. 6 ½ ft.W. B. Cranfield: blue and purple. Lasts well, even on dry soils. Now an ‘old stager’ but still worth a place. William Richards: electric-blue. Very long-lasting when cut. 5 ft.

Giant Pacifies. This American strain was developed to secure fixed colours which would come true from seed. Seed or plants to colour are available from British nurserymen and when well grown they are to some extent perennial. They give two crops of bloom but the individual florets lack the perfect placement on the spike of the latest British varieties.

The colours are, however, very rich and clear. The following strains can be recommended:

Galahad: white with a white eye.

King Arthur: plum-purple with a white eye.

Blue Jay: dark blue with a black eye.

Astolat and Elaine: embody various pink shades.

Belladonna Delphiniums:

These varieties bear single blooms, do not usually set seed and grow 3—4 ft. high. They flower twice and are long-lasting when cut. Bonita (vivid gentian-blue), Lamartine (dark blue), Pink Sensation (cerise-pink), Theodora (electric-blue) and Wendy (deep blue, flecked purple) are good varieties.

Annual Delphiniums:

Blue Butterfly (deep blue), Lavender Butterfly and White Butterfly grow to about 18 in. and may be treated as hardy annuals or sown in slight heat under glass.

Species Delphiniums:

Delphinium nudicaule (one of the parents of the hybrid Belladonna Pink Sensation) bears orange-scarlet flowers on branching stems in June. It grows to about 9 in. with a fleshy rootstock and is usually short-lived in gardens. This species has been used in America to develop a race of tuberous-rooted perennials 1—3 ft. high with pink, crimson and scarlet flowers. D. sulphureum and D.alil are both yellow, growing to about 2 ft., but are difficult to obtain.

Diseases and Pests:

Many of the more recent varieties are resistant to mildew but the disease can often be troublesome, especially if the plants have been allowed to become dry at the roots. Spraying with thiram, salicyanilide, Karathane or sulphur fungicides should help to keep the disease at bay. Black root rot which causes blackening of the roots, deterioration and final collapse of older plants, cannot be tackled by preventive or curative spraying. It probably arises from bad drainage and the presence of stagnant water inside the hollow stems and around the crowns of the plants. It is essential to cut down all stems and foliage to soil level in early October or as soon as they are obviously dead. Slugs can do considerable damage in January and February, especially during mild spells when the plants are just starting to ‘shoot’. A metal-dehyde preparation is the answer and this should be applied as necessary beginning in late autumn.

Propagation:

Cuttings are more economic and produce better plants than division. Young shoots about 4 in. long may be taken in March. Make the cut at the point where the shoot joins the crown. Cuttings should root in 5—6 weeks, if placed in pots or boxes in a cold frame which should be away from direct sunshine but in full light. John Innes Potting Compost is an ideal rooting medium.

Named delphiniums do not come true from seed any more than man-made varieties of lupins, michaelmas daises, chrysanthemums, carnations etc. but if seed is saved from the best modern varieties, some interesting seedlings should appear and possibly one or two which are improvements on existing kinds.

Delphinium seed loses its power of germination very quickly but stored in a refrigerator at about 40 degrees F. it will remain viable (capable of germination) for several years. Always ask your seedsman for refrigerated seed and if using your own, sow as soon as practicable after harvesting if you have no means of refrigeration. Sow in January or February in slight heat, in a cool greenhouse or cold frame in March or outdoors in late spring and early summer. John Innes Seed Compost is ideal. The seeds should be germinated in the dark and are usually through in about 14 days.

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