This section is from the book "The Standard Cyclopedia Of Horticulture Vol2", by L. H. Bailey. See also: Western Garden Book: More than 8,000 Plants - The Right Plants for Your Climate - Tips from Western Garden Experts.
(Greek, a dolphin, from the resemblance of the flower). Ranunculaceae. Larkspur. A group of beautiful hardy plants grown in borders for their handsome spikes of flowers and stately stems of foliage. They are of great value for cut-flower purposes as the blooms keep well.
Annual or perennial, erect, branching herbs: leaves palmately lobed or divided: flowers large, irregular, in a showy raceme or panicle; sepals 5, petal-like, the posterior one prolonged into a spur; petals 2 or 4, small, the posterior ones spurred, the lateral ones small, if present; the few carpels always sessile, forming many-seeded follicles. Full double forms are very common in a number of the species (compare Figs. 1232, 1233). A. Gray, An attempt to distinguish between the American Delphiniums, Bot. Gaz. 12:49-54, 1887. E. Huth, Monographic der Gattung Delphinium, in Eng. Bot. Jahrb. 20:322-499, 1895. There are about 60 species, native of the north temperate zone, four of which are of much greater popularity than the others: the annual, D. Ajacis, and the perennials, D. grandi-florum, D. hybridum and D. formosum. The last three have been especially prolific in named garden varieties. See page 3568.
Some of the garden varieties of delphiniums are as follows: King of Delphiniums, semi-double, and Duke of Connaught, distinguished by a deep intense blue and conspicuous white center of the large singular flowers; Mme. Violet Geslin and Julia, cornflower-blue varieties with white eye; Amos Perry, a combination of rich rosy mauve, flushed with sky-blue; Lizzie and Rev. J. J. Stubbs, spikes of vivid azure around deep brown centers. Combinations of sky-blue, pink and lavender are striking characteristics of Diademe, Excelsior, Grille, Hallgarten, Libelle, Minerva, Niederwald and Seidenspinner, distinguished from each other by white, brown or black centers. The petals of Carmen are of deep gentian-blue and pink, surrounding a brown center; those of Lamartine and Musea, lavender-blue; and Felicite, sky-blue. - Of the perpetual-flowering Belladonna class, the trade offers the following named hybrids: Capri, clear sky-blue; Moer-heimeii, pure white; Nassau, Mr. Brunton and Persimmon variations in sky-blue and azure; while the light graceful spikes of Semiplenum and Grandiflora show a clear intense cornflower-blue. - Perfect double-flowering delphiniums, though very handsome, are shy seeders and a small percentage come true to color and variety.
They do not seem to share in the great popularity of the singles. Of the latter the old species D. chinense, D. Davidii, and the rather hard to handle but otherwise beautiful yellow D. Zalil, are well worth cultivating. (R. Rothe.)
Rocket and Candelabrum are names used to designate the forms of inflorescence in the two annual species. The "Rocket" or spike-like form is more commonly found in the Ajacis type, and the "Candelabrum," with a number of short spike-like heads of different heights, is found more often in Consohda.
Delphiniums thrive in any good garden soil, but are improved by a deep, rich sandy loam, exposed to the sun. Deep preparation of the soil is very important. The annuals are propagated from seed, which are very slow in germinating. In the warmer latitudes they may be sown in early fall and will then produce flowers early the next season; or they may be started indoors.
The perennials, may be propagated: (1) By root-division in the fall or spring. The large strong-growing species may be divided into a number of plants after growing in the flower-bed for several years. (2) By cuttings, about which J. B. Keller says: "Take a few cuttings from each plant in early spring, when growth is about 3 or 4 inches long, or else use the second growth, which has come after the flower-stems have been removed. Cuttings root readily in a shaded frame, no bottom heat being required, but an occasional sprinkling during dry and hot weather is necessary. When rooted they are treated like seedlings." (3) By seeds, started in the greenhouse or hotbed in March or even earlier. The young seedlings should be given plenty of room by transplanting as they grow, and may be set in the open garden by June. If started thus early they flower the first autumn. The seed may be planted in late spring or summer, care being taken to water well during dry weather, and flowers will come the next sum-,mer. To get the best results, the perennials should be transplanted every 2 or 3 years.
Two good crops of blossoms may be secured in one season by cutting away the flower-stems of the first crop as soon as the flowers have faded; of course no seeds will be produced in this way.
In most climates where they are grown the roots of the perennials are left unprotected, in the open garden, during the winter. This plan can be improved by giving the bed or border a good dressing of barnyard manure about the time the ground begins to freeze in the fall. This will greatly enrich the soil and also protect the underground buds during winter. A much better show of flowers will be the result. Because of their ability to use much fertility, it is well to spade in the manure instead of removing it in the spring. A top-dressing of manure near the plants in midsummer is used to aid in forcing the "fall" or second crop of flowers. This dressing conserves the soil-moisture, prevents weeds, and adds plant-food. Such applications of manure will make the plants more vigorous throughout. They will flower more profusely and, if desired, the roots can be divided much more freely.
Fig. 1231. Delphinium Ajacis. (X 1/2) a. Annuals: petals only 2, united: follicle 1.
Fig. 1231. An erect annual, about 18 in. high, with a few spreading branches: leaves of stem sessile, deeply cut into fine, linear segments; root-leaves similar, but short-petioled: flowers showy, blue or violet, varying to white, more numerous than in D. Consolida, in a spicate raceme; petals 2, united; calyx-spur about equaling the rest of the flower: follicle only 1, pubescent; seeds with wrinkled, broken ridges. May-Aug. Eu. R.H. 1893, p. 228. Same figure in S.H. 2:282. - The season of flowering is governed largely by the time of sowing the seeds. If sown in the fall, as may be done in warm climates, the plants will produce flowers by May or June. But if the seeds be sown in spring no flowers should be expected before July or Aug.