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.
(after Diereville, a French surgeon, who took D. Lonicera to Europe early in the eighteenth century). Caprifoliaceae. Weigela. Ornamental deciduous shrubs, grown for their showy flowers appearing profusely in spring and early summer.
Leaves opposite, petioled or nearly sessile, serrate: flowers in 1- to several-flowered axillary cymes, often panicled at the end of the branches, yellowish white, pink or crimson, epigynous; calyx 5-toothed or 5-parted; corolla tubular or campanulate, 5-lobed, sometimes slightly 2-lipped; stamens 5; style slender with large capitate stigma; ovary inferior, elongated, 2-celled: fruit a slender, 2-valved caps, with numerous minute seeds. - About 10 species in E. Asia and N. Amer.
Diervillas are shrubs of spreading habit, with more or less arching branches, rather large leaves, and, especially the Asiatic species, with very showy flowers from pure white to dark crimson, appearing in spring. A very large number of hybrids between the different Asiatic species have been raised and have become great favorites in gardens on account of their profusely produced and delicately tinted flowers. The earliest to bloom are D. praecox and its hybrids and also D. florida variety venusta, which begin to flower in Massachusetts about the middle of May; the latest is D. rivularis. The American species are hardy North and prefer moist and partly shaded positions. Of the Asiatic species D. Middendorffiana is the hardiest, but rarely does well; it seems to grow best in humid sandy or peaty soil and in positions sheltered from strong winds; it dislikes hot and dry air; D. florida also is rather hardy and one of the handsomest species of the genus. The other Asiatic species require protection during the winter or sheltered positions. They thrive well in any humid garden soil.
Propagation is readily effected by greenwood cuttings or hardwood cuttings; the American species usually by suckers and by seeds sown in spring.
A. Flowers yellow, slightly 2-lipped, small, about 1/2in. long.
b. Leaves glabrous or nearly so.
(D. trifida, Moench. D. canadensis, Willd.). Shrub, to 3 ft.: branchlets nearly terete, glabrous: leaves distinctly petioled, ovate-oblong, acuminate, serrate, nearly glabrous, finely ciliate, 1 1/2-4 in. long: cymes usually 3-flowered; limb nearly equal to the tube: caps, about 1/3in.. long. June, July. Newfoundland to Sask., south to Ky. and N. C. B.M. 1796.
Shrub, to 5 ft.: branchlets quadrangular: leaves nearly sessile, ovate-lanceolate, serrate, nearly glabrous, of firmer texture, 2-6 in. long: cymes 3-7-flowered, often crowded into dense, terminal panicles; limb shorter than the tube: caps, about 1/2in.
Fig. 1263. Diervilla japonica. (X 1/3) long. June, July. N. C. and Tenn, to Ga. and Ala. G.C. III. 22:14; 42:427 - Hardy in Canada.
bb. Leaves, branchlets and infi. pubescent.
Shrub, to 6 ft.: leaves short-petioled, ovate to oblong-lanceolate, acuminate, truncate or cordate at the base, doubly serrate, pubescent on both sides, 1 1/2-3 1/2 in. long: cymes few- to many-fid., crowded into terminal panicles; limb of corolla about as long as tube: caps. 1/4in. long. July, Aug. N.C. to Tenn., Ga. and Ala. G.C. III. 38:339.
aa. Flowers showy, white, pink, or crimson, rarely yellowish.
b. Anthers not connected with each other. (Weigela.) c. Calyx-lobes lanceolate, connate to or nearly to the middle; stigma 2-lobed: seeds almost wingless.
(Weigela rosea, Lindl. W. amabilis, Hort. D. pauciflora, Carr.). Shrub, to 6 ft.: branchlets with 2 hairy stripes: leaves short-petioled or nearly sessile, elliptic or ovate-oblong to obovate, serrate, glabrous above except at the midrib, more or less pubescent or tomentose on the veins beneath, 2-4 in. long: calyx nearly glabrous, with lanceolate teeth; ovary slightly hairy; flowers 1-3, pale or deep rose, 1 1/4 in. long; corolla broadly funnel-shaped, abruptly narrowed below the middle. May, June. N. China. B.M. 4396. F.S. 3:211. B.H.1:577. Gt. 54, p. 86. R.H. 1849:381. H.F. 1854:21. V. 18:37. - This is one of the most cult, species, very free-flowering and rather hardy. variety alba, Moore. Flowers white, changing to light pink. R.H. 1861:331. variety venusta, Rehd.
Leaves smaller, usually obovate, 1 1/2 -2 1/2 in- long, usually nearly glabrous: flowers in dense clusters with small leaves at the base; corolla slender, about 1 1/2 in. long, rather gradually narrowed toward the base, lobes oval to oval-oblong, rosy pink. Korea, N. China. - Recently introduced; very floriferous, early and hardy.
Shrub, to 6 ft.: branchlets glabrous: leaves short-petioled, elliptic or elliptic-ovate, acuminate, serrate, hairy above, soft-pubescent below, 2-3 1/2 in. long: flowers clustered, 3-5, nodding; calyx with subulate lobes; ovary hairy; corolla abruptly narrowed below the middle, purplish pink or rose-carmine. Japan. May. Gt. 46:1441; 53, p. 522. R.H. 1905:314. - The earliest of all species to bloom; has given rise to a race of early-flowering hybrids as Avalanche, Gracieux, Vestale, Conquerant, Esperance, Seduction, which see under D. hybrida.
cc. Calyx-lobes linear, divided to the base: seeds winged: stigma capitate.
D. Plant nearly glabrous.
(D. grandiflora, Sieb. & Zucc. D. amabilis, Carr.). Shrub, 5-10 ft.: leaves rather large, obovate or elliptic, abruptly acuminate, crenately serrate, sparingly hairy on the veins beneath and on the petioles: flowers in 1-3-flowered, peduncled cymes; corolla broadly funnelform, abruptly narrowed below the middle, changing from whitish or pale pink to carmine. May, June. Japan. S.Z. 31. F.S. 8:855. H.U. 1:19. - Vigorously growing shrub, with large leaves and flowers, but less free-flowering, and the type not common in cultivation variety arborea, Rehd. (W. arborea grandiflora, Hort.). Flowers yellowish white, changing to pale rose; of vigorous growth.
dd. Plant more or less pubescent: corolla finely pubescent outside.