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Viburnum (the ancient Latin name). Caprifoliaceae. Ornamental woody plants grown for their attractive flowers, fruits, and foliage.
Deciduous or sometimes evergreen shrubs, rarely small trees, with opposite stipulate or exstipulate lvs.: fls. small, in terminal paniculate or mostly umbel-like cymes; calyx with 5 minute teeth; corolla rotate or campanulate, rarely tubular; stamens 5; ovary usually 1-loculed: fr. a drupe with a 1-seeded, usually compressed stone. In several species the marginal fls. of the cymes are sterile and radiate; such are V. macrocephalum, V. tomentosum, V. Opulus, V. americanum, V. Sargentii, and V. alnifolium, and of the 3 first-named garden forms are known with all fls. sterile and enlarged.—About 120 species in N. and Cent. Amer. and in the Old World from Eu. and N. Afr. to E. Asia, distributed as far south as Java. For a key to the 65 species known from E. Asia, see Rehder, The Viburnums of Eastern Asia, in Sargent, Trees and Shrubs, 2:105-116.
The viburnums are upright mostly rather large shrubs or sometimes small trees with usually medium-sized deciduous or evergreen foliage and white or sometimes pinkish flowers in showy flat clusters or sometimes in panicles, followed by berry-like subglobose to oblong, red, dark blue, or black fruits. The viburnums rank among the most valuable ornamental shrubs. Besides showy flowers and decorative fruits they possess handsome foliage which mostly assumes a bright fall coloring. The plants are of good compact habit. Most of the deciduous species are hardy North, but V. macrocephalum var. sterile and V. obovatum are tender; also V. tomentosum, V. Wrightii, V. theiferum, V. cotinifolium, V. nudum, and V. dilatatum are not quite hardy farther north than New England. Of the evergreen species, V. rhytidophyllum is the hardiest and at the same time one of the most distinct and handsomest species of the genus, with its bold foliage and the large clusters of flowers and fruits; it is hardy as far north as Massachusetts in favorable positions; also V. japonicum stands several degrees of frost, but cannot be relied on north of Philadelphia; V. odoratissimum and V. suspensum are still tenderer. The viburnums are well suited for borders of shrubberies or planting along roads, and the more showy ones are handsome as single specimens on the lawn. They are mostly medium-sized shrubs, 5-10 feet high, but V. Lentago, V. prunifolium, and V. rufidulum sometimes grow into small trees, 30 feet high, while V. acerifolium hardly reaches 5 feet. The most decorative in fruit are V. Opulus, V. dilatatum, and V. Wrightii, with scarlet or red berries which remain a long time on the branches. Besides the snowball forms, V. dilatatum, V. tomentosum, V. Sieboldii, V. prunifolium, V. rufidulum, V. venosum, and V. dentatum are very handsome in bloom. Varieties with all the flowers of the cymes sterile and enlarged are known in the case of V. Opulus, V. tomentosum, and V. macrocephalum, the common, the Japanese and the Chinese snowballs; all these are very showy. One of the most charming in bloom is V. Carlesii on account of its rather large pink-and-white and deliciously fragrant flowers which appear in dense clusters early in spring before or with the leaves; almost all other species bloom after the leaves. The foliage of most species turns purple or red in fall, that of V. Opulus, V. americanum, and V. acerifolium being especially brilliant. V. dilatatum assumes a dull yellow color. V. macrocephalum and V. Sieboldii keep the bright green of their foliage until late in autumn. The viburnums are not very particular as to soil and position, but most of them prefer a rather moist and sunny situation. Some, as V. acerifolium, V. Lantana, V. dilatatum, V. Tinus, V. pubescens, and V. prunifolium, grow well in drier places, while V. alnifolium and V. pauciflorum require shade and a porous soil of constant moisture. V. acerifolium does well under the shade of trees in rocky and rather dry soil. V. Tinus is often grown in pots and thrives in any good loamy and sandy soil. With a little heat it may be forced into bloom at any time in the winter; if not intended for forcing, it requires during the winter a temperature only a little above the freezing-point and even an occasional slight frost will not hurt it. The common and the Japanese snowball are also sometimes forced and require the same treatment in forcing as other hardy shrubs.
Propagation is by seeds sown in fall or stratified; also by greenwood cuttings under glass, especially V. tomentosum, V. macrocephalum, V. venosum, V. cassinoides, and the evergreen species; V. dentatum and V. Opulus and its allies grow readily from hardwood cuttings and all species can be increased by layers; grafting is also sometimes practised, and V. Opulus, V. dentatum, and V. Lantana are used as stock.
The familiar snowball is seriously attacked by aphids. Fortunately its place can be taken by a Japanese species that is even more satisfactory. (Fig. 3923.) The berries of its fertile type, V. tomentosum, are a brilliant scarlet, changing to black. The foliage of this snowball is also remarkably beautiful. The leaves are olive-green with brownish purple or bronzy margins, and their plicate character makes them very distinct and attractive. The bush is entirely free from insect pests. The single and double forms of the Japanese species differ as shown in Figs. 3922 and 3923. Unfortunately these "single" and "double" forms have been confused in many nurseries, and only the trained eye can tell them apart in the nursery row. The double or snowball type is, of course, the one destined to the greater popularity, though the single form is a shrub of great value, especially for large estates and parks. The double form is known to nurseries as V. plicatum, but its proper name is V. tomentosum var. plenum. While it is hardy in New England, it is not a shrub that can be transplanted as easily as many other species. Hence it should be transplanted every second year in the nursery until it is sold. The double form may be propagated by cuttings of half-ripened wood in close frames, or by layers, which in some soils would better remain two years. French nurserymen propagate it by layering. The layers seem to suffer from winter and, to be on the safe side, it is best to cover them well with moss or leaves when the ground is somewhat frozen, so that the frost may be kept in until spring. The clusters are about as big as oranges and pure white. They are in great demand for Decoration Day in New York. The single form, unlike the double, is easily transplanted. It is also readily propagated by layers or cuttings. Both kinds are hardy in the North and make compact bushes 6 to 8 feet high.
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