CAPRIFOLIACEAE (Honeysuckle Family)

Contributed by Alan Whittemore

Plants shrubs, small trees, lianas, or perennial herbs. Leaves opposite, simple or pinnately compound but infrequently lobed. Stipules absent or, if present, relatively inconspicuous and scalelike or glandular. Inflorescences consisting of solitary, paired, or densely clustered flowers in the leaf axils or of terminal clusters or panicles. Flowers perfect (in paniculate species, occasionally some of the marginal flowers sterile), epigynous. Calyces 5-lobed, actinomorphic, fused to the ovary, the tube sometimes extending slightly past the ovary, usually persistent at fruiting. Corollas 5-lobed, actinomorphic and funnelform to cup-shaped, bell-shaped, or saucer-shaped, or strongly zygomorphic and strongly 2-lipped, white, cream-colored, yellow, pink, or red. Stamens 5, the filaments distinct, attached to the base of the corolla. Anthers oblong to oblong-elliptic or nearly linear, attached above the base on the dorsal side. Pistil 1 per flower (but the ovaries of adjacent flowers sometimes fused), of 2–5 fused carpels. Ovary inferior, with 2–5 locules, the placentation axile. Style 1 per flower with the stigma capitate and sometimes shallowly 2–5-lobed or absent and the sessile stigma deeply 3–5-lobed (usually appearing as 3–5 separate stigmas). Ovules 1 to numerous per locule. Fruits berries or berrylike drupes with one to several seeds or seedlike stones. Fifteen genera, about 400 species, nearly worldwide, most diverse in temperate and montane regions.

Many species of Caprifoliaceae are popularly cultivated as ornamentals. In addition to the genera treated here, two groups of mostly Asian bush honeysuckles, Abelia R. Br. and Weigelia Schreb., are commonly seen in gardens. They differ from the genera present in the wild in Missouri by their sepals, which are large and prominent, and their fruits, which are dry and capsular.

The circumscription of Caprifoliaceae in the present treatment is the traditional one (Steyermark, 1963; Cronquist, 1981, 1991). However, phylogenetic studies in recent years have suggested that a broad renovation of familial limits in the order Dipsacales is necessary (Donoghue et al., 1992, 2001; Judd et al., 1994; Bell et al., 2001). Both morphological and molecular data provide evidence that the broad traditional circumscription of Caprifoliaceae does not accurately reflect the phylogeny of the group, because the core of the family (including the Missouri genera Lonicera, Symphoricarpos, and Triosteum) is more closely related to members of the Dipsacaceae and Valerianaceae than to other genera traditionally included in the family. The two Missouri genera with sessile stigmas and saucer- or cup-shaped corollas, Sambucus and Viburnum, along with three small herbaceous genera, Adoxa L., Sinadoxa C.Y. Wu, Z.L. Wu & R.F. Huang, and Tetradoxa C.Y. Wu, probably are better treated in a separate family, Adoxaceae. Some authors have gone so far as to submerge Dipsacaceae and Valerianaceae into a redefined Caprifoliaceae (Judd et al., 2002), but further details of familial limits within the order remain to be elucidated through broader taxon sampling and more detailed studies within the major branches of the overall phylogenetic tree.