1. Lonicera L. (honeysuckle)

Plants shrubs or lianas. First-year twigs 1–2 mm thick, the pith solid or hollow. Winter buds more or less ovoid to conical, with 2 to several overlapping scales. Leaves sessile or with short, unwinged petioles, the uppermost leaves sometimes strongly perfoliate (fused at the base to form a single blade surrounding the stem). Stipules absent. Leaf blades simple, unlobed or in L. japonica the first leaves of the season sometimes irregularly lobed, elliptic to ovate, oblong, or oblanceolate, the margins entire. Flowers in pairs in the leaf axils, or in 1–4 whorls terminal on the branches, or in L. purpurea in 1 or 2 sessile pairs from buds on second-year branches, the individual flowers usually subtended by small, paired bractlets, the inflorescences subtended by bracts. Corollas 13–48 mm long, actinomorphic and narrowly tubular-funnelform or zygomorphic with spreading to recurved lobes, sometimes the lobes similar in size and sometimes shape but positioned zygomorphically, white, pink, yellow, orange, or red. Style 8–50 mm long. Fruits berries, more or less spherical (oblong-ellipsoid in L. purpusii), red, black, or rarely yellow at maturity. Seeds few, 2.5–6.0 mm long, oblong-ovate to oblong-elliptic in outline, sometimes irregularly so, often somewhat flattened, one or both sides sometimes slightly angled or with a pair of shallow longitudinal grooves, the surface smooth or more commonly with a minute network of low ridges, reddish brown to dark brown. About 180 species, North America, Europe, Asia.

Honeysuckles have long been very popular in horticulture, and numerous species and cultivars exist in cultivation. The plants are easy to grow, tolerant of difficult conditions, and their flowers are attractive and (in many species) fragrant. The berries attract birds in the autumn. However, some exotic species of Lonicera are very invasive in natural plant communities, and the genus includes two of the worst invasive exotics in Missouri, L. japonica and L. maackii.

In Missouri, two escaped taxa of shrubby honeysuckles exist that arose through past interspecific hybridization, but whose parents do not occur in the state. Because these fertile hybrids are not easily related to any of the other species in the state, they are accorded full treatments below.