Japanese Honeysuckle
Lonicera japonica
Honeysuckle family (Caprifoliaceae)

Description: This perennial vine becomes woody with age and can reach 60' in length. Japanese Honeysuckle can climb adjacent woody vegetation, otherwise it has a tendency to sprawl across the ground in disorderly heaps. The young stems are green, pubescent, and terete, becoming purplish brown and more glabrous with age. The opposite leaves are up to 3" long and 2" across. They are oval or ovate, smooth along their margins, and evergreen. Young leaves are somewhat pubescent and ciliate, while older leaves are more glabrous. Each leaf has a short petiole that is also pubescent while it is young.

Flowers develop from axils of the leaves either individually or in pairs (usually the latter); they have short pedicels. Each flower is about 1–1" long, consisting of a corolla with well-defined upper and lower lips, 5 strongly exerted white stamens, a pistil with a strongly exerted white style, and a pubescent green calyx that is much shorter than the corolla. The tip of each style has a globular green stigma. The corolla is initially white, but it becomes yellowish tan with age. It has a long upper lip that curls upward and terminates into 4 narrow lobes, and a long lower lip that curls downward and terminates into a single narrow lobe. The narrowly tubular base of the corolla is finely pubescent along its outer surface. Underneath each flower, there is a pair of leafy bracts; each bract is up to 2" long, ovate, and slightly pubescent. The blooming period usually occurs during the summer and lasts about 2 months. The flowers have a delightful honeysuckle fragrance that is quite strong. Each flower is replaced by a black berry about " across that contains 2-3 seeds. The seeds are compressed (flattened) and ovoid in shape. The root system produces rhizomes that enable this plant to spread vegetatively.

Cultivation: The preference is partial sun, moist to mesic conditions, and a fertile loam to support the rampant growth. This vine is very aggressive; it can easily smother shrubs and small trees.

Range & Habitat: The non-native Japanese Honeysuckle is common in southern Illinois, occasional to locally common in NE and east-central Illinois, and uncommon or absent elsewhere. It was introduced into the United States from east Asia as an ornamental vine. Habitats include floodplain woodlands, thickets, seeps, limestone glades, power-line clearances in woodland areas, semi-shaded areas along roadsides and railroads, and edges of yards. Because of the attractive flowers, Japanese Honeysuckle is often cultivated in residential areas. This vine occurs in both disturbed and higher quality natural areas, and it has the capacity to displace many native species of plants.

Faunal Associations: The nectar of the flowers attracts Ruby-Throated Hummingbirds, swallowtails and other butterflies, and Sphinx moths (including the Hummingbird Clearwing, Hemaris thysbe). Moth larvae, aphids, and other insects are known to feed on the foliage and other parts of native honeysuckle vines (Lonicera spp.), although it is unclear to what extent they also feed on Japanese Honeysuckle. Two polyphagous leafhoppers, Empoasca chelata and Empoasca recurvata, are known to feed on this introduced vine, however (Dmitriev & Dietrich, 2010). The foliage of Japanese Honeysuckle is eaten by many mammalian herbivores, including the Cottontail Rabbit and White-Tailed Deer. Its evergreen leaves are especially important to them during the winter, when other sources of food are more scarce. Various upland gamebirds and songbirds occasionally eat the berries, including the Wild Turkey, Bobwhite, Eastern Bluebird, Purple Finch, Eastern Goldfinch, Slate-Colored Junco, and Hermit Thrush. These birds distribute the seeds far and wide. Dense tangles of this leafy vine help to provide cover for various mammals and nesting habitat for some species of songbirds.

Photographic Location: Edge of a yard in Urbana, Illinois, where the vine smothered a shrub.

Comments: While the flowers and foliage are quite attractive, Japanese Honeysuckle is one of the worst invaders of open woodland areas and thickets. On the positive side, it is moderately valuable to various mammals and birds. It is easy to distinguish Japanese Honeysuckle from other Lonicera spp. (honeysuckles) in Illinois, as the latter are either shrubs or much shorter vines. The branches of other honeysuckle vines terminate in small clusters or interrupted spikes of flowers. The terminal leaves (or bracts) below their inflorescences surround the stems and merge together (they are connate). In contrast, Japanese Honeysuckle usually produces axillary flowers. Japanese Honeysuckle can also be distinguished by its black berries, while the berries of other honeysuckle vines in Illinois are orange to red.