Invasive Species Sheet - Japanese Honeysuckle

Invasive Species Identification Sheet

Japanese Honeysuckle (Lonicera japonica Thunb.)

- woody vine; stems twine over the ground and other plants; mature stems hollow
- leaves opposite, thickish, 1"-3" long with untoothed margins; slightly glossy on upper sides
- pairs of leaves never joined at their bases
- flowers grow on young branches in pairs in the leaf axils (where leaf stem attaches to vine)
- flowers fragrant; usually white; fade to yellow; flower tube almost 1" long
- 4 of the 5 petals continue to be joined together most of their length above the flower tube
- berries black to dark purple-black; with more than 1 seed; can persist in fall and winter

In northeastern USA, the black to purple-black berries and the absence of any pairs of joined leaves distinguish Japanese Honeysuckle from native, viney Honeysuckles. Japanese Honeysuckle vines leaf out early and continue to grow later in the fall than most native plants. The vigorous runners can grow 10' or more per year and root at the nodes in moist soil. The vines are deciduous, semi-evergreen, or evergreen depending on winter conditions (not evergreen beyond USDA Zone 7). Vines may be red-brown in color. They have tiny, persistent scales at the end of the previous year’s growth. The current year’s vine growth is hairy. Leaves are hairy on the back (use hand lens) except for the variety chinensis (P.W. Wats.) Baker, called “Chinese Honeysuckle,” which has reddish flowers, purple branchlets, and hairless, or nearly hairless, leaves that are purplish when young. Although Japanese Honeysuckle leaf margins are never toothed, early spring leaves may be lobed. Each pair of flowers grows off one stem (making 4 flowers and 2 flower stems for each pair of leaves).

Japanese Honeysuckle is spread by birds and small mammals. It grows best in open fields, forest openings, and other sunny, disturbed places. The dense tangling growth that can strangle small trees and shrubs is a significant problem in New Jersey and southward. In New England, it should be watched carefully where disturbances (e.g., logging) open the forest to sunlight.