Japanese honeysuckle was introduced in the United States in the 1800s. Intentionally spread as ground cover for erosion-prone slopes, the plant slowly escaped into the wild. Now naturalized throughout much of the eastern United States, honeysuckle chokes out native vegetation, disrupting ecological communities along the borders of forests. Killing honeysuckle vines isn't easy. Though the plant yields to overgrazing and fire, homeowners can attack the plant more selectively through its late-season growth.
Stop the spread of honeysuckle by mowing. Honeysuckle grows in the understory of forests at the edges of clearings and fields, spreading by seed and by underground runners. Frequent mowing prevents new vines from invading new ground.
Trim back honeysuckle growth in the fall to eliminate tendrils growing out of reach of chemical spray. Do not cut back the main plant. Pruning out other types of plants whose leaves could interfere with application isn't necessary if vines are treated in the fall after most other plants go dormant.
Mix Roundup by diluting with water according to the manufacturer's directions. Apply Roundup by spraying the honeysuckle's leaves thoroughly. Try to cover all surfaces of the leaves without over-application. Leaves should be wet with the chemical but need not be dripping. Honeysuckle leaves stay green and active--and vulnerable to the chemical treatment--well past the leaf drop of native species of plants. Spray before the first killing freeze. During genuinely cold weather the metabolism of honeysuckle drops, preventing the vine from absorbing the herbicide.
Apply a second round of spray to any leaves still green after 10 days. Test the vines after a few weeks by nicking the bark to look for green cambium tissue. If most of the vines are dead, remove them by pruning out sections a few at a time. Cut out short sections rather than trying to pull out long vines.
Check the area carefully for regrowth of honeysuckle vines the next spring. Spot spray any green growth. Control small areas of resurgent vines by grubbing out the roots with a mattock. Manually pruning any new vines down to ground level prevents seedlings or surviving roots from returning.