Bulletin #2528, Maine Invasive Plants: Japanese Honeysuckle, Lonicera japonica (Honeysuckle Family)
Developed by the Maine Natural Areas Program and University of Maine Cooperative Extension
Threats to Native Habitats
Japanese honeysuckle is most aggressive in partially shaded to open upland areas, such as forest edges, canopy gaps, and stream corridors. It is most damaging where there is other vegetation it can climb over. The thick growth of Japanese honeysuckle blocks sunlight and gradually smothers other plants. Native shrubs and small trees can also be killed or stunted by girdling when honeysuckle vines wrap tightly around the stems, preventing water from moving through the plants. Japanese honeysuckle is most obvious when climbing high up and over plants along edges, but it also creeps along the ground in shadier areas where growth is moderated by low light levels. When disturbances occur causing the canopy to open, Japanese honeysuckle responds with dense growth.
Japanese honeysuckle is a trailing woody vine that may grow as much as 30 feet in length. Young stems are typically covered with fine hairs; older stems become hollow and have brown bark that peels off in shreds. Leaves are opposite, oval-shaped, occasionally lobed, and about one to two inches long. Leaves may be evergreen to semi-evergreen depending on the severity of the winters where the plants are growing. Flowers are tubular or trumpet-shaped, creamy white to pink, and turn yellow with age. They occur in pairs from between the leaves, are fragrant, and bloom through most of the summer. The vines produce small, blackberries with few seeds that mature in early autumn. Japanese honeysuckle is distinguished from Maine’s two rare native vine honeysuckles (Lonicera dioica and L. sempervirens) by the leaves at the tip of the vine. On Japanese honeysuckle these leaves are separate, and on our native species, they are fused or united, forming a single leaf surrounding the stem.
Japanese honeysuckle colonizes disturbed areas including roadsides, open banks, old fields, forest edges, and managed forests. It is tolerant of a wide variety of soil conditions and is especially aggressive in disturbed bottomlands and floodplains. It invades native plant communities after natural or human disturbances such as windthrow, insect outbreaks, road building, and logging.
Japanese honeysuckle was originally introduced to North America in the 1800s as a horticultural ground cover. It is native to eastern Asia. It is currently found in most states in the south- and central-eastern parts of the U.S. As of 2003, this plant has been reported from only one island location in Maine. Severe winter temperatures may limit the spread of this species in northern latitudes.
Several effective mechanical and chemical methods of control are available. Selection of a control approach is determined by the extent of the infestation and available resources.
Manual and mechanical: For small patches, hand-pulling of vines and root systems may be effective. A hoe can be used to help free root systems. Hand-pulling is most effective on root systems when the soil is moist. Repeated removal may be necessary to prevent reestablishment.
Chemical: Herbicide may be applied by spray to leaves or in higher concentrations to stems. Both glyphosate and triclopyr herbicides have been used effectively on Japanese honeysuckle.
Following product directions, apply a 2.5 percent mixture of a glyphosate-based herbicide to leaves any time between spring and fall. Repeat applications may be needed. Treatment in the fall may help avoid damaging desirable native plants. Cut stems can be treated with 25 percent glyphosate or triclopyr mixture any time of year as long as the ground is not frozen. Use herbicides responsibly and follow the manufacturer’s directions. Contact the Maine Department of Agriculture for information on restrictions that apply to the use of herbicides. Consult a licensed herbicide applicator before applying herbicides over large areas.
Smith, C.L. Exotic Plant Guidelines. Raleigh, North Carolina: Department of Environmental and Natural Resources, Division of Parks and Recreation, 1998.
Bravo, M.A. “Japanese Honeysuckle: Lonicera japonica Thunb.” Weeds Gone Wild: Alien Plant Invaders of Natural Areas. Plant Conservation Alliance’s Alien Plant Working Group.
Josselyn Botanical Society. Checklist of the Vascular Plants of Maine, Third Revision. Orono, ME: Maine Agricultural and Forest Experiment Station Bulletin 844, 1995.
Gleason, H.A. and A. Cronquist. Manual of Vascular Plants of Northeastern United States and Adjacent Canada, Second Edition. New York: New York Botanical Garden, 1991.
For more information or for a more extensive list of references on invasive species contact:
Department of Conservation
#93 State House Station
Augusta, ME 04333-0093
University of Maine Cooperative Extension
495 College Avenue
Orono, ME 04469
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