Invasive Exotic Plant Species: Honeysuckle (Lonicera spp.)

Background

Several species of Asian honeysuckle have been introduced in the United States for their ornamental and wildlife values. Honeysuckle is perhaps the most wide-spread exotic invasive in the U.S., now found in at least 38 states. The Asian honeysuckle produces abundant seeds which are dispersed by birds and other wildlife. It also spreads by sprouting from its roots. Because it tolerates shade from other plants, it grows in forest understories.

There are two forms of honeysuckle. Several species known collectively as bush honeysuckle (Lonicera spp.) grow in shrub form. The Japanese honeysuckle (Lonicera japonica) is a vine that covers the ground or climbs trees, eventually girdling and killing them.

Identification

Leaf – Leaves are oppositely arranged and variable in shape. They can be smooth to hairy. Bush honeysuckle leaves are persistent into winter while Japanese honeysuckle leaves are semi-evergreen.

Fruit – Fruits are berries about 1/5 to 1/2 inch in diameter. The Japanese honeysuckle fruits are black at maturity and bush honeysuckle fruits are orange to bright red. The fruits are usually persistent into winter.

Flower – Flowers are white, yellow, or pink and very fragrant.

Form – Forms are shrub, with some species reaching up to 20 feet in height, and a ground-sprawling or climbing vine (Japanese honeysuckle).

Note – Be careful not to mistake exotic bush honeysuckles for native honeysuckles such as northern bush honeysuckle (Diervilla lonicera) or American fly honeysuckle (Lonicera canadensis). Native types have solid rather than hollow stems and typically do not form extensive invasions.

Control

Smaller honeysuckle infestations can be controlled by hand-pulling individual plants. All rotos must be removed all roots, otherwise they will sprout prolifically. Repeated visits to the site, and follow-up hand-pulling, will be necessary for control.

In fire-adapted communities, prescribed fire can be used in the spring to top-kill honeysuckle. The roots will sprout, so continued use of fire will be necessary for control.

Herbicide control is possible in both foliar and cut-stump applications. Glyphosate has demonstrated success controlling both bush and Japanese honeysuckles and is available in a variety of formulations under different trade names. Since the amount of active ingredient (glyphosate) in different products varies considerably, the amount used should be carefully calibrated. Furthermore, glyphosate is a broad-spectrum, nonselective herbicide, so you must be careful to avoid contact with the foliage of non-target plants.

For foliar applications, a 2-percent solution of glyphosate in water with a surfactant is recommended. Plants should be sprayed between August and October. For a cut stump treatment, a 20-percent glyphosate solution in water with a surfactant should be applied between July and October.

Resources

Jackson, David R. 2005. Herbicides and forest vegetation management: Controlling unwanted trees, brush, and other competing forest vegetation. University Park, Pa.: Penn State College of Agricultural Sciences – Agricultural Research and Cooperative Extension. 31 p.

Miller, James H. 2003. Nonnative invasive plants of southern forests: a field guide for identification and control. General Technical Report SRS–62. Asheville, N.C.: U.S. Department of Agriculture, Forest Service, Southern Research Station. 93 p.

Swearingen, J., K. Reshetiloff, B. Slattery, and S. Zwicker. 2002. Plant Invaders of Mid-Atlantic Natural Areas. National Park Service and U.S. Fish & Wildlife Service, 82 pp.

Photo Credits: Chuck Bargeron, University of Georgia, www.forestryimages.org

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