Japanese Honeysuckle - An Eastern Asia Invader

Japanese honeysuckle (Lonicera japonica Thunb.) is a great example of an ornamental plant brought into the United States with all good intentions; however, like many introduced plant species, it should have stayed home in its native land. A native of eastern Asia, Japanese honeysuckle is believed to have been introduced in Long Island, New York in 1862. Since that time, it has spread throughout the eastern United States and has subsequently taken up home in areas westward, including the nation’s midsection. In Missouri, it is now scattered around the state.

Dense thicket of Japanese honeysuckle on waste ground

Besides serving ornamental purposes, the plant has been used for erosion control and wildlife food and habitat. As an ornamental plant, its purpose in the landscape has been its utility as a ground cover. The rapid growth of this perennial vine would lend itself perfectly as a plant that would serve a great use in areas with erosion problems that need a quick and stable ground cover. So, what is the problem with Japanese honeysuckle since it has all of these valuable qualities?

It’s considered a weed by anyone who has watched its aggressive growth habit take over a landscape in a relatively short time. Its twining vines can literally girdle the trunks of shrubs and trees, while at the same time engulf and choke out desirable landscape plantings. It is able to reproduce by several means. Vegetatively, it takes root along the soil surface at its nodes or where the leaves join the stems. It also produces underground rhizomes, which can give way to new sprouts that form local colonies. The many seeds produced in its berries are consumed by birds and passed over greater distances. It grows at its greatest rate in open, sunny areas; any shaded areas that have been modified to increase sun exposure can quickly become invaded if Japanese honeysuckle was present in relatively small densities. Like many non-native plants in the United States, Japanese honeysuckle has very few natural enemies that help to keep it in check. Insects and disease pathogens that would normally infest the plant in its native land and help to inhibit its growth simply aren’t present at all, or they don’t exist in sufficient populations in this country.

Japanese honeysuckle running along the soil surface

What does Japanese honeysuckle look like? The young stems of this vine are often reddish-brown in color and covered with hair. Older, mature stems become woody, hollow and have peeling bark. The leaves are simple-oval to oblong in shape-range in length from 1.5 to 3 inches and occur oppositely along the stems. During mild winters, the leaves may persist year-round. The flowers are a striking feature of Japanese honeysuckle. They may be either creamy white or yellow and are extremely fragrant. They will typically appear during early May and are produced throughout the summer. The fruit is a black berry that contains many seeds. For photos of Japanese honeysuckle, see http://www.psu.missouri.edu/fishel/japanese_honeysuckle.htm.

How is this weed controlled? The most effective means is to not introduce it into the landscape in the first place. Small populations can be controlled by hand by digging them out with a shovel. Remember, it does have the reproductive underground rhizomes, so those should be removed as well. With herbicides, there are several products available at the lawn and garden supplier. Some of the products containing various combinations of 2,4-D and dicamba and used for control of broadleaf such as dandelions in the lawn will list Japanese honeysuckle on their labels. There are also products that contain triclopyr or glyphosate labeled for Japanese honeysuckle control. Regardless of product choice, remember that this weed is in a different league than those broadleaf weeds that are controlled in the landscape with relative ease. Likely, several applications will be necessary and one’s patience will be sharply tested. A common misconception with perennial weed control is that the best and easiest time to control these plants is in the spring or summer. Actually, an early fall application will generally provide the best results in taking a perennial weed such as Japanese honeysuckle out of the landscape. The reason for this is that perennial plants are actively transporting food reserves to their root systems in preparation for the coming winter. Because of this, herbicides applied at this time will be carried along with the reserves downward into the plants’ roots, providing a more effective kill.

If you aren’t sure of the positive identity of Japanese honeysuckle or other pests that you feel are causing problems in your landscape, submit a sample to the MU Extension Plant Diagnostic Clinic. For a nominal charge, the Clinic has specialists who can provide accurate identification and proper control measures. The Clinic may be contacted directly by calling 573-882-3019 or on-line at http://agebb.missouri.edu/pdc/.

Fred Fishel, Extension Pest Management/Pesticide Training Coordinator, UMC (573) 884-6361