Invasive Plant – Wintercreeper!
Wintercreeper, or creeping euonymus, Euonymus fortunei, is an extremely aggressive evergreen perennial vine that was introduced as an ornamental ground cover in 1907. A member of the bittersweet family, it is native to China, Japan, and Korea. Wintercreeper is classified as “Invasive” by the Ohio Invasive Plant Council. It is sometimes called the “kudzu of the north”!
Wintercreeper is now pervasive throughout Central Ohio and the eastern half of the U.S., in public parks and private residences as well. Open areas in forests caused by wind, insects or fire are especially vulnerable to invasion. The nursery trade is still selling it, especially cultivated variants. As is true for many invasive plants, wintercreeper can be attractive, with its year-round deep green color!
Wintercreeper, as the name implies, rapidly spreads along the ground, forming a thick cover which displaces herbaceous plants and seedlings, depleting the soil of moisture and nutrients, sometimes even forming small shrubs. The mat of vines can become so thick that nothing else, even tree seedlings, can grow up through it. The vine easily climbs trees high into the canopy by clinging to the bark, shading the lower limbs as well, sometimes killing the tree. It can tolerate a broad range of environmental conditions ranging from full sun to deep shade, acidic to basic and low nutrient soils. It does not grow well in heavy wet soils.
Euonymus fortunei stems are green when young, becoming light gray and corky with age. The leaves are opposite, glossy, dark green, oval, slightly toothed, with light-colored veins, about 1-2.5 inches long. Flowers are small and greenish with five petals on long branched stalks. Fruits are small, round pink-red capsules that split open to expose seeds with red-orange covering.
Wintercreeper spreads by seed that is dispersed by birds and other wildlife. It can be spread long distances by streams and other bodies of water. The vine can only produce seeds when it climbs off the ground. Local spread is by vigorous vegetative growth, with frequent rooting along the vine which keeps establishing a new plant.
Wintercreeper is sometimes confused with Japanese honeysuckle and common periwinkle – Vinca minor. However, the edge of the periwinkle leaves are smooth, unlike wintercreeper.
Prevention and Control
Most importantly, DO NOT plant wintercreeper! A variety of mechanical and chemical methods are available for its management, including hand pulling, cutting and application of systemic herbicides.
A combination of methods often yields the best results and may reduce potential impacts to native plants, animals and other non-targeted species. The method you select depends on the extent and type of infestation, the amount of native vegetation on the site, and the time, labor, and other resources available to you.
The vines along the ground can be pulled by hand, especially when the ground is wet, as in the early spring and late fall. Masses of vine can be rolled up into a ball, and when dry are easily burned! Vines climbing trees or buildings should be a high priority to stop the formation and spread of seeds, and are best controlled by both cutting the vine near the ground, followed by immediately applying concentrated systemic herbicide to the cut stump. For large infestations spanning extensive areas of ground, a foliar herbicide with 1-3% glyphosate may be the best choice rather than manual or mechanical means, which could result in soil disturbance.
Please refer to the next section for more detailed information on treating wintercreeper.
Controlling Wintercreeper (Euonymus fortunei)
The first step for control of wintercreeper is to cut vines that are climbing trees or structures, otherwise they will produce berries that are then dispersed by birds and other wildlife. Small vines can simply be cut at the ground. For large vines, cut by removing a section of the climbing vine with loppers, a saw, or hatchet. To prevent damage to trees, try to avoid cutting into the bark when cutting the climbing vines. Once cut, it is not necessary to remove climbing vines from trees. Especially for larger vines, avoid pulling to avoid risk of injury or property damage due to falling limbs and heavy vines. For mats of vines on the ground, start at the edge of the wintercreeper area and pull the vines gently and slowly so the roots are pulled up with the vine. You can roll up the vines as you work, ending with a large ball of vines which should be removed from site and destroyed, ideally by burning. If burning is not an option, the material can be bagged in thick plastic, solarized to dry it out, and thrown away as solid waste rather than composted or left in place. It is important that pulled vines are not left in contact with the ground otherwise they will re-root and start growing again. Pulling is easiest when the ground is not frozen and is somewhat moist but can be done most times of year. There will be resprouting from underground stems; this new growth will need to be pulled repeatedly throughout the growing season over the course of multiple years to eradicate.
Sheet mulching (smothering) wintercreeper
Place pieces of overlapping cardboard over the wintercreeper vines growing along the ground, making sure the cardboard extends 6-12 inches beyond the edge of the area of infestation. Cover the cardboard with at least 6 inches of leaf and/or wood mulch. The mulch must stay in place for at least two growing seasons to kill the plants below. To increase effectiveness, continue to layer cardboard and mulch until the pile is 12 inches deep. Cutting the plants with a weed whacker before adding cardboard and mulch may increase effectiveness. Note that any other plants under the mulch will also be smothered and die. The mulching method is not ideal for areas under trees, as this may also cause tree roots to smother.
Cut stem treatment
For larger climbing vines of wintercreeper (>1/4 inch diameter), cut the vines as indicated above and immediately treat the cut stem with glyphosate (sold as Roundup, Drexel Imitator Plus, Glystar Plus, Compare-N-Save Grass & Weed Killer Concentrate, 41% Glyphosate, and many other trade names). Always read and follow the product label, which will include the dilution rate to use for cut surface treatment (e.g.) stump treatment (e.g. Drexel Imitator Plus, which has 41% active ingredient, is to be used full strength or diluted 1:1 with water for cut surface treatments). No surfactant is needed for cut stem treatments. Stems can be cut and treated whenever temperatures are above freezing, EXCEPT for during spring (April-May) when rising sap may prevent the uptake of herbicide through the cut. Check for resprouts or new growth from the base of the cut vine and control by repeated pulling or foliar herbicide spray (see below).
Foliar herbicide treatment
Vines and leaves of wintercreeper growing along the ground can be sprayed with a triclopyr solution (sold as Garlon 3a, Triclopyr 3, Brush Killer Plus, Remedy Ultra, Triclopyr 4, Garlon 4 Ultra, Vastlan and many other trade names) which is generally more effective than glyphosate for foliar treatment of wintercreeper. Always read and follow the product label, which will specify the dilution rate to use for foliar treatment; the recommended dilution rate will depend on which product you use (e.g., for the full-strength product Triclopyr 3, use a 3% dilution rate based on the label information). Because of the wintercreeper’s waxy leaf cuticle, it is recommended to add 0.5% non-ionic surfactant with the option to also add 1% methylated seed oil (or bean oil) to help the herbicide penetrate the leaf. Spray on days when the high temperature exceeds 40 degrees F, winds are less than 5 mph, and leaves are dry. Spraying in late fall (mid-October to late November) or early spring (February to mid-March) when native plants are still dormant will minimize non-target damage. Spraying during times of drought may decrease the uptake of chemical and reduce effectiveness, and in sandy soils tree species can be affected. Because wintercreeper can grow in multiple dense layers, the first foliar spray may not reach all of the leaves. One solution is to use a string trimmer (weed whacker) to remove the top layer of leaves to expose the bottom layer and then foliar spray. A second option is to do a follow up foliar spray a month or two after the initial treatment once the top layer has died and exposed the layer beneath. Treated areas should be checked for resprouts or new growth in the next two growing seasons with repeated spot treatments (or hand pulling of small patches) as needed until the infestation is gone. For chemical control near waterways and/or where surface runoff into waterways is a concern, you are required to select aquatic label formulations of herbicides and adjuvants.
The information in this section is provided by Bloomington Urban Woodlands Project (BUWP) and Monroe County (Indiana) – “Identify and Reduce Invasive Species” (MC-IRIS) for the education of landowners in Monroe County, December 2023. If you choose to use herbicide, neither BUWP nor MC-IRIS are responsible for any injuries or damage caused by such use. Bloomington Urban Woodlands Project.
Other information sources in this article include:
The Plant Conservation Alliance, Invasive.org, Bureau of Land Management, U.S. Dept of the Interior, December 2023.
Nathan Johnson, Ohio Environmental Council, “IInvasive.orgnvasive Wintercreeper (Euonymous fortunei), March 2018