How to remove invasive buckthorn
Q. I heard buckthorn is an invasive plant. I want to remove it from my yard, but then what do I do with it? I don't want the seeds to germinate.
A. Buckthorn is a native to Europe and western Asia and is one of the most invasive plants in our area. It creates a dense thicket crowding out native plants.
Two forms of invasive buckthorn are common buckthorn (Rhamnus cathartica); and glossy buckthorn (Rhamnus frangula). Both were introduced as ornamental landscape plants but quickly invaded natural areas.
Buckthorns are known for prolific reproduction by seed, long distance dispersion by birds, and wide habitat tolerance. They have a long growing season, leafing out before native plants and retaining its leaves until late fall. They crowd out trees, shrubs, wildflowers and perennials.
Removing the buckthorn fruit first will reduce the seeds added to your soil each year. Look for clusters of round, shiny, black berries. Buckthorn seeds in your soil can continue to germinate for up to five years. Buckthorn management is a multiyear commitment.
After the fruit has been removed, work in an area less dense with buckthorn before moving to the more heavily infested areas. Monitor all areas where buckthorn has been removed for new plants.
Small plants or seedlings can be removed by hand. Small seedlings will not re-sprout. Use a hand tool to pull out the shrub. It's easier to remove by hand if the soil is moist. Always check with JULIE, an agency that locates underground utilities, before digging to ensure there are no buried electric and gas lines in the area. Dig before the plant produces seeds, usually summer through fall. Disturbed soil may result in increased seed germination.
Buckthorn plants 2 inches in diameter or larger are best controlled by cutting the stem at the soil surface and either covering or treating the stump to prevent re-sprouting. Nonchemical control options include covering the cut stump with a tin can or black plastic such as a Buckthorn Baggie. Use nails to affix the can or a tie to affix the black plastic. Leave it in place for one to two years.
Chemical control options for cut stumps include treating the stump immediately after cutting with an herbicide using a paint brush or a single use foam brush. Glyphosate, a nonselective systemic herbicide, can be used. Make sure the herbicide purchased contains at least 18% to 20% glyphosate. Use it undiluted. Be sure to read, understand and follow the label directions for proper use of the chemicals. Chemical treatment can be applied to cut stumps when the temperature is above freezing.
The most effective time to cut and treat the stumps is in late summer and throughout fall. The plants are slightly stressed and the sap is flowing back toward the roots. Apply on a calm day with no wind. The herbicide is less effective in May and June when the tree is in its growth stage.
The most effective way to remove all parts of buckthorn is with fire; however, it isn't permitted in any municipality. I consulted John McCabe, resource management director with the Forest Preserves of Cook County and a local arborist. If buckthorn plants contain seeds, bag and mark them as landscape waste and place them out with your trash rather than composting them. Landscape waste is banned from landfills in Illinois, so waste companies take these products to a composting facility. High temperatures are critical for the destruction of seeds. Check with your local municipality for disposal.
Now with all that open space, what is a good alternative to buckthorn? The Chicago Botanic Garden recommends speckled alder, American filbert, hornbeam and arborvitae!
- Terri Passolt
• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 on Wednesdays or email northcookmg@gmail.com. Visit web.extension.illinois.edu/mg.