Battling Buckthorn

Wisconsin gardening comes with many obstacles: rabbits, deer, cold winters, and invasive non-native plant species. In the war against invasive plants, one of the worst enemies is Buckthorn, specifically Common Buckthorn (Rhamnus cathartica) and Glossy Buckthorn (Rhamnus frangula). Many times we’ll be at a customer's site and they want to know what the shrubs are creating a screen on the edge of their property. More often than not it's Buckthorn. Probably the worst example we've seen is someone's neighbor nicely pruned their Buckthorn and hung twinkling lights on it to enjoy from the deck. The tree was the source of loads of Buckthorn seedlings every year.

So what's the big deal about Buckthorn anyway? Europeans brought Buckthorn over to use for hedges and screening. It grows fast, has hardly any maintenance (unless you want to get rid of it), is easily sheared into a hedge, and rabbits and deer don't eat it. Unfortunately, it’s one of Wisconsin’s most damaging invasive plants. Read more about Glossy Buckthorn (

Problem #1: Buckthorn can quickly establish in full sun or shade – it doesn’t care. This aggressive plant will push out native plants, especially in the understory of forests where native plants don't receive enough sunlight to thrive. We have seen more Buckthorn popping as Ash trees are being lost to Emerald Ash Borer. The greedy buggers will gladly move into the spaces that Ash trees leave behind, swallowing up the landscape.

Problem #2: Female plants produce a multitude of berries. Birds will eat the fruit (even though they receive little nutritional value from them) and drop the seeds all over the place, perpetuating the spread. The species name of Common Buckthorn, cathartica, refers to how quickly the fruit and seeds go through the system of an animal. This way, the plant has ensured that it is quickly dispersed through the landscape. We call this the "evacuate" propagation method.

What To Do About Buckthorn?

The best time to battle Buckthorn is in late fall/early winter when it is easily recognizable.

This is because Buckthorn holds onto its green leaves much longer than other deciduous trees and shrubs. You'll also be able to identify it from the bold lenticels that create light-color, horizontal stripes on the dark stems. Larger, mature plants have long thorns on the branches. Scraping the bark reveals a bright orange/yellow color.

November is the perfect time to battle Buckthorn, whether in your yard or natural areas. Plants are moving water and nutrients into their roots for the winter, so herbicide applications are the most effective. Small seedlings and trees can be pulled by hand or using a weed wrench or the like.

Larger plants (1/2" caliper or more) that are too difficult to pull or too large to be sprayed, can be destroyed with the "cut and paint" method. This is easiest with two people doing the work: one person cuts the woody plants to the ground, and the other will come behind with a container containing the herbicide. Look for pesticides labeled for woody plants like Bonide Stump Out or glyphosate concentrates (like Roundup) mixed with a little water.

Be aware that some herbicides require a minimum temperature to be effective — check the labels. Use a sponge brush to apply the herbicide to the freshly cut stump. We like to add a little red food coloring to the mix so it's easy to tell which stumps have already been painted. Make sure to thoroughly coat the outer cambium ring (don't worry about the center on larger stumps). The sponge brush will give you more control so you don't accidentally drip onto desirable plants.

Burning the debris of branches you've cut down is the best way to destroy the seeds so they aren't spread to another area. If the task of removing large stands of Buckthorn is too daunting, contact a local landscaping company.

Plant Natives After Buckthorn Is Removed

When the Buckthorn is removed, you can begin replacing them with native plants. Re-establishing native plant cover will outcompete Buckthorn for light availability, which will help prevent reinvasion. Researchers at the University of Minnesota have seen that using native plants cuts the amount of returning Buckthorn in half over a few years. Scientists have also seen a 90% reduction in Buckthorn reinvasion when native trees and shrubs are planted. Read more about Managing Invasive Buckthorn (University of Minnesota, PDF).

Monitoring The Area For Re-growth

After removing Buckthorn and planting natives, yearly monitoring of the area for re-growth, and promptly removing shoots, will be important to keep this thug out. Making note of which plants did well can help you plan for future restoration efforts in your yard.

Buckthorn Replacement Plant Recommendations

There are many native grasses, groundcovers, perennials, shrubs, canopy, and understory trees that are excellent replacements for Buckthorn. It’s by no means a complete list, but a good sampling of options for a variety of conditions. Once you've won the battle, it'll be easier to spread the word about Buckthorn eradication to your neighbors, and we can finally win the war!