By Lisa Olson, Master Gardener Intern
Unless you live in New Mexico, Arizona, Nevada, or Hawaii, you are probably familiar with creeping charlie. According to the Minnesota Department of Natural Resources, it was brought to the United States as far back as 1672 from Europe to be used both as a source of food and for medicinal reasons. Before the widespread use of hops for making beer, creeping charlie was commonly used for that purpose, thus you may hear it referred to as “ale ivy” among other names, including “ground ivy” or “catsfoot.” A quick internet search will provide an abundance of websites claiming creeping charlie provides relief from a number of ailments from ringing in the ears to constipation to colic to bronchitis, and the list goes on and on. The internet, however, is lacking scientific research to support those claims. One thing that is certain is that creeping charlie is in the mint family. Being in the mint family, some fans of creeping charlie enjoy making tea from its leaves, or using them in salads, or cooking them similar to how spinach is prepared.
Rather than harvesting creeping charlie for its flavor profile, it is much more likely that you are not fond of the plant and spend an enormous amount of time and energy trying to eradicate it from your lawn or garden. There are a number of reasons creeping charlie is not welcome in a lawn or garden setting. Like the University of Minnesota Extension tells us, creeping charlie spreads or creeps across the top of the ground via surface roots or runners, called stolons, creating a dense carpet. The University of Michigan tells us that, similar to the runners above ground, creeping charlie has a rhizome root system that spreads horizontally below the ground. It can also spread by seed and even by small scraps of plant material dropped on the ground or left in the soil. It is a master at taking over areas where other plants are unsuccessful, like shady, moist areas, or where soil is compacted and only weeds tend to grow. Once established, it is very adaptable and has no problem creeping its way into sunny locations as well. It crowds out grasses and other desirable native plants.
In order to get creeping charlie back under control, it is important to recognize the plant in your yard. According to the University of Michigan, this herbaceous perennial can be recognized by its square-shaped stems, scalloped opposite leaves, and bilaterally symmetric purple flowers that bloom from April to June. You may notice the dense carpet of the leaves that the University of Illinois describes as somewhat kidney-shaped with rounded, toothed margins.
Before discussing how to get rid of creeping charlie, it is important to look at cultural control methods for how to prevent it from taking over in the first place; or at least how to create an environment that is not as conducive for its growth. One thing a gardener can do to prevent a creeping charlie takeover is to plant a shade tolerant grass in shady areas instead of a sun-loving Kentucky bluegrass, for example. The University of Wisconsin alternatively recommends foregoing grass in difficult shaded areas and instead planting other shade-loving plants like hostas, pachysandra, or vinca. Once alternative plants are established, newly introduced creeping charlie would have a more difficult time competing. Another cultural method to prevent or hinder the spread of creeping Charlie, would be to alter the growing conditions. Improving drainage or watering less makes the area less desirable for creeping charlie. The University of Minnesota also suggests reducing the amount of shade by trimming shrubs or pruning trees.
Mechanical methods of getting rid of creeping charlie include hand-pulling the plants. The University of Michigan reminds us that it will take diligence and patience to remove all of the plants. The most important thing to remember about this method is to get rid of every piece of the plant. Since any little piece left behind can sprout a new plant, it may take multiple seasons to clear out an area. With that in mind, mowing an area of creeping charlie can cause it to spread if the plant is mowed and the clippings are left behind. Remember to bag clippings when mowing an area that is infested with the plant. The Minnesota DNR also recommends setting the mower at a taller setting and fertilizing less to help choke out the creeping charlie.
Physical barriers, like edging, are not very effective in stopping the spread of creeping charlie. The stolons above ground and rhizomes below ground are very adept at finding their way over, under, or around barriers. However, if there is an area where you have decided to let creeping charlie live in your yard, a physical barrier will at least slow the spread as long as you are diligent about keeping it contained and removing any plants that make it past the barrier.
If none of the previous methods are reasonable or successful in your situation, it is time to consider herbicides, though, as the DNR states, herbicide control is challenging because creeping charlie can reestablish quickly after post-emergence treatment. The University of Minnesota makes the point that the timing of herbicide application makes a difference in its effectiveness. They recommend fall as the best time to apply it when the plant is taking up nutrients from the soil in order to survive winter. Purdue University adds that in the fall a very careful spot application is less likely to affect surrounding garden plants than in the spring when they are more actively growing. The next choice is spring when creeping charlie is actively growing if there are no surrounding plants or if they are shielded from the herbicide. The most effective herbicide against creeping charlie will contain the ingredient triclopyr. Also mentioned are 2,4-D and Dicamba. These are all selective broadleaf herbicides. This means that if you are treating creeping charlie in your lawn rather than in a garden, you do not need to worry about killing your lawn grasses as it will only kill the creeping charlie. Two – three applications per year should be sufficient to keep it under control if instructions are carefully followed, though the University of Wisconsin warns against applying Dicamba more than twice per year.
In the past, gardeners touted the use of Borax to treat creeping charlie. Research at the University of Wisconsin and Iowa State University have proven that it should not be used as broadleaf weed control against creeping charlie or any other weeds. It was found that even in small amounts, it is bad for the soil, providing an unfavorable growing environment for desirable plants.
If you have a large area where creeping charlie has completely taken over, you may want to consider one of these solutions. One method recommended by staff at the University of Michigan is called sheet composting, or lasagna composting. Layers of organic material are placed upon newspaper or cardboard to smother the creeping charlie and give you a fresh start. In a sunny location, the University of Minnesota recommends another natural method called solarization, where a sheet of plastic over the infested area for several months raises the temperature so that the creeping charlie can no longer survive. If you prefer a chemical alternative, the University of Minnesota suggests that if your lawn is at least 50% creeping charlie, you may want to apply a non-selective herbicide containing glyphosate, like Round-Up. It will kill all the vegetation. As with all chemicals, be sure to carefully follow the instructions to safely apply it and to see when it is safe for people and pets to enter the area and when you can re-seed the area.
Everyone’s situation is different, so it is important to consider all the different options for ridding your lawn and garden of creeping charlie. Everyone’s tolerance level is different, so one last thing to consider, but definitely not the least, is whether or not you can live with creeping charlie. Keeping our neighbors happy and controlling invasive weeds from spreading across the property line is important, but perhaps you have an area in your yard where you can allow creeping charlie to co-exist with you. It does provide a small benefit to pollinators, and the carpet of delicate purple flowers in the spring is a beautiful sight.