CLEVELAND, Ohio -- Last week's gardening column on the my years-long battle with invasive fish mint sparked a lot of interest and pleas for help.
Some readers sent emails with nothing but subject lines, like Laura from Kent, who wrote, "I have a river bank of knotweed, help!" Readers have spent years battling lesser celandine, buttercups, creeping Charlie, and mock strawberry in their gardens and lawns.
And for good reason. Invasive plants not only overrun garden beds; they are also one of the most persistent threats to Northeast Ohio's natural areas. From aggressive groundcovers like fish mint (Houttuynia cordata) and periwinkle (Vinca minor) to invasive grasses and even trees, managing these plants correctly is critical to protecting native ecosystems, as well as your lower back, knees, and wallet. Successful removal starts with knowing your enemy and then choosing the right strategy.
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For example, Vinca may look harmless with its glossy green leaves and pretty violet flowers, but it's a tough, spreading groundcover that quickly overruns native species. Like many invasive groundcovers, it forms dense mats that block sunlight, suppress wildflowers, and disrupt local habitats. It spreads mainly by trailing stems that root wherever they touch soil. Hand-pulling can work for small patches, but it requires complete removal of stems and rooted nodes. Multiple sessions are often needed over several years.
And hand-pulling invasive vines and groundcovers isn't just hard work, sometimes it can do harm than good, damaging the soil or promoting regrowth from remaining roots. The Pennsylvania Department of Conservation and Natural Resources (DCNR) has excellent plant-specific guidance on its website, covering not only vines and groundcovers, but also invasive trees, shrubs, and grasses. Their fact sheets outline the safest and most effective strategies for each plant. While my nemesis fish mint is not included, many common Northeast Ohio enemies are listed.
When mechanical pulling methods aren't enough, chemical control (meaning herbicides) may be the only reliable method. According to the Cleveland Metroparks' Invasive Plant Management guide, they use targeted application of glyphosate-based herbicides for controlling invasive groundcovers.
Many home gardeners avoid herbicides, while others see them as a necessary tool in the gardening toolbox, and as noted by the Metroparks, sometimes the only effective one when dealing with a large invasive plant problem. Of course, herbicides should always be used according to label directions and with proper protective gear.
Glyphosate, the recommended herbicide for many invasive plants, can be especially confusing. It was once synonymous with Roundup, but many current Roundup products no longer contain glyphosate as the active ingredient. Herbicides should be chosen based on expert advice, like that in the Pennsylvania DCNR fact sheets, and the herbicide name and concentration on the label should match the herbicide recommended for the plant you are combating.
A common gardening myth is that household cleaners like vinegar, salt, or borax offer a "natural" alternative to herbicides. In reality, these substances can damage soil, kill beneficial plants and microbes, and disrupt surrounding ecosystems. Worse, they rarely kill invasive plants at the root, meaning regrowth is inevitable. Not only are they ineffective for systemic plants like Vinca, they may pose environmental risks when used outdoors.
Every invasive plant requires a different removal strategy. Pulling may work for shallow-rooted groundcovers like Vinca and pachysandra (Pachysandra terminalis), but it requires several growing seasons to eradicate and landfill disposal of the removed plant material. For other vines, like the dreaded knotweed (Fallopia japonica) and kudzu (Pueraria montana), as well as many trees and grasses, herbicides are the only effective option and may require professional help to truly manage. While this news can be very discouraging to home gardeners like Laura from Kent struggling with a riverbank of knotweed, some invasive plants are a bigger problem than home gardeners can tackle on their and require coordinated, regional efforts for effective control.
For more information on invasive plant management, the Pennsylvania DCNR's Invasive Plant Fact Sheets (available at https://www.pa.gov/agencies/dcnr/conservation/wild-plants/invasive-plants/invasive-plant-fact-sheets.html) and Cleveland Metroparks' Invasive Plant Management guide (available at https://www.clevelandmetroparks.com/about/conservation/resource-management/invasive-plant-management) are essential tools for local gardeners. By following science-based methods, you can play an active role in preserving Northeast Ohio's native biodiversity.