Introduction to Invasive Plants of Ohio
Approximately one-fourth of the plant species known to occur in Ohio originate from other parts of the continent or the world. These species are commonly called non-native, exotic or alien because they were not known from Ohio prior to the time of substantial European settlement around 1750. Since these species are not native to Ohio, they lack the natural predators and diseases which control them in their native habitats. They are usually characterized by fast growth rates, high fruit production, rapid vegetative spread, and efficient seed dispersal and germination. They often tolerate a wide range of environmental conditions and are quick to colonize recently disturbed sites.
Some of Ohio's non-native plants arrived here by accident, while others were introduced for agriculture, erosion control, horticulture, forage crops, medicinal use, and food for wildlife. Some of these invasive non-native plants are commercially available, primarily as cultivars.
Most non-native plant species are not invasive in natural areas. Of the more than 700 nonnative plants in Ohio, fewer than 100 are known to be problems in natural areas. These fact sheets describe the most invasive non-native plant species which impact and degrade Ohio's woodlands, wetlands, prairies and other natural areas. These species threaten Ohio's native biological diversity by displacing native plant species altering the food web and displacing the wildlife that relies on native plants for food, shelter, and breeding sites.
Successful control of invasive plant species is a time, labor, and resource-intensive process. Prevention or control during the early stages of invasion is the best strategy. In areas where invasive plants are well established, multiple control strategies and follow-up treatments may be necessary. Specific treatment depends on the target species' biological characteristics and population size. Invasive plants can be controlled using biological, mechanical, or chemical methods. Biological control uses the natural enemies of the invasive plant species to reduce its population. This method requires research and experimentation before appropriate control agents can be released. For example, years of research were conducted before beetle and weevil species native to Europe were introduced in the Midwest to control purple loosestrife.
Mechanical control includes physical removal such as cutting, mowing, grazing, digging, or pulling plants. Some invasive species will quickly reestablish from root fragments, seed banks, or after extensive soil disturbance. Other mechanical controls imitate natural processes, such as altering water levels and prescribed burning. Manipulating water levels to control certain invasive wetland plants can work, but it may also harm non-target species or native communities. Prescribed fire is used by land managers in fire-adapted ecosystems. However, due to hazards and legal liabilities, prescribed fire is subject to federal, state and local regulations and may be difficult for private landowners to implement.
When other control methods are ineffective, the use of herbicides may often be the best recommendation. Systemic herbicides are frequently used to control invasive plants. They are applied to the above-ground part of the plant and are transported throughout the plant to the root system. Selective application methods include foliar spray or wicking, cut stump application, and basal bark application to standing shrubs and trees. Each technique minimizes the amount of herbicide used and strives to treat only the target plants, which is critical in natural areas. Depending on the herbicide used, cut stump and basal bark treatments can be used in the dormant season which reduces vegetation trampling. Foliar spray is done during the growing season, or occasionally on semi-evergreen or biennial rosettes when other species are still dormant but the temperature permits active photosynthesis.
Site characteristics, including soil types, surface and ground water, non-target vegetation, sensitive areas, and offtarget exposure should be considered before applying herbicides. The timing of application, including the season, weather conditions, and growth stage of the target species should also be considered. To be most effective, many herbicides require penetrating, wetting, or sticking agents (such as Penevator Basal Oil* or Nu-Film-PÂ®). Other factors to evaluate before choosing a herbicide include: the type and concentration of active ingredients, its toxicity and health effects, selectivity (whether it harms all plants or only certain kinds), how long it persists in the environment, whether it moves off target (through the roots, spray drift, or vapor), and whether it can be used over or near water. Only certain herbicides are approved for wetlands or aquatic habitats. The herbicide label provides most of this information. Land managers experienced in herbicide use are also valuable sources of information.
The herbicides named in these fact sheets are referenced by product brand names. This does not imply an endorsement of a particular manufacturer's product, but these names are more recognizable than the active ingredient. Label instructions should be followed carefully. Persons who apply herbicides for hire are required by Ohio law to be licensed by the Ohio Department of Agriculture, Division of Plant Industry. On public lands, only licensed applicators or trained servicemen, under the supervision of a licensed applicator, may apply herbicides. Some herbicides are classified as "restricted use" and require a license for purchase and use.
After intensive removal of invasive species, restoration of natural habitats through replanting with native species is often needed. Nurseries and horticultural professionals can assist with native plant restoration. Complete eradication of invasive non-native plants from a site may not be completely achieved, but it is possible to reduce infestations within native plant communities to a level which can be routinely maintained. Control of invasive plants is critical to the long-term protection of Ohio's natural areas and rare species.
Additional Information Sources
Hoffman, R. and K. Kearns, eds. 1997. Wisconsin Manual of Control Recommendations for Ecologically Invasive Plants. Bureau of Endangered Resources, Wisconsin Department of Natural Resources, P.O. Box 7921, Madison, WI 53707.
Illinois Nature Preserves Commission. 1990. Illinois Vegetation Management Manual. Vegetation Management Guidelines.
Ohio State University Extension. 1992. Applying Pesticides Correctly: A Guide for Private and Commercial Applicators. Bulletin 825. The Ohio State University Extension, Columbus, Ohio.
Ohio Department of Agriculture, Division of Plant Industry, 8995 East Main Street, Reynoldsburg, Ohio 43068-3399. (614) 728-6987.
Tennessee Exotic Pest Plant Council. 1996. Tennessee Exotic Plant Management Manual.
Virginia Department of Conservation and Recreation & Virginia Native Plant Society. Invasive Alien Plant Species of Virginia.
Text written by Jennifer Hillmer, Carrie Morrow, Sarena Selbo, Kathy Cochrane, and Jeff Johnson.
Fact Sheets reviewed by Jim Bissell, Michael Vincent, David Nolin, John Watts, Brian Parsons, Meg Benke, Ohio Nursery and Landscape Association board members, and Division of Natural Areas & Preserves staff.