Nature Articles - Alien Invasion                                     

The Invasion Of The Wildland Weeds
By Tom Borgman, Land Management Technician

Native plants have evolved over the centuries to live in harmony with other native plants and animals. Together they create a balanced, diverse natural community where many species thrive.

Over the years, plants from around the world have been introduced for erosion control, wildlife foods, landscaping, forage crops, medicinal use or by accident. Most of these plants never stray from their intended locations, but those that do can present serious problems in natural habitats.

Invading plants can take over whole sections of forest, displacing native tree saplings, shrubs and wildflowers. A wetland invaded by the non-native purple loosestrife will leave little room for the original native species. Native purple coneflowers, blazing stars and black-eyed Susans in a prairie can become overwhelmed by aggressive exotics such as teasel and poison hemlock. What was once a diverse plant and animal community can become almost a monoculture dominated by exotic weeds providing much less value to wildlife and to people.

Before and After of Bush Honeysuckle

This woodland area suffers greatly from the invasive bush honeysuckle plant.	This section of woodland at Richardson Forest Preserve features thriving native wildflowers. The area was cleared of exotic plants by the Park District's Land Management Department.

When these invasive plants arrived, they didn’t bring with them the natural controls that occur in their homeland. This gives them an advantage over native plants. The same thing can happen in the animal kingdom. Without natural predators and other controls, populations of animals can grow tremendously, as did the Norway rat and the house mouse upon arrival here.

Featured here are four of the more than fifty plants considered to be a problem in local natural areas:

1. Bush honeysuckle (Lonicera maackii): introduced from China primarily as a landscaping plant. In 1960, it was reported as becoming abundant in pastures and wooded areas in Hamilton County, not yet found in any other Ohio county. Today it is our most invasive shrub. Bush honeysuckle leafs out earlier than most native plants, thereby shading out everything under its branches including native wildflowers and young trees. Although the fruits of this shrub are not as nutritious as the fruits of native plants, they are extremely abundant and will be eaten and dispersed by birds. In our area, without any natural predators or controls, bush honeysuckle has become weed enemy number one.
2. Japanese honeysuckle (Lonicera japonica): imported to control erosion and to be used as a landscape plant, this vine quickly forms dense patches climbing over and smothering extensive areas of native vegetation.
3. Creeping Euvonymous (Euvonymus fortunei) an evergreen groundcover, this tough plant carpets the forest floor engulfing everything in its path.
4. Garlic mustard (Alliaria petiolata): introduced in 1868 as a medicinal plant from Europe, this is another prolific pest plant that poses a threat to native flowers and wildlife. By 1991, garlic mustard had invaded 28 northeastern and midwestern states and it now ranges as far west as Kansas. This plant can outcompete native plants and wildflowers by monopolizing light, moisture and nutrients. The animals that depend on the many species of displaced native plants are also eliminated where garlic mustard prevails.

Other non-native invasive plants that escape into natural areas include purple loosestrife (Lythrum salicaria), autumn-olive (Elaeagnus umbellata), glossy buckthorn (Rhamnus frangula), Asian Bittersweet (Celastrus orbiculatus) and burning-bush (Euonymus alatus).

The good news is there are still places not yet invaded by these weeds - places where you can enjoy native wildflowers, insects, trees and birds. The Hamilton County Park District is also working to reclaim prairies, wetlands and forests now dominated by invading weeds. Trained staff and volunteers use techniques and equipment that provide the best results with the least negative impact on the environment. Some of the control methods include cutting, hand pulling, spraying or injecting the safest effective herbicides, mowing and burning. Although we will never control all the invasive plants, the results so far are encouraging. Many acres of parkland have been restored to their natural beauty and diversity.

You can contribute to efforts of encouraging the growth of native wildflowers shrubs and trees by doing the following:

• plant native plants on your property;
• remove invasive plants from your land;
• volunteer with the Park District or other conservation groups;
• ask garden centers to stock native plants;
• avoid purchasing non-native invasives.

With your help, the Hamilton County Park District can continue its legacy of protecting high quality natural areas and providing “Space For All Species”.