The Silent Invasion

By Kathy Reshetiloff

We've been invaded, but there are no armies, no soldiers. This is a silent invasion. The aggressors are invasive plants that are silently creeping over vast expanses of natural areas, wreaking havoc on local ecosystems.

The majority of these invasive plants are also non-native. Plants native to North America are generally recognized as those occurring on the continent prior to European settlement. Non-native plants are species that have been introduced to an area by humans from other continents, states, ecosystems and habitats. Many non-native plants have great economic value for agriculture, forestry, horticulture and other industries and pose little to no threat to our natural ecosystems. Others have become invasive and pose a serious ecological threat.

Plants are considered invasive if they spread out of control dominating the local environment and crowding out native plants. Because they have been introduced into an environment in which they did not evolve, there are no natural predators, parasites or other controls to keep these invasive plants in check. Invasive plants grow fast and mature early in the season and reproduce profusely. Some invasive vines will actually bring down trees by their sheer weight.

They out-compete native plants for light, water and nutrients and eliminate entire native plant communities---and they change the composition of the landscape. The ecological balance of plants, animals, soil, and water achieved over many thousands of years is destroyed. As native plants are displaced, animal populations that rely on the plants for food and shelter also decline. When invasive plants take over wetlands, forests or meadows, we lose the native plants and the habitats that local wildlife need.

In the United States, invasive plants already infest more than 100 million acres and continue to increase by 8 to 20 percent annually. Once established, invasive plants require enormous amounts of time, labor and money to control or eliminate. Invasive species cost the United States an estimated $34.7 billion each year in control efforts and agricultural losses.

Invasive plants also affect the type of recreational activities that we can enjoy in natural areas such as boating, bird watching, fishing and exploring. Some invasives become so thick that it is impossible to access waterways, forests and other areas.

Estimates indicate that non-native plants infest 4,600 new acres of federal land each day. Each year, non-natives spread into an area larger than the state of Delaware. Overall, invasive plants threaten every aspect of the North American environment including national wildlife refuges, national parks, recreation areas, wilderness areas, forests, wetlands and croplands.

Spring has sprung and, like countless other Americans, you're going to spend some time and money sprucing up and landscaping your yard. Be careful when choosing plants---you could unknowingly introduce an invasive plant. Many times homeowners don't know that a plant in their yard can become a menace in the wild. However, some common landscape plants found at most nurseries are invasive.

Become familiar with invasive plant species in your area and avoid planting them. Ask for native-plant alternatives at your nursery. If you already have invasive plants on your property, consider removing them and replacing them with native species. Here are a few troublesome plants to avoid, followed by suggested native alternatives:

Purple loosestrife (Lythrum salicaria); native alternatives: blazing star (Liatris spicata), cardinal flower (Lobelia cardinalis), obedient plant (Physostegia virginiana).

Chinese wisteria (Wisteria sinensis) and Japanese wisteria (Wisteria floribunda); native alternatives: American wisteria (Wisteria fructescens), trumpet creeper (Campsis radicans) trumpet honeysuckle (Lonicera sempervirens).

Bradford pear (Pyrus calleryana 'Bradford'); native alternatives: redbud (Cercis canadensis), serviceberry (Amelanchier canadensis), southern arrowwood (Viburnum dentatum).

The National Park Service and U.S. Fish and Wildlife Service have put together the publication entitled "Plant Invaders of Mid-Atlantic Natural Areas." The color guide describes common invasive plants and alternative native plants to use instead. To receive a copy, contact U.S. Fish and Wildlife Service, Chesapeake Bay Field Office at (410) 573-4500 or download a copy from www.nps.gov/plants/alien/pubs/midatlantic.

For more information, visit the USFWS, Chesapeake Bay Field Office's BayScapes website at www.fws.gov/r5cbfo/Bayscapes.htm.