Plant Invaders of Mid-Atlantic Natural Areas

Swearingen, J., K. Reshetiloff, B. Slattery, and S. Zwicker. 2002. Plant Invaders of
Mid-Atlantic Natural Areas. National Park Service and U.S. Fish & Wildlife Service, 82 pp.

Introduction

All living things - bacteria, fungi, plants, animals and other organisms - have evolved to live in specific areas on the Earth. Local climate, geology, soils, available water and other natural factors influence which plants and animals live in particular ecosystems and habitats.

Natural areas are wild to semi-wild areas such as fields, forests, streams and wetlands, that are composed of diverse groups of native plants, animals and microorganisms. These biological groupings have evolved over thousands of years into natural communities and ecosystems. Large to small natural areas are all around us and include parks, refuges, preserves, fields, forests, open spaces, undeveloped areas on community and corporate lands, schoolyards, municipal facilities and backyard habitats.

What are native species?
A native species is one that occurs naturally in a particular place without human intervention. Species 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 people 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.

What are invasive plants?
Invasive plants reproduce rapidly, spread over large areas of the landscape and have few, if any, natural controls, such as herbivores and diseases, to keep them in check. Many invasive plants share some important characteristics that allow them to grow out of control. These include: (1) spreading aggressively by runners or rhizomes; (2) producing large numbers of seeds that survive to germinate; and (3) dispersing seeds away from the parent plant through various means such as wind, water, wildlife and people.

How are invasive plants introduced?
People introduce exotic plants to new areas, on purpose and by accident, through a variety of means. Some species are introduced for use in gardening and landscaping, or for erosion control, forage and other purposes. For instance, in the 1930s, the Civilian Conservation Corps planted kudzu vine (introduced from Japan), throughout the Southeast to help stabilize soil in erodible areas. Kudzu grew so prolifically that it was nicknamed the "vine that ate the South." Others come in unknowingly, on various imported products or in soil, water and other materials used for ship ballast. Many invasive aquatic plants are introduced by dumping unwanted aquarium plants into waterways. Once established in a new environment, some exotic species proliferate and expand over large areas, becoming invasive pests.

How do invasive plants spread?
Invasive plants spread by seed, vegetative growth (producing new plants from rhizomes, shoots, tubers etc.) or both. Seeds, roots and other plant fragments are often dispersed by wind, water and wildlife. Animals spread invasive plants by consuming fruits and depositing seeds as well as transporting seeds on their feet and fur. People also help spread invasive plants by carrying seeds and other plant parts on shoes, clothing and equipment and using contaminated fill dirt and mulch. Invasive aquatic plants are often spread when plant parts attach to boat anchors and propellers.

Why are invasive plants a problem in natural areas?
Like an invading army, invasive plants are taking over and degrading natural ecosystems. Invasive plants disrupt the intricate web of life for plants, animals and microorganisms and compete for limited natural resources. Invasive plants impact nature in many ways including growing and spreading rapidly over large areas, displacing native plants, including some very rare species, reducing food and shelter for native wildlife, eliminating host plants of native insects and competing for native plant pollinators. Some invasives spread so rapidly that they muscle out most other plants, changing a forest, meadow, or wetland into a landscape dominated by one species. Such "monocultures" (stands of a single plant species) have little ecological value and greatly reduce the natural biological diversity of an area.

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. 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.

How to prevent spread of invasive plants
Become familiar with invasive plant species in your area. When selecting plants for landscaping, avoid using known invasive species and those exotic species exhibiting invasive qualities. A few common ornamental plants that show invasive tendencies and that have become problematic elsewhere in the U.S. include: pampas grass (Cortaderia selloana); jubata grass (Cortaderia jubata); fountaingrass (Pennisetum setaceum); Chinese fountaingrass (Pennisetum alopecuroides); star-of-Bethlehem (Ornithogalum umbellatum); creeping lilyturf (Liriope spicatum) and water hyacinth (Eichhornia crassipes). Ask for native plant alternatives at your nursery. Obtain a list of plants native to your state from your native plant society, state natural resources agency, or the U.S. Fish and Wildlife Service, Chesapeake Bay Field Office (see references). Carry this list with you to nurseries to help with plant selection.

If you already have invasives planted on your property, consider removing them and replacing them with native species, such as those suggested in this guide. Refer to reputable resources (see references) for more information on identifying invasive plants and the best ways to control or remove a specific plant. When visiting a natural area, be alert for invasive species. If you see some, notify the agency or organization responsible for managing the land. Before you leave, avoid carrying "hitchhiking" plant material by taking time to brush seeds from clothing and shoes and remove plant material from boats, trailers and other items.

Information about this guide
This illustrated handbook describes a variety of highly invasive plants impacting the region's natural areas. It provides identification tips, a few suggested native plant alternatives and some control information for a variety of invasive aquatic and terrestrial species in the mid-Atlantic region.

For purposes of this manual, the mid-Atlantic region includes the District of Columbia and the states of Delaware, Maryland, New Jersey, Pennsylvania, Virginia and West Virginia. More than 200 exotic plant species have been identified by natural resource managers as problematic invaders of natural areas in the mid-Atlantic region. The plants included in this guide are some of the most problematic invasives that are responsible for significant degradation of natural communities in this region. This guide is not intended to be a complete resource on invasive plants in the mid-Atlantic region and a list of organizations is provided where readers can obtain additional information. Plants excluded from this guide should not be assumed to be environmentally safe.

For more complete information on invasive plants, including species not covered in this guide, contact the Mid-Atlantic Exotic Pest Plant Council at http://www.ma-eppc.org or the Plant Conservation Alliance, Alien Plant Working Group at http://www.nps.gov/plants/alien/.

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