Center for Urban Restoration Ecology, School of Environmental & Biological Sciences
Rutgers, The State University of New Jersey
Brooke Maslo, Ph.D
Across all regions of the world, every ecosystem has formed over millions of years and has its own unique character. Through a series of both competitive and symbiotic interactions, each native species plays a role in the persistence of its ecosystem. For example, insects have developed specialist relationships with the plants of their region, either promoting the reproduction of a plant species through pollination or by holding a species’ population in check through herbivory. Birds, in turn, moderate the insect populations so that no species can completely extirpate another. Birds also disperse plants by carrying their nutritious fruits far and wide, dropping seeds in new areas. These complex relationships have formed over time, with each species carving out a niche for itself and contributing to a rich, diverse, and productive ecosystem.
However, over the last 400 years, both plant and animal species have been transported by humans across the oceans and have settled in new habitats. Some species were transported deliberately, for horticultural purposes or simply to remind settlers of their old countries.
Other species, especially insects and microorganisms, were carried accidentally, as stowaways in cargo containers or in ship ballasts. Although some of these species did not reproduce successfully in their new regions, some have experienced population explosions.
Today, one of the biggest ecological threats to native habitats is the continued introduction and spread of invasive plant species. Invasive plant species have a competitive advantage over native species because they are freed of the insects, birds, and animals that eat them, and the resident wildlife in their new habitat has not evolved a way of overcoming the invasive plant’s physical or chemical defenses. Therefore, their populations can grow unchecked in new habitats. Some species “leaf out” earlier and stay greener longer, creating and storing more energy. Therefore, these invasive plants can grow faster and produce more seeds than native plants. Because of these properties, invasive plants crowd out or strangle natives and often form dense monocultures over large areas. This loss of biodiversity leads to decreased habitat value for native wildlife (reduced food and shelter, depleted soil nutrients, clogged waterways, and increased erosion. Overall, invasive plants cause an estimated $120 billion of environmental damage every year.
Tragically, our extensive knowledge of the damage caused by invasive species has not yet halted their sale in nurseries across the country. Unfortunately, the reasons these plants are invasive are the same reasons they are so popular in horticultural markets. They grow quickly, are deer and insect resistant, and they stay green for long periods of time. The problem is that the seeds these plants produce are carried into and destroy our natural lands.
The following pages provide information on some common invasive plants of the Northeast and mid-Atlantic regions, including identification, control measures, and native alternatives for your landscape. The more we do to increase the habitat value of our yards, the more we support our natural areas in overcoming plant invasion and persisting, with their valuable ecological services for us.
Invasive Plants for Sale
To assist in the fight against invasive plants, avoid purchasing the following plants from nurseries and garden centers. If you have these plants in your yard already, consider replacing them (either all at once or as existing plants die) with the suggested native alternatives.
Other Plants That May Be Creeping In...
The following group of plants has invaded both natural and human-modified landscapes. By eradicating these species from your property, you will increase its wildlife habitat value while reducing the seed sources available to colonize natural lands. Replacing invasive stands of plants with native plant material will help buffer your property against further invasion, but always be on the lookout.
Unfortunately, the above-listed species are only a small percentage of the total number of invasive plants that are threatening our ecosystems. But if we are conscious of what we plant in our yards, and if we take action against plant invaders that opportunistically colonize our property, we can make significant headway in the fight to save our native habitats. Table 1 provides a list of references for more information on the identification and control of invasive plants., and Table 2 lists some native plant nurseries in the mid-Atlantic region.