Most plant species have predators in their natural range that keep their population numbers balanced, but when a foreign plant is introduced to a new environment, it may lack those predators and outnumber other plants that are sources of food for birds, reptiles, and insects. This can result in the decline of wildlife in a given area, or the complete extinction of a species.
The major problem with invasive plants is that many people don't know they exist, and have continued to plant or purchase them throughout the years.
Take for instance Japanese barberry, a spiny shrub that grows 2 to 8 feet, with pale yellow flowers and bright red berries.
It was first introduced to the United States through Russia in 1875 and first planted in New York City's Botanical Garden and by settlers for hedgerows, dye and jam. However, in recent years, the plant, commonly found in people's gardens for decorative purposes, has rapidly spread from people's backyards into the wild rapidly. It forms dense stands in forests, woodlands, pastures and meadows, and alters soil pH, nitrogen levels, and biological activity in the soil.
Since there is currently no law in the state against selling invasive plants at nurseries, Japanese barberry is commonly purchased by landscapers and homeowners.
Sandy Brousseau, a greenhouse expert at Olsen's Hardware and Gardening Center on New Scotland Road has been selling Japanese barberry for several years.
"A lot of times they end up taking over a habitat for our natives and become real pests," she said.
Brousseau said she informs customers about the dangers of the plant, and supports a law against selling them.
"Somebody would have to do a plant-by-plant assessment, and some states should, because it's not something you want being totally out of control," she said.
Besides Japanese barberry, there are also several other invasive plants that crowd natural areas in the Capital District. The most prominent are purple loosestrife, spotted knapweed, multi-flora rose, common buckthorn, exotic bush honeysuckle and garlic mustard.