Although invasive plants are almost always not native to a region, it is important to note that most nonnative species are not invasive. In addition, some native species can become invasive. The following definitions are used by the Chicago Botanic Garden:
What Makes a Plant Invasive?
When plants are introduced to a new location, either intentionally or accidentally, they can spread prolifically, outcompete native species for resources, and eventually dominate the landscape. Biologists are studying the mechanisms underlying a taxon’s ability to become invasive, but for now it is still difficult to predict whether or not a species will become invasive in a new habitat. Some factors common to many invasive plants include the following:
People have introduced the vast majority of invasive species, either accidentally or deliberately. For example, kudzu was introduced to control soil erosion. Many nonnative species came to the United States with the colonists, who wanted familiar food and garden plants. Some invasive species were, or still are, popular ornamental plants used in landscaping. The rapid expansion of global trade and human mobility has led to many species arriving accidentally. Seeds can hitch rides to new locations in cargo or even stuck to the bottom of hiking boots.