Invasive Species
Plants that grow aggressively and outcompete other species are called invasive species. Invasive plants are usually those that were introduced, either intentionally or unintentionally, into a locality where they previously did not grow. Introduced plants, also called exotics or alien species, form an important part of our environment, contributing immensely to agriculture, horticulture, landscaping, and soil stabilization. But among the thousands of plant species introduced to North America, approximately 10 percent display the aggressive growth tendencies of invasive species. Although the terms exotic, alien, and invasive are sometimes used interchangeably, not all exotic plants are invasive. In addition, some native species, those plants that grew in an area prior to European settlement, can be invasive, especially as natural landscapes are altered.
Characteristics of Invasive Species
Invasive species are not a separate biological category, and all types of plants, including vines, trees, shrubs, ferns, and herbs, are represented by invasive species. They do, however, share certain characteristics that help them rapidly grow and invade new areas. Invasive plants typically exhibit at least some of the following:
- production of many seeds
- highly successful seed dispersal
- no special seed germination requirements
- grow in disturbed ground
- high photosynthetic rates
- thrive in high-nutrient conditions
- rapid growth and maturity
- early maturation
- reproduction by both seeds and vegetative means
- long flowering and fruiting periods
Most exotic plants do not pose an obvious threat to native plants when they are first introduced, but we do not fully understand the dynamics of what makes plants invasive.
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