Invasive Non-Native Plants vs. Native Plants

Source: StewardshipGarden.org, Environmental Protection Agency

What is a Native Plant?

Native plants (also called indigenous plants) are plants that have evolved over thousands of years in a particular region. They have adapted to the geography, hydrology, and climate of that region. Native plants occur in communities, that is, they have evolved together with other plants. As a result, a community of native plants provides habitat for a variety of native wildlife species such as songbirds and butterflies.

What is a non-native species?

Every organism has a home, a particular region where it has existed for thousands of years and evolved in association with specific environmental conditions and with the specific plants and animals including parasites and disease causing organisms. "Native" species occur in their natural regions without the direct or indirect activities of humans. A "non-native" species occurs outside that natural range. In North America, many non-native plants were brought over for agriculture, medicinal, and ornamental purposes. Many plants were introduced accidentally as well. The introduction of the non-native organisms continues to be a problem today due to our increased travel and international trade. Not all non-native plants or animals become a problem. Many non-native plants represent significant human food sources. However, some of these plants have certain aggressive traits that make them an invasive species.

What is an invasive species?

Invasive species are those non-native species that can significantly disrupt natural communities causing environmental or economic harm. In a new environment, invasive plants are released from the natural constraints of their native ranges. They lack the control of herbivores, parasites, diseases, and competition that was present in their native habitats. Invasive plants exhibit both rapid growth and reproduction rates because of abundant seed production, reproduction through vegetative clones, and/or extended growing seasons.

Why are invasive non-native plants a concern?

Invasive, non-native plants displace native plants and animals, and so disrupt ecological processes, and degrade biological resources. Invasive plants often lack the natural population controls that keep them in check in their native ecosystems. Controls existing in the new ecosystem (herbivores, parasites, diseases and native plants) are not adapted to make use of the non native invaders. This disparity of population controls, in addition to their rapid growth and reproduction, creates a situation in which the invasive plants are better competitors. They reduce the amount of sunlight, water, nutrients, and space available to native plants, eventually competing with and replacing natives. This represents a loss in habitat and food source for wildlife. Invasive plants have even shown to alter hydrological patterns and soil chemistry. In the big picture, invasive plants reduce biodiversity.

How do invasive, non-native plants get into natural areas?

Our increasing global society has transported plants worldwide at an unnaturally fast pace. Once a new species is introduced, either from another continent, or another region of North America, it seeds may be carried by wind, water, animals or vehicles. Seeds or vegetative structures can be deposited miles from their original sites, allowing the species to spread at a rate that it could never accomplish on its own. Unsuspecting homeowners may use invasive, non-native plants in their landscaping. Species may easily spread into natural areas from nearby yards and lawns.

Why use Native Plants?

Native plants do not require fertilizers. Vast amounts of fertilizers are applied to lawns. Excess phosphorus and nitrogen (the main components of fertilizers) run off into lakes and rivers causing excess algae growth. This depletes oxygen in our waters, harms aquatic life and interferes with recreational uses.

Native plants require fewer pesticides than lawns. Nationally, over 70 million pounds of pesticides are applied to lawns each year. Pesticides run off lawns and can contaminate rivers and lakes. People and pets in contact with chemically treated lawns can be exposed to pesticides.

Native plants require less water than lawns. The modern lawn requires significant amounts of water to thrive. In urban areas, lawn irrigation uses as much as 30% of the water consumption on the East Coast and up to 60% on the West Coast. The deep root systems of many native Midwestern plants increase the soil's capacity to store water. Native plants can significantly reduce water runoff and, consequently, flooding.

Native plants help reduce air pollution. Natural landscapes do not require mowing. Lawns, however, must be mowed regularly. Gas powered garden tools emit 5% of the nation's air pollution. Forty million lawnmowers consume 200 million gallons of gasoline per year. One gas-powered lawnmower emits 11 times the air pollution of a new car for each hour of operation. Excessive carbon from the burning of fossil fuels contributes to global warming. Native plants sequester, or remove, carbon from the air.

Native plants provide shelter and food for wildlife. Native plants attract a variety of birds, butterflies, and other wildlife by providing diverse habitats and food sources. Closely mowed lawns are of little use to most wildlife.

Native plants promote biodiversity and stewardship of our natural heritage. In the U.S., approximately 20 million acres of lawn are cultivated, covering more land than any single crop. Native plants are a part of our natural heritage. Natural landscaping is an opportunity to reestablish diverse native plants, thereby inviting the birds and butterflies back home.

Native plants save money. A study by Applied Ecological Services (Brodhead, WI) of larger properties estimates that over a 20 year period, the cumulative cost of maintaining a prairie or a wetland totals $3,000 per acre versus $20,000 per acre for non-native turf grasses.