BackPage Primer from Environmental Building News
Invasive Plants
Native or indigenous plants are those that have been present historically in a region and were not introduced from “elsewhere”—though what defines “elsewhere” is debated. When we move plant species from their native region into a foreign ecosystem, those plants often lack native controls (predators), so may take on invasive characteristics: out-competing and eliminating native species and disrupting habitat for native flora and fauna that depend on a varied, balanced ecosystem for their survival.
Kudzu vine, garlic mustard, crown vetch, and Japanese honeysuckle are just a few examples of well-known invasive species that have radically changed the balance of ecosystems in many regions of the U.S. Even selecting a “sterile” cultivar of an otherwise invasive plant can be dangerous: several varieties of the notoriously invasive purple loosestrife sold as “sterile” actually produce fertile seeds, pollen, or both.
Invasive plants are especially opportunistic when ecosystems are disturbed—construction sites are a prime example—so it’s important to be proactive about establishing native plants quickly to prevent invasives from filling the void.
Just as certain native species can become invasive in a disrupted ecosystem (blackberries in the Northwest, for example, and poison ivy in the East), not all nonnative plants will behave invasively—some species, including some ornamentals, may be perfectly safe to plant outside their native habitats. Sedums and other plants typically used on green roofs are examples of these.
When making landscaping choices, be aware that nonnative species, whether invasive or not, have often evolved in other climates that have different levels of precipitation, sunlight, soil nutrients, and other resources, as well as different blights and predators. You’ll have to provide what your climate can’t, and this can become expensive, time-consuming, and environmentally damaging when you factor in water use, chemical herbicides, pesticides, and fertilizers as well as pollution from landscaping equipment. Uniform turf grass, for example, is responsible for some 30% of municipal potable water use in the eastern U.S. and closer to 60% in the West, not to mention huge amounts of chemical inputs, labor, fossil fuel use from lawn equipment, and other maintenance needs.
Selecting native species helps ensure that you will have a landscape that not only looks healthy without excess irrigation and inputs but also is healthy for humans, wildlife, and the planet. The goal of a natural, native landscape should be a balanced ecosystem.
For information on invasive species in your area, consult with a landscape architect, contact a regional environmental center, or visit the National Invasive Species Information Center at
www.invasivespeciesinfo.gov.
July 1, 2010
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