Native plants are plants that were not introduced by humans, and by definition they can’t be invasive. Only a small percentage of non-native plants are invasive, but those that are can cause a great deal of damage.
Invasive plants have the following characteristics:
» They grow rapidly.
» They adapt easily to different habitats.
» They mature early.
» They produce large amounts of seed.
Invasive plants can, therefore, easily escape cultivation and find their way into natural areas. In addition, they have no natural enemies, such as insects, to keep them under control. These traits enable invasive plants to out-compete native plants for light, water and space, and fewer native plants means decreased habitats for native birds and other animals. Some invasives bring other problems as well.
Question: How can I tell if I have invasive species in my garden?
Answer: You may very well have them, because the state Department of Land and Natural Resources’ Division of Forestry and Wildlife reports that approximately 70 percent of the state’s introduced invasive plants were brought in for ornamental uses.
One of the worst invasive plants here is miconia. It was introduced on Oahu in the 1960s and on Maui in the ’70s as a garden plant and can now also be found on Hawaii island and Kauai. When a miconia plant reaches maturity, at about four years, it can produce about 3 million seeds — several times a year! — that are easily spread by birds. Miconia can shade out native plants and increase erosion.
Other garden plants that are considered invasive in Hawaii include the Australian tree fern, pampas grass, New Zealand flax, lantana and fountain grass. Fountain grass not only increases the incidence of fires, it can survive fire, whereas native plants can’t.
Q: What should I do about invasive species?
A: Gardeners can be part of the solution by not planting invasives. Preventing their introduction is the easiest way to manage these plants, because they’re very good at spreading and thriving once they’re here.
To find out if something is invasive and what to plant instead, gardeners can contact their local extension office.
The University of Hawaii at Manoa’s College of Tropical Agriculture and Human Resources has several publications on invasive species and their alternatives, as well other gardening information, at www.ctahr.hawaii.edu/Site/Info.aspx. You can also check out the Hawaii Pacific Weed Risk Assessment website at https://sites.google.com/site/weedriskassessment/home, where you can ask to have a specific plant assessed for invasive potential if it hasn’t already been categorized.
Lorraine Brooks is an urban horticulture extension agent and the Maui Master Gardener coordinator with the University of Hawaii’s Cooperative Extension Service, part of the College of Tropical Agriculture and Human Resources. Email her at llb@hawaii.edu. To contact your local UH Master Gardener Program, visit www.ctahr.hawaii.edu/UHMG.
