The Oregon Invasive Species Council's website states that invasive species are the most significant threat to native plants and animals other than the loss of habitat. Oregon is home to several invasive plant species that have the ability to adversely affect the state's native plants. These invasive species are both terrestrial and aquatic, introduced to the state by accident or as an ornamental species that then got out of control.
Kudzu (Pueraria lobata) is a climbing type of vine that can engulf shrubs, trees and structures. Kudzu comes from Japan and came to America in 1876 as a gift from the Japanese to become an ornamental species. Kudzu features 6 to 8 inch long leaves and hanging clusters of flowers, and produces a smell similar to grapes. The fruits are in the form of flat brown pods and the stems of kudzu can be as wide as 4 inches. Kudzu can produce up to 30 separate vines from one root crown and the taproot of this invasive plant is very large, as long as 6 feet. Kudzu can destroy native plants by covering them with a mantle of leaves, or by damaging the host plant with its sheer weight. Kudzu grows as much as 1 foot per day and thrives under many different growing conditions. Kudzu typically exists along the edges of forests, along the side of the road and in other spots where sunlight can easily reach it. Although kudzu did not appear in the western part of the United States until 2000, it now exists in Oregon's northwest corner.
Yellow Floating Heart
Yellow floating heart (Nymphoides peltata) is an aquatic invasive species in Oregon that roots itself on the bottom of water as deep as 13 feet. The heart-shaped leaves are up to 4 inches long and have a purple underside. The leaves attach to lengthy stalks that develop from the rhizome root system that spreads underwater. The plant produces yellow flowers with five petals. Yellow floating heart grows dense clumps and prevents any light from filtering through the water to native plants. These areas of thick vegetation in turn create stagnant water with lowered levels of oxygen. Fishing, water-skiing, swimming and boating become problematic when yellow floating heart clogs waterways. Yellow floating heart, introduced to be an ornamental species from its native Mediterranean origins, exists in Oregon in Lane and Washington Counties, located in the northwestern section of the state.
Matgrass (Nardus stricta ) grows slowly, but is long-lived. A type of grass that produces bristly, hard leaves, matgrass comes from eastern portions of Europe. The species first showed up in Oregon around 1962. Matgrass has tight roots and is difficult to pull up. Matgrass is blue-green in color and comes back year after year. Matgrass often grows near waterways and in meadows and fields that receive plenty of rain. Grazing animals do not find matgrass tasty, and will pass it over in favor of other native grasses. This allows matgrass to expand its territory wherever this occurs. Matgrass is tough to find because it blends in with native grasses, making it a difficult plant to eradicate. Matgrass in Oregon is a problem in Klamath County in the south/central part of the state.