List of Invasive Plants in Oregon

Invasive plants are plants that have been introduced from their native area, and because they are non-native, the plants have few natural limits and tend to spread rapidly. Although some invasive plants are ornamental, the plants can become a serious problem and a threat to Oregon's natural environment as they destroy riparian areas, choke out native plants and drain water and nutrients needed for agricultural crops and livestock.

Scotch Broom

Scotch broom (Cytisus scoparius), is an perennial evergreen shrub that will be covered with small yellow flowers from April to June. Scotch broom is a prolific grower that will readily invade coastal sand dunes and other recreational areas, in addition to both public and private lands and forests. Scotch broom costs Oregon millions of dollars in maintenance costs and lost timber revenues every years.

Butterfly Bush

Butterfly Bush (Buddleja davidii), is a perennial shrub that can grow to heights of up to 10 feet. Although the plant blooms in mid to late summer with small, purple blooms that resemble lilacs, butterfly bush is an invasive plant that can soon grow out of control. Butterfly bush threatens open areas such as meadows and slopes, as well as dunes, riparian areas and reforested sites, where it rapidly chokes out native plants.

Blessed Milkthistle

Although blessed milkthistle (Silybum marianum) is a member of the sunflower family, it's not nearly as welcome as the friendly, yellow blooms that we're familiar with. The pricky leaves of blessed milk thistle grow to lengths up to 1 foot long. The stems can grow to be 6 feet tall, topped with bristly purple or red flowers. Blessed milk thistle is native to Europe, and is believed to have been introduced to Oregon in cattle feed.

Yellow Floating Heart

Yellow floating heart (Nymphoides peltata), is an aquatic perennial plant and a serious threat to Oregon's ecosystem. Yellow floating heart grows in ponds, lakes and slow-moving rivers, in water depths of 2 to 13 feet. Also known as marshwort or fringed water lily, yellow floating heart grows from underwater rhizomes that send up long stems topped with heart-shaped leaves and bright yellow blooms that float on the surface of the water. The plants form patches so dense that it can even displace native plants and animals.

Old Man's Beard

Old man's beard (Clematis vitalba), is a woody vine that will produce small, greenish-white flowers all summer. The deciduous vines can grow up to 30 feet in length, choking out native trees and shrubs. Once the tree or shrub is dead, old man's beard will continue to grow on the ground in layers so thick that any hope of regrowth of native plants is eliminated. As a result, food sources for birds, insects, lizards and wildlife are choked out. Old man's beard grows prolifically along river banks, roadsides, forest edges, or any area that isn't grazed or managed.

Keywords: Scotch Broom, Yellow Floating Heart, Butterfly Bush, Invasive Plants in Oregon

About this Author

M.H. Dyer is a long-time writer, editor and proofreader. She has been a contributor to the East-Oregonian Newspaper and See Jane Run magazine, and is author of a memoir, “The Tumbleweed Chronicles, a Sideways Look at Life." She holds an Master of Fine Arts from National University, San Diego.