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Harmful to livestock – not just horses and cattle – goatsrue is a threat to all of Oregon. Brought into Utah in the late 1800s, goatsrue is now found in several other states. Fortunately, goatsrue is still only found in a handful of places in Oregon, almost all in the Portland metro area.

Gorse infestations are mainly found in Oregon’s southwestern coastal counties. No patches are known in Portland yet, but small patches have been found in the counties around Portland.

Goutweed is a species of concern known for filling in garden spaces and for being very hard to control. Its sale is prohibited in several New England states and has been noted as invasive throughout the East Coast, Midwest, and Pacific Northwest.

Italian arum, a British native, is another commonly swapped species with a reputation for being extremely difficult to remove.

Italian thistle or slender flowered thistle is on the Required Eradication List. All sightings should be reported. Learn more about how to report this plant.

Jubata grass is on the Required Eradication List. All sightings should be reported. Learn more about how to report this plant.

Knotweed, sometimes known as Japanese bamboo, has earned a reputation for creating extensive ecological damage as well as for wreaking havoc on private property in the Pacific Northwest.

Kudzu is a fast-growing vine that climbs trees, powerlines, and structures. Kudzu vines will smother a tree—keeping the tree from getting light or causing it break from the weight of the vines. Kudzu is extremely rare in the Portland area. No new plants have been seen since the early 2000s.

Be cautious of lesser celandine at plant swaps or when sharing plants with friends and neighbors. It was once sold as an ornamental plant and has become common throughout Portland. Lesser celandine is known for blanketing yards and natural areas.

Formerly listed as yellow hawkweed, meadow hawkweed is on the Required Eradication List. All sightings should be reported. Learn more about how to report this plant.

Milk thistle poses a health risk for grazing animals making it a dangerous invasive for Oregon. Grown for the herbal supplement market, milk thistle has escaped cultivation. Locally, it has been found along the Columbia Slough in Portland, throughout Sauvie Island, and in Clark County, Washington.

For a time, orange hawkweed was being spread in wildflower seed mixes. Always be suspicious of unlabeled wildflower seed mixes. Better yet: Don’t use them at all. Found in Multnomah and Clackamas counties and throughout North Oregon Cascades passes, orange hawkweed threatens to spread farther.

Paterson's curse is poisonous to grazing animals. Although it likes hot, dry weather, it has been seen in Portland. It may have come to Oregon packaged in a wildflower seed mix. Always check all wildflower seed packets to be sure they don’t contain this or other invasive plants.

Pokeweed is a shrub native to the southeastern United States. It is considered edible when properly prepared but toxic to the unwary. The roots are thought to be the most toxic part of the plant, but sickness can result from eating other parts as well.

Policeman’s helmet is widespread and causing problems along the Oregon coast and in the Coast Range. Although not common in Portland, it is known to be in a few places and must be managed to prevent further spread.

Purple loosestrife is an invasive plant with small, magenta flowers. While pretty, it takes over and is a particular problem in sensitive areas like wetlands, which protect water quality and provide critical habitat for many animals. Purple loosestrife threatens the delicate balance in wetlands.

Although not currently known to be in Portland, Russian knapweed is a Required Eradication species. Infestations cause big problems for Oregon's farmers and ranchers. Growing in dense clumps, Russian knapweed forces out crops or native plants and is inedible to livestock and wildlife.

Saltcedar is on the Required Eradication List. All sightings should be reported. Learn more about how to report this plant.

Scotch thistle causes problems mostly in rangeland and pine woodlands. Thistle thickets take the place of plants that large animals, like cattle and elk, eat. The plant costs a lot to remove, and treatment must be repeated for several years. Scotch thistle has been found in Clackamas County.

Spurge laurel, a broadleaf shrub, was introduced as an ornamental plant to the Pacific Northwest and now is invasive. The berries, leaves, and bark are poisonous if eaten. The sap can cause rashes and swelling, and the fumes can make it hard to breathe. Be prepared if you handle this plant.