Question: I keep seeing these plants that look kind of like sweet peas with purple flowers along fence lines. They are all over the place. Are they native?
Answer: While there are pea plants native to the Pacific Northwest, the one you are describing is not one of them. The vigorous, purple-flowered plant (or occasionally white) you are seeing is everlasting peavine (Lathyrus latifolius), a native of Europe that is now widely naturalized in the Willamette Valley and beyond. Unfortunately, it is classified as a noxious weed by the Oregon Department of Agriculture.
As the “peas” are toxic to humans, it was introduced originally as a component of wildflower mixes and for erosion control.
This is an herbaceous perennial vine whose stems can grow up to 7 feet long. Along fences, it can form dense growth, and it will grow up into trees and shrubs.
It is particularly toxic to humans and certain livestock such as horses. The seeds do provide a food source for some native birds, but it is an increasing problem as it crowds out native vegetation.
Individual stands can be controlled with repeated cutting before seed set.
The Master Gardeners’ Question of the Week is courtesy of Oregon State University Extension Service’s Master Gardeners. The Master Gardeners are trained volunteers who offer homeowners help with gardening problems. Call 503-373-3770 in Marion County or 503-623-8395 in Polk County to talk with a Master Gardener.