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Invasive Plant: Kudzu
Information
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.
On this page
At a Glance
Scientific name: Pueraria lobata
Annual, perennial, or biennial? Perennial
Conditions it likes best: Kudzu likes a lot of sun, but it can grow with less light and in many different kinds of soil.
How it spreads: Kudzu spreads by runners or stems that creep along the ground and sprout wherever a leaf node (intersection) stays in contact with soil.
How it causes damage: Kudzu vines climb and smother other vegetation, which makes it particularly dangerous to trees and forests.
Best time and way to manage: Although not seen in Portland recently, Multnomah and Clackamas counties have had patches of kudzu in the past. It is one of the state’s priority species and requires professional management.
Report patches of this plant? Yes. Oregon law requires that you report all sightings immediately for assistance. Use the online tool at Oregon Invasives Hotline or call 866-INVADER to let the state know when and where you found this plant. You may also contact Portland’s Environmental Services (contact information on this page), who will notify the state of Oregon for you and help you remove these plants. A photo and a location are required.
How to Identify Kudzu
Kudzu blooms in mid-summer with large, hanging clusters of red or purple sweet-smelling blossoms. Photos by Tom Forney, Oregon Department of Agriculture
Winter–Spring. Kudzu loses its leaves every winter. Plants grow leaves back in the spring (May or June). In places like Georgia and North Carolina, kudzu can grow up to 1 foot per day and have vines 1 to 4 inches thick. In Oregon and Washington, kudzu is probably less aggressive. Young stems are covered with stiff reddish brown hairs but become woody and smooth when fully grown. Roots are fleshy with taproots up to 12 feet deep. Leaves have 3 leaflets, which are nearly heart-shaped.
Summer–Fall. Kudzu blooms mid-summer through early fall with large, hanging clusters of red to purple sweet-smelling blossoms. These upright, pea-like flowers are 4 to 8 inches long with a grape-like smell. Seeds form in dark-brown flat, hairy pods in the fall.
How and When to Remove Kudzu
The kudzu leaf has three leaflets. Report all sightings of kudzu.Requires professional management. Kudzu is a high priority plant and would be managed by professionals from the City or the State. This plant is on Oregon’s and Portland’s required eradication list, so it is important to report any plants found so they can be removed.
Check. Check the site for new plants at least once a year and especially for the first 2-3 years after removal.
Replant. After a year or two of managing this plant, consider planting native or less aggressive non-native plants. There are now many groups who can suggest new plants.
Prevention is Best Practice
Clean your boots, pets, and maybe even your tires when you finish a hike or trail ride in Pacific Northwest natural areas, or if you have invasive plants on your own property. Cleaning boots and pets keeps invasive plants from spreading to new places. Be careful when trading plants with neighbors and fellow gardeners to make sure you’re not trading this or any other plant of concern.
Be Aware of Look-alikes
Travelers’ joy (Clematis vitalba), which has leaves with 5-7 oval leaflets (parts) and fluffy seeds, is often reported as kudzu. Kudzu leaves have only three triangular leaflets.
Properly Dispose of Invasive Plants
To prevent spreading invasive plants:
Never place plants or seeds in your compost or yard debris.
Never throw pulled plants on the ground or into the street or sidewalk.
Put all pulled plants, bulbs, or seeds into a plastic bag and put the bag in the trash.
