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Oriental clematis is a deciduous vine or scrambling shrub with yellow flowers that originates from central Europe and Asia. Identification can be tricky because of the many cultivars of this and similar Clematis species that have been sold in the nursery trade, sometimes under the same names. Oriental clematis has escaped cultivation and naturalized in Washington, Oregon, Colorado, Idaho, New Mexico, Nevada, and Utah. In Washington, this plant is mostly limited to a few large infestations near and along the Yakima River, although it may be present in gardens as well.
Legal status in King County, Washington
Oriental clematis is a Class A Noxious Weed in Washington State due to its limited distribution in the state and the potential for significant impact to state resources. Public and private landowners are required to control this plant when it occurs on their land.
This species is also on the Washington quarantine list (known as the prohibited plants list) and it is prohibited to transport, buy, sell, offer for sale, or to distribute plants or plant parts, seeds in packets, blends or "wildflower mixes" of this species, into or within the state of Washington.
Because of the difficulty in distinguishing this oriental clematis from other clematis species, we recommend contacting the noxious weed program for a positive identification before removing. There are currently no records of this plant escaping cultivation in King County, so if you do find oriental clematis in King County, please report the location right away.
Identification (see below for more photos)
Deciduous vine that grows as a climber or scrambling shrub that attaches itself by way of tendril-like stems
Flowers have four yellow to greenish-yellow sepals (look like petals) and are about one inch long
Yellow sepals (look like petals) spread outward and tend to curve back at the tips as flowers mature
Flowers can be single or in clusters, on stems up to 4 inches long
Leaves are divided into five to seven leaflets, sometimes three, and are oppositely arranged on stems
Stems grow up to 27 feet long and are slender and ridged
Seedheads are a rounded cluster of fluffy winged seeds (achenes); they look like pom poms
May be confused with the eastern Washington native Clematis ligusticifolia or the invasive old man's beard, Clematis vitalba but both of those species have creamy white flowers, not yellow
May also be confused with other cultivated yellow clematis species, especially Clematis tangutica. C. tangutica has brighter yellow flowers that are nodding and bell-shaped as compared with C. orientalis flowers that are more spreading or even curved back at the tips. Also C. tangutica leaflets are finely toothed on the edges.
Habitat and impact
Oriental clematis prefers riversides, rocky slopes, roadsides and similar open, sunny habitats with well-drained soils. Can tolerate semi-shady areas as well. This species can cover young trees and bushes, weighing them down and damaging them, as well as smothering and out-competing other vegetation. Plants will completely cover walls, trees, bushes and fences. The juice of freshly crushed leaves and stems may cause blisters.
Growth and reproduction
Oriental clematis flowers from August to September. It produces feathery, pom-pom like seed heads that persist and disperse over the winter and early spring months. Scrambling growth allows it to spread out vegetatively, and it can also spread by layering and sprouting from root crowns. Seeds are primarily wind-dispersed. Oriental clematis grows rapidly, at least three feet of growth per year from sprouts or existing stems. Its growth is very dense.
Control
Prevention: Oriental clematis is sometimes sold as an ornamental, so be careful to check the Latin names of plants you are buying to avoid introducing this species. If plants have seedheads, be very careful not to spread them when removing plants. It is best to control plants before they go to seed.
Small patches: Vines can be pulled off of trees and structures if it is safe to do so. Only the lower vines need to be removed because the plants need to be rooted in the ground. Remove any lower stems and pull them up by the roots. Discard all plant material in the garbage to avoid spreading this plant further.
Larger patches: Manual removal can be effective but for large sites it may not be feasible, especially on steep, rocky slopes. Several systemic herbicides are reported to be effective. Consult with your local noxious weed program or extension office for advice or follow the links below for additional information. Please refer to herbicide labels for site-specific control information and refer to the PNW Weed Management Handbook for additional information on herbicide use.
What to do if you find this plant in King County, Washington
Please notify us if you see oriental clematis growing in King County. Our program staff can provide the property owner or appropriate public agency with site-specific advice on how best to remove it. Also, because oriental clematis is not established in King County, we have an opportunity to stop it from spreading if we act quickly. We map all known locations of regulated noxious weeds such as oriental clematis in order to help us and others locate new infestations in time to control them.
Oriental clematis (Clematis orientalis) photos
Report oriental clematis in King County, Washington
Program offices are located at 201 S. Jackson St., Suite 600, Seattle, WA 98104. To contact staff, see the Noxious Weed Control Program Directory, send an email, or call 206-477-WEED (206-477-9333).
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