Dear Tina,

Thank you for contacting Ask Extension regarding invasive species.

Clematis vitalba, often called Old Man's Beard or wild clematis, is considered a Class B invasive plant in the Willamette Valley. A Class B Listed Weed is:
A weed of economic importance which is regionally abundant, but which may have limited distribution in some counties (Table II).
Recommended action: Limited to intensive control at the state, county or regional level as determined on a site-specific, case-by-case basis. Where implementation of a fully integrated statewide management plan is not feasible, biological control (when available) shall be the primary control method. https://www.oregon.gov/oda/programs/Weeds/OregonNoxiousWeeds/Pages/Law.aspx

Do not confuse Clematis vitalba with the clematis variety native to Oregon. The native species usually has only 3 leaflets per leaf and flowers in spring, whereas Old Man’s Beard has 5 leaflets and flowers in summer. 

I have attached two pdf files with more information and some alternative species. I hope this information is useful. If you have any other questions, please write again. Happy gardening!

Dear Tina,

Thank you for contacting Ask Extension regarding invasive species.

Clematis vitalba, often called Old Man's Beard or wild clematis, is considered a Class B invasive plant in the Willamette Valley. A Class B Listed Weed is:
A weed of economic importance which is regionally abundant, but which may have limited distribution in some counties (Table II).
Recommended action: Limited to intensive control at the state, county or regional level as determined on a site-specific, case-by-case basis. Where implementation of a fully integrated statewide management plan is not feasible, biological control (when available) shall be the primary control method. https://www.oregon.gov/oda/programs/Weeds/OregonNoxiousWeeds/Pages/Law.aspx

Do not confuse Clematis vitalba with the clematis variety native to Oregon. The native species usually has only 3 leaflets per leaf and flowers in spring, whereas Old Man’s Beard has 5 leaflets and flowers in summer. 

I have attached two pdf files with more information and some alternative species. I hope this information is useful. If you have any other questions, please write again. Happy gardening!

Dear Tina,

Thank you for writing again to clarify which clematis species are invasive. 

Clematis paniculata is closely related to, and may be synonymous with, Clematis terniflora. Both are native to China and Japan and are often called by the common name Sweet Autumn clematis (as is the Clematis vitalba.) Due to the confusion surrounding common names, we prefer botanical names which are more precise. In this case, there are actually several clematis species that are synonymous with C. paniculata. 

While not classified as invasive in Oregon, C. paniculata is considered invasive in many parts of North America and is listed as such in the Global Invasive Species Database. Further, the leaves and sap are poisonous:

Clematis can cause severe mouth pain and ulcers if eaten. Toxic to dogs, cats, horses. Clinical signs are salivation, vomiting, diarrhea. In humans, symptoms may include dizziness, confusion, fainting, and convulsions. Fatalities are rare, due to the rapid and intense bitter taste and mouth irritation from eating. Gastric lavage is recommended and anti-inflammatory to soothe irritated tissue. Contact dermatitis results in skin redness and burning sensation for some people, gardening gloves are recommended.
Poison Toxic Principle: protoanemonin
Causes Contact Dermatitis: Yes
Poison Part: Leaves, sap/Juice
-- http://www.iucngisd.org/gisd/species.php?sc=1224

If you are specifically interested in clematis, I suggest you look for the species native to Oregon, the Western White Clematis (Clematis ligusticifolia). You may be able to locate this plant through local native plant societies or Oregon growers.

I hope this answer is useful. Feel free to write again if you have other questions.