These plants have an irritating smell and are resistant to roundup and other chemicals. They are found in my back yard which is partially shaded. They grow into longer vines that spread very quickly. I’ve tried digging them up and they have relatively shallow (<6 ” depth) root balls that extend out several feet or more connecting them to the other plants. As they mature they grow white flowers as seen in the last picture which was from at least a year ago.
this is one of the non-native Clematis species. It is most likely Clematis terniflora, from Japan, but it may also be Clematis paniculata, from China. Both are invasive. See this site for more information: https://plants.ces.ncsu.edu/plants/clematis-paniculata/ I am familiar with the first one but not the second one. While many Clematis are planted for ornament, this one is not recommended.
Dr. Steven Hill, Botanist, SCNPS