This plant was growing like a vine within an evergreen I have. The thickest part of the stem was about .33 inches wide and it was woody. From that there were lighter green stems that branched. Attached is a picture of the leaf (with a $1 bill for scale). I cut it and pulled it out from the evergreen.
This vine bears a resemblance to Porcelain berry or Amelopsis brevipedunculata. It is native to Asia and a positive identification would be the blue berries that are prominent in the fall. The leaves are variable in size and shape but larger ones have the prominent lobes in your picture.
From a positive description in a seed catalogue I bought a packet of seeds and got one seedling. For a few years it didn't do much. Then...it all changed. One season it grew to ten feet wide, the next season it was twenty feet wide and fighting the rose bush and the cedar. The berries were attractive until frost but poisonous to dogs.
There is a reason this plant is considered an invasive pest across North America. It is more vigorous than any plant has a right to be. Seeds in the berries are spread by birds and every berry sprouts a few seedlings.
This plant became a nightmare in my garden and took hours of work to remove. Two years later I am still removing the seedlings.
