Hello, My first post. I was asked about an "invasive" plant growing on a neighbour's property...the main bush was cut down a year ago, but there are shoots coming up from runners, including up through gaps in the concrete walkway. Any help in identifying the plant would be appreciated. As the main stem was cut off, only the shoots remain: the oval-shaped serrated leaves are oppositely arranged, with 1cm long spines where the leaflets attach to red-colored stems, and also spines on the stems themselves. Thanks.