conollyana (Fallopia ×conollyana, railway-yard knotweed)
The interspecific hybrid between Japanese knotweed and the common Russian vine, Fallopia japonica × F. baldschuanica. Japanese knotweed bears viable seed of this hybrid, confirmed by artificial hybridization in 1983, but uncultivated mature plants were not discovered until 1987, in the Railway Fields local nature reserve (formerly a railway goods yard) in the London Borough of Haringey. The growth habit of the hybrid resembles that of Japanese knotweed. It is not very aggressive but grows to 2m in height and in time can develop into large stands.