Knotweed or Not?

kgw.com has this AP article describing the problems Oregon is having with knotweed. Unfortunately the common name "knotweed" is used to refer to any number of species, so the general reader will have no idea what plant the article is referring to. You can tell that whatever it is, it's invasive, it has hollow stems, and The Nature Conservancy wants to use herbicide injections to get rid of it. Luckily, your expert ISW reporter can narrow it down for you. They're likely talking about Japanese knotweed (Fallopia japonica or Polygonum cuspidatum). But they might also be talking about its gigantic but less common cousin, Giant knotweed (F. sachalinensis), or the hybrid between these species, F. x bohemica. Or maybe even Himalayan knotweed (Polygonum polystachum). All of these knotweed species are currently making their presence known in the Pacific Northwest. Whichever it is, best of luck to TNC on their control project.