There's an invasive vine in my yard, actually all over this area (southern NH, northern Ma.) which is extremely agressive. It looks just like a bittersweet but is green without the woody stems and bears no berries or flowers of any kind. It pops out all over the lawn, sends twining tendrils toward any upright structure or hedge, grows rapidly. I have not been able to find it online after days of searching and am curious to know what the heck it is, because it's so common in this area.