Floral, you are right to warn gardeners about using any forms of purple loosestrife here (horticultural as well as wild) in gardens. Perennials.all, I do have a good idea of the distribution of wild purple loosestrife in Ontario and elsewhere in North America. I think you missed the point of my post. The 1992 Manitoba Study took plants of the horticultural cultivar 'Morden Pink' and planted them near a river and adjacent to wetlands, both of which had wild purple loosestrife present. The furthest any of the cultivar plants were away from wild purple loosestrife was 200 meters. 'Morden Pink' was thought to be sterile. It was presumed that the ability of plants of the cultivar to self-fertilize themselves, in the way the wild type does, had been bred out of them; namely that they were "self-incompatable". In fact, it was found that the cultivar plants lost their self-incompatability (hence sterility) in these locations in the presence of the wild type and, like the wild form, produced very large numbers of seeds. Some gardeners then wondered whether there was any evidence for sterile purple loosestrife cultivars losing their self-incompatatbility in garden situations, when the gardens were located nowhere near wetlands nor wild-growing purple loosestrife. Some simply dismissed this question out of hand. Either you believed in "the purple plague" or you didn't. Personally I'm more impressed by evidence. Are the researchers correct in extrapolating from purple loosestrife cultivars placed in research locations to those in average gardens? Over the years, I've seen almost no relevant evidence presented by gardeners. My post presents such evidence; that is seedlings which have been produced by one plant of a horticultural purple loosestrife cultivar that lost it's self-incompatability in a garden.

It is not knotweed......and it does look like a tree seedling (root shoot), what type I am not sure. But you will get faster and accurate ID's if you use the forum - Name That Plant - that is intended for plant identification. This is not the right place :-)

gardengal48 ........Whether it’s the Houzz app or working in a browser, there is very little here that works properly (although it’s certainly easy to make a purchase...surprise, surprise). This is by far the most frustrating app and website I’ve ever dealt with. And contacting support is completely fruitless. They don’t even respond anymore. So sad because they have a great opportunity for a fantastic site and app but no one seems to know what they’re doing and every change and update just brings new problems on top of the old. Can you hear my frustration :) I tried the Gardenweb link and it still did not work.

There's a dedicated plant identification forum here on garden web. Name That Plant Forum. It's frequented by humans who have proved far more accurate than any app. Meanwhile, have a look at Cyanchum rossicum. Since you're in NE USA that could be it. And it's not something you want. But please post on NTP. You'll get a lot more answers there.