Japanese knotweed - Polygonum cuspidatum (aka Fallopia japonica). A very serious invasive species across much of the country. And extremely difficult to eradicate.

Here is a link that might be useful: Japanese knotweed

Thank you. That is definitely it. I actually don't mind where it is because it blocks the view of our house in the summer BUT I have noticed it is hard to eradicate. I don't mind it if it stays within the boundaries where I want it. I haven't tried any chemical means to get rid of outskirters but I have tried ripping the roots and mowing in the past and it doesn't die.

Read up on this plant. It is an invasive menace. It's so bad in the UK there are laws about it! It's treated like toxic waste. Any prunings however small have the capacity to reproduce. Nothing grows under it and it can oust natives and block watercourses.

Here is a link that might be useful: JK

Well, that is 2 invasive species on our property - the other is Oriental Bittersweet. That has taken a hurting to my cutting the crap out of it though. Knotweed sounds worse than Bittersweet..bad news.

It is worse than Bittersweet especially since it's roots can extend 5' deep. The only thing you can do is to keep pulling it out whenever you see it. If you have a lot of it, as my mother did on her property, cut it down, than in the fall dig the whole are up, then cover the area with heavy black plastic and leave it in place for a year or longer. That was the only thing that got rid of this scourge on her property. I don't recommend broadleaf killer since it it way too dangerous to use. It can kill humans and animals. Just not worth it.

When you say "broadleaf killer" you are referring to glyphosate or triclopyr?