This weed pops up in one area of the garden, but the thing that worries me is that I have never been able to pull up a root. No matter how deeply I plunge my shovel I can't find the root, and when I pull the weed it is a single thick stem way deep down, and is ALWAYS broken off from some other root structure underneath. I have no idea where that root structure is located, but I'm thinking it goes all the way down to the mantle layer below Earth's crust. It does respond to RoundUp, which I am forced to use, but I'd like to know what it is so I can have an idea of what my future with this thing is going to look like. A distinctive part of it is the new growth on top, which is very small, a grey color, and looks soft and droopy. It has a central stem, and no offshoot branches, almost as if it wants to be a vine.