Do the leaves resemble any of the trees? Looks like some kind of baby tree, maybe mulberry but pic is too small to know for sure. Pull them out as soon as you see them.

Thank you for replying. No, the leaves do not resemble any trees around. I pull them up, but, they come back faster than I can keep up with the growth of the new ones. I also try to get as much of the root as possible. I've been using Round Up, but, I cannot get too close to the other plants with that method..

The leaves of immature mulberries are, IME, different than those on the mature trees. Could you get a closer shot of it? Are the roots bright yellow? Are the plants sort of woody?

I have identified the weed to be the Mulberry Weed, Fatoua.
Now to find out how to eradicate it!!