I agree with HamiltonSquare, that they defintely resemble the first year leaves of Rudbeckia triloba. They are coarse , rough and hairy, when they first emerge, like most of their R. fulgida and R. hirta relatives. R. triloba is a biennial, blooming later in it's second year. At least that's how it behaves in my Zone 4 to 5 garden. I also have too many seedlings and will have to take a few of them out.
The young Sorrel leaf also has three main lobes, but is smooth to the touch, and if you bite into it, it has that definite lemon sour tang.
