Can someone please help me identify this plant? I'm assuming it's a weed...
After I enlarged your photo, I think the plant is Bloody Dock or red Veined Dock, Rumex sanguineus. It is related to curly dock, Rumex crispus, and the caption information that came with it states that it is in the polygonaceae family which is one of the family of plants that really spreads. The Bloody Dock has the red veined leaves and they are used in salads. The photo that I found was attributed to Burpee, the seed people. I would guess that it is in the Burpee catalog and used for a salad green. The information also stated it was for zone 6a to 8 which means that is is only marginally hardy here in the central Ohio area.
My best quess is that it came along with the tree that has been planted in that area. If you don't like the Red Veined Dock, you probably could cultivate around and it would die off. Surely the easiest thing to do would be to cultivate and get rid of the now growing plants and then mulch lightly the entire area. If any new plants emerge, then it would be rather easy to take care of them too. I would not let it go to seed as this would make matters much worse.
You also might try it in a salad. If it is tasty, then harvest some for salad and you know that after you do that it will die off and be difficult to grow!!
I would also take a dug up plant or two to a full service garden center in Columbus. A lot of them hire trained plant people these days and would be able to identify the plant. I can only take an educated guess from your photo. Hope this helps. Don