This plant is now about 5 feet tall, grew fairly rapidly this year. So far, it has a single stalk. I wonder if it's a tree sapling, a shrub of some sort or a weed (undesirable plant). It came up volunteer. The large leaves are very unique and got my attention. That's a 6" ruler in the photo.
Part way down the page, the leaves are almost identical. We have some mulberry trees on the property, but they all have the large, more rounded leaves, not the lobed ones I inquired about. I'll pamper this tree since I love mulberries!!
Mulberry leaves are quite variable, that's probably why they don't look exactly like the leaves on your other mulberry trees. I wonder though if it's really red mulberry (M. rubra) or if it's M. alba instead. I believe M. alba is the more common weedy variety and would be more likely to be popping up on its own. http://davesgarden.com/guides/pf/go/56629/ If you wait until the morning I'm sure the tree experts will be along and will have more to add to the conversation to help you figure out which kind you have.