Baby Plum Tree

This looks to me like a plum seedling. I planted seeds in this pot in June. No expectations as to germination. These were not pits that I removed seeds from - separate batch - an the seeds were mailed to me from a friend in Georgia. They are a wild, native yellow plum. I'm surprised it did not need stratification, and I don't know how to manage it through the winter, but shouldn't be too difficult. That's assuming it's really a plum and not a weed. Does look plum-like.