This plant was found next to a pond, under a juniper bush. It has a square stem and opposite leaves, just like a lamiaceae, and even smells a tiny bit like mint when I crush it. However, the leaves are smooth with entire margins, which is not normal for lamiaceae plants as far as I know. It also has two points on the back of the leaf that remind me of ipomoea.
Edit: Crashdive123 suggested adding in some more information.
This is central Alabama, zone 7b, taken just yesterday (Feb 6). It's on my college campus, in the soil on the other side of a concrete wall enclosing a tiny "lake." The soil was very moist underneath a thick layer of pine straw (3 inches or more). There are no flowers and no woody parts, at least not yet. I believe it is new, within the past month, but it could be growing back from last year. Each stem goes (almost) straight up, and they're on average a foot high right now.