That's a native plant I just discovered going thru a local native park here in Jacksonville. I was helping the Native Plant society clean up the park and they had too many of these things, so I took some plants and seeds and planted it in my garden, but because it was the end of the year they never grew, but luckily they started popping up in the spring.
It's suppose to be a super pollinator attractor, so I got it to help out-compete with another super pollinator plant that can become very invasive (Spanish Nettle) and take over my garden.
The scientific name of the plant above is Melanthera nivea (AKA: Snow Squarestem) As the common name implies, its stem is square, but it's not in the mint family, rather it's in the aster family.
http://www.regionalconservation.org/beta/nfyn/plantdetail.asp?tx=Melanive
