Chinese Water Chestnut Plant (Eleocharis dulcis)
5/21/18 Update : These are over 18" tall and ready to be planted!! These ship very well and grow even better, if you have any problems with them at all don't hesitate to let me know!
These plants grow and spread so quickly, one plant can fill a 6' space. It's important to give these a nice long growing season to get large corms, but you don't have to live in Florida. I'm in zone 7b south east Virginia and they have come back year after year without replanting for multiple winters with record cold temps. So I believe they are much hardier than other websites say.
Plant these anywhere that can hold water. The optimum soil temperature for planting is 55-60*F. It is recommended to keep the water depth between 4-8" and a minimum soil depth of 10-12".
Leave them flooded all season, and you can harvest after the green tops turn brown in the fall, you don't have to rush to beat a frost, they keep fine in the mud, but don't let the ground completely freeze before harvesting.