I've got some Frog Bit that i got at a LFS. It is growing really well and I was wondering if it is hardy in N.Illinios. The guy at the store said it was, however I have yet to find it in any of my pond books.
Well, it is classed as an invasive weed in Maine and Vermont and as a quarantined wetlands plant in Washington state so if it survives there it should be fairly hardy. Check your local regulations on use though. Also google it under Hydrocharis morsus-ranae