Are they cold-hardy?

I have two large fresh water ponds and one sal. planted lotus in the fresh watervpond and in two years hasd to have the taken out at a cost of six hundredv dollars,they are beautiful' if I were to grow them in a pond I would,grow them in large containers with no holes, thats how I grow mine I have seven large contaiers and fiberglass ponds that I growvthe lotus,hardy and tropical waterb liles in,since you are in zone 7 they might not make it through the winter in your pond but dont count on it,ive got somt hardy waterlilies for trade and in my opion the nicest lotus Shiroman, if you want to buy go to Teaxas Water lily, they are who I buy mine from LOL Hightider