If we are looking for something with a roundish leaf it won't be Ipomea aquatica (Kang Kong) - it has a long narrow leaf, I grow it, handy hot weather green after the lettuce have all bolted. I also grow a very pretty Nymphoides - it came to me as 'montana', floating round leaf, lovely yellow fringed poppy flower. Terry Frewin Strathbogie Ranges, NE Victoria, Australia hot and dry, mid 30's (C) today, 40 last week, yuk