Polly - Nope! No soil at all. Just that clay kitty litter. Don't use other kitty litter though. Only the red bag one. Other kitty litters have other additives that might kill the water lilies.
The past couple of years we've had such cold temps during the Winter that I lost all my water lilies except the Mexicana and maybe one other hardy. I had ice covering the tops of both of my pre-formed ponds and all my water containers. Luckily, my Lotus came back, but all my water lilies didn't except the Mexicana and maybe one other yellow blooming hardy, too. I had some really nice tropical water lilies, but lost them all. I had all the hardies in one container and all the tropicals in another. Only the yellow blooming hardies came back.
When I pulled up the pots in late Winter/early Spring, there was nothing except rotting roots in the tropical water lily pond. It really was a bummer! I live on the east coast of central Florida, so you'd think they would've been okay here, but they weren't. The Mexicana did indeed spread and make new babies. I will continue to keep that cultivar because it has been reliable for me and it is perfect for my pond fish. Even when the temps were freezing for days and then warmed up shortly after, the Mexicana started putting out pads. I was amazed! And they started blooming in March! I do think they could be invasive, so that is why I have them separated from all my other water lilies. They have their own pre-form pond to go wild in! I rarely fertilize them. Throwing in a pond tab or two occasionally. The fish swim around them and I can still see them because the pads raise up above the water yet hide the fish from birds flying overhead. They also cover the entire small round pond and help shade the black pre-formed pond from the heat of the sun. The water is crystal clear too. I believe the water lilies help keep the water clean. To me they are the perfect water lily if you want fish in a pond. But I have too many at the end of each year, so I need to either toss some in the trash or find new homes for them. They are so easy to care for! I just let them go wild in the pond.
Another positive thing about them ... I get lots and lots of tadpoles which will eat my water lilies. The Mexicana grow so fast that I never hardly notice all the missing and eaten pads, unless I look down into the water and see the tadpoles eating them. LOL! My Mexicana pond always looks the best! :-)
I do love the tropicals though. So do the tadpoles! I get in on the Cubits group co-ops through Texas Water Lily and get them so cheap that it doesn't matter if I have to replace them every year.
http://texaswaterlilies.com/
