I cleaned my pond. The roots on my lily are massive. Can i cut them back without killing or damaging it?
Sounds like they need dividing and now is a perfect time to do it. Remove the pot from the pond and then remove the lily. It probably has jumped out of the pot by now. If you have to, cut the pot off. Now hose the soil off the roots until you can see tubers. Start separating them. You will most likely have dozens of them. Choose the largest and repot them in something like a dishpan or that size. Trim off the dead pads. Fertilize and put them back in the water. If you want to save corms for friends, just throw them in the pond unpotted and they will be fine until you give them away. They won't grow, but they won't die. The lilies will now flower better and be healthier.
Put this on your to do list for every spring.