It sounds like your problem is the medium. Sand is not helping. See “Planting” advice above, which reads in part: Exotic, tropical creatures, cannas need lots of sunshine and fertile, moist soil but you don’t have to pamper them. To plant, loosen the soil to a depth of 12 to 15 inches, then mix in a 2- to 4-inch layer of compost. Dig a hole 2 to 3 inches deep and set the rhizome in the hole, eyes up. Cover with soil and tamp firmly. Water thoroughly. We hope this helps! Reply
It sounds like your problem is the medium. Sand is not helping. See “Planting” advice above, which reads in part: