Growing Cannas, large and small. Canna lilies are wonderful in the garden. Growing fast, the full size selections quickly form a handsome large-leaved screen or an island of tropical-looking foliage from about 3 to 4 feet tall.. And then the show begins, and goes on for weeks and weeks. Huge, iris-like flowers begin to open, and before you know it, your canna lily plants have become the undisputed center of attention in your entire yard. They're really this spectacular, and a snap to grow. They're really wetland plants, and can grow in moist ground. Constant wetness isn't necessary, but water them often. Cannas are used as municipal plantings in many places like Miami. They are so good at taking care of themselves, they add great stripes of color in median strips, parks, and other places. So pick out a sunny spot in your garden or yard, and add cannas for the big show this summer.