We are new to Dallas and have several Canna Lilies in our backyard. They are about 3-4 ft high. Are you supposed to deadhead the flowers once they die off? Are you supposed cut the plant back in the fall or spring, or just leave them alone? They get direct sunlight where they are located.
Dead heading your lily's can help with appearance and promoting more flowering.
Just pinch off the spent blossoms.
Here is some links for you.