Cannas have banana-like foliage and large exotic blooms, which are available in a plethora of colors such as red, orange and yellow. They add a tropical look to gardens, even in the coldest climates.
While cannas require the same general care in September as they do during the previous months, there are some tips to help your cannas in cooler zones prepare for and survive through the winter months so they can bloom again the next year.
Apply about 2 to 4 inches of mulch in late September in zone 6. Use organic mulch such as leaves, straw, wood chips or bark. Mulch helps keep the soil warmer during the winter months so you do not need to dig the bulbs (which are actually rhizomes) up in zone 6. In colder zones, you will have to dig them up after the first killing frost.
The canna foliage is usually left alone in September. As long as the leaves are still green, they are soaking in the sun and converting it into carbohydrates through the process of photosynthesis. Cannas will then store the carbohydrates in the bulbs for the next spring. However, once the foliage withers and browns, usually in October or November after the first killing frost, cut it back to about 4 inches above the ground. If you live in an extremely cold climate, this may happen in September.
Dig up your cannas in September if the killing frost has occurred in your climate (e.g., zone 1 or 2). After you have cut back your foliage, use a garden fork to dig up the canna bulbs, which are usually just 2 inches below the soil. Then dry the bulbs for a few hours and store them in a mesh bag, open box or similar ventilated container in a cool (40 to 50 degrees F), dry location.