When Can a Canna Tuber Be Too Brown to Plant?

Choosing Tubers

• It's not the color of the tuber that you necessarily need to worry about. A canna tuber can be light or dark brown and still be perfectly healthy. Instead of worrying about the color, give the tuber a squeeze: It should feel firm all over. Tubers that are rotten have soft spots. These spots may be darker brown than the rest of the tuber, but again, the color is not as important as the texture. The healthiest tubers are firm to the touch, without obvious rotting spots or other signs of disease such as flaking skin or fungal growths.

Canna Tubers

• Cannas can be grown from seeds, but most home gardeners grow them from tubers. Canna tubers produce roots and sprouts. The sprouts grow from buds found in the old stem base. When choosing a tuber, look for one that has a stem base that looks healthy -- not soft and rotten. Roots sprout from the bottom of the tuber. Plant the tubers about 3 inches below the surface of the soil, with the stem base on top. Because they spread, be sure to leave at least a foot of space between each tuber.

Canna Culture

• Cannas are hardy in U.S. Department of Agriculture plant hardiness zones 8 through 11. The cold, wet temperatures in cooler climates cause the tubers to rot, but that doesn't deter many home gardeners from growing them. Canna lovers in cooler climates simply remove the tubers from the ground before the first frost of autumn, and replant them in the spring when the weather warms up. Cannas adapt to all types of soil as long as it is well-draining, but grow best in rich, fertile soil and full sunlight.

Other Considerations

• Choose tubers according to firmness and overall appearance, but also consider size: The larger the tuber, the larger the canna flower. Many cannas are big and showy, but some are small and attractive in a quieter way. These are usually marketed as dwarf cannas, and most remain under 3 feet tall. Standard cannas can grow to more than 6 feet. All range in color from creamy white to bright scarlet, with yellow and orange blooms as well. The leaves are as striking as the flowers: Broad and long, they often present with ruffled edges, and in shades of bronze, red, green or variegated. Cannas tend to bloom late -- they bloom best during long, hot summers -- so if your summer is cooler than usual, take heart in knowing that at least you can enjoy the beautiful foliage.