• Tuberous root
• All zones
• Full sun, partial shade where summers are hot
• Regular watering during growth and bloom
Blooming from summer through fall, dahlias are available in numerous colors and floral forms. Flower diameter ranges from 2 to 12 inches; plant height varies from about a foot to over 7 feet (stake varieties that grow more than 4 feet tall). Plant after the last frost in spring, setting roots 4 to 6 inches deep. Space tall varieties 4 to 5 feet apart, shorter ones 1 to 1 1/2 feet apart.
Though roots can be left in the ground where winter temperatures remain above 20 degrees F/-7 degrees C, gardeners in most areas prefer to dig them annually. After foliage yellows in fall, cut back stalks to about 4 inches. Dig clumps of roots and let dry in the sun for several hours. Then place in single layers in boxes, cover with dry sand or sawdust, and store in a cool spot over winter. In spring, divide (if needed) and replant.