Nothing brightens a garden more than an abundance of dahlia blooms. Dahlias, a genus of perennials, bloom 2- to 10-inch red, pink, yellow, white, orange or purple spiky flowers, depending on the variety. With proper pruning, the lovely blooms can decorate the gardens of U.S. Department of Agriculture plant hardiness zones 8 to 10 from mid-summer to first frost. There are a few types of pruning that will control flowering and plant shape and size: deadheading, disbudding and disbranching. Pruning may even help encourage larger blooms, which are particularly excellent as cut flowers.
Bend a few lower lateral branches downward carefully until they break away from the main stalk. Laterals are the stems that grow from the main stalk, and the best time to disbranch them is when they begin developing buds. Disbranching will encourage larger blooms, help control the shape and size of the dahlia and prevent diseases. Keep three to five laterals on large varieties or five to eight laterals on medium varieties.
Pinch off side buds around the primary bud when they are pea-sized, removing them to down to an axil. The primary bud is normally between two small buds. Look further down the same stem for two more buds, and pinch them down to an axil. Disbudding will encourage growth of the primary bud and more but smaller side buds.
Inspect the dahlia for spent flowers; they normally look like cone-shaped buds. However, do not mistake spent flowers for buds, which look flattened at the top and rounded overall. Cut off spent flowers at the end of their stems with by-pass pruners. Removing spent flowers before they go to seed will encourage the dahlia to flower more.