Snapdragons (Antirrhinum majus) add charming to flower gardens, with their blooms resembling the snapping jaws of their namesake mythical beast. Although they are usually grown as annuals, some varieities of snapdragons can survive as perennials in U.S. Department of Agriculture plant hardiness zones 7 through 10. Lightly pruning the plants throughout the growing season encourages an ongoing flush of flowering, while a fall trim helps prepare perennial plants for winter.
Cut back the flower stems when the majority of the blooms on the stems have wilted. Remove the stems near their base where they emerge from the foliage.
Shear back the entire plant by up to one-third of its height when flowering diminishes in midsummer. Cutting back severely forces a new flush of compact growth and encourages the growth of new flower stems and buds.
Sprinkle 1/3 pound of 10-10-10 fertilizer over every 25 square feet of snapdragon bed, applying the fertilizer 6 inches from the base of the plants, after shearing them back at midsummer. Water the fertilizer into the soil following application.
Trim out any dead or damaged leaves at any time during the growing season. Cut off the leaves where they join the main stem.
Prune perennial snapdragons to the ground when they die back in cold temperatures. Spread 2 inches of mulch over the bed to insulate the snapdragons from temperature fluctuations.