Bachelor's buttons (Centaurea spp.) brighten the garden with their small blue, yellow, white or pink flowers. Each small flower is surrounded by a fringe of delicate bracts that add further texture and interest to these quaint blooms. Many garden varieties grow as annuals, although there are perennial bachelor's buttons that grow in U.S. Department of Agriculture plant hardiness zones 3 through 9. Pruning the plants lightly throughout the flowering season encourages them to continue blooming throughout the warm summer season.
Pinch back the top 1 inch of each stem when the bachelor's buttons are approximately 6 inches tall. Pinch just above the topmost bud or leaf. Pinching forces the plant to branch, which creates a more compact plant that produces more flower buds.
Cut off dead blooms as soon as they begin to wilt. Cut through the stem beneath the flower just above the topmost leaf or bud, using small pruning shears. Cutting off the spent flowers, or deadheading, prevents seed formation, which encourages the plant to produce more flowers.
Prune back the entire plant at midseason if it becomes leggy or begins to flower poorly. Cut the bachelor's button back by up to one-third of its height to encourage a flush of new growth and flower bud production.