Asters are fall blooming perennials that are native to North America and Europe, according to Dr. Leonard Perry of the University of Vermont. Salvia, also known as sage, is a perennial with a high drought tolerance that is native to Mexico and South America, according to Nature Hills Nursery. Like all perennial flowers in a garden, asters, salvia and other flowering plants need to be pruned to maintain their heath. In some cases, pruning perennials even causes them to rebloom.
Deadhead the spent blooms of any perennials as they occur. This will allow the plant to flower again and keep it from self-seeding. Deadhead salvia in the late spring and asters in the fall. Cut back the spent flower stalk to just above leaves.
Cut back salvia and other spring blooming perennials by half in the early summer.
Cut back asters and any stalky fall blooming perennials by half in the early summer. They will have time to regrow for flowering in the fall.
Remove any dead, damaged or diseased foliage from flowering plants as they occur.
Cut back asters, salvia and other flowering perennials to the ground after their foliage dies back in the late fall.