Suggested Perennial Plants to Prune in the Spring

Gardeners in warm climates can treat fall, and sometimes even winter, as supplemental growing seasons. But for gardeners who experience hard winters, fall is a great time to get a head start on garden clean-up. We hear a lot about four seasons of interest in the garden, but this rarely applies to perennial plants. Most perennials turn ugly as the temperatures drop.

However there are a few that remain evergreen, especially in milder areas. These can be left standing for interest as well as to fuel the vigor of the plant. And there are perennials that simply don’t fare well if they are pruned too late in the season.

The following list is a recommendation of plants that are best pruned in spring. There will, of course, be exceptions. Any plant that is diseased, infested, or otherwise in poor condition, should be pruned in the fall. Consider this listing and the complementary Plants to Prune in the Fall, as guidelines. You will learn what works and what doesn’t, for your own garden.
Suggested Perennial Plants to Prune in the Spring
    * Artemisia Most Artemisia don’t like being pruned in the fall. The growth that results is too tender to survive the winter and the dieback is often enough to kill the whole plant. Clean in early spring. (USDA Zones 5 - 9)

    * Asters Fall blooming asters have generally been pinched and forced several times throughout the growing season. Once they are finally allowed to bloom, they appreciate being left alone to recuperate, until spring. Several bloom so late into the fall, the question of fall clean-up becomes moot. (USDA Zones 4 - 8)

    * Astilbe Astilbe don’t require much maintenance. Fall clean-up is unnecessary and may weaken the plant’s tolerance for cold. Minimal spring clean-up is required. (USDA Zones 3 - 8)

    * Balloon Flower (Platycodon grandiflorus) If pruned for sturdiness, Balloon flower blooms late in the season and remains attractive until frost. Since it is late emerging in the spring, it helps to leave the old foliage as a marker. (USDA Zones 3 - 8)

    * Basket-of-Gold (Aurinia saxatilis) Although Aurinia fares best and lives longer if sheared back after flowering and not allowed to go to seed, the foliage can be evergreen in mild winters and there doesn’t seem to be any benefit to cutting it back until spring. (USDA Zones 3 - 7)

    * Bear’s Breeches (Acanthus spinosus) You may need to cut back old, dying foliage throughout the growing season, but the new healthy growth remaining in the fall could well remain evergreen throughout the winter, depending on weather conditions. (USDA Zones 6 - 10)

    * Black-eyed Susan (Rudbeckia fulgida) Although not particularly attractive in winter, the seed heads will feed the birds. (USDA Zones 3 - 9)

    * Blue Mist Shrub (Caryopteris) Caryopteris bloom on new growth. Cut back to 6-8 inches in the spring. Newer varieties, especially, can be very sensitive to cold and shouldn't be cut back until buds begin to green. (USDA Zones 5 - 9)

    * Butterfly Bush (Buddleia davidii) To lessen winter kill, wait for signs of green at the base and then cut back to 6 - 10 inches. (USDA Zones 6 - 9)

    * Butterfly Weed (Asclepias tuberosa) Although Asclepias is a prolific self-seeder and should be deadheaded if dozens of new plants are not wanted, it winters better if the foliage is allowed to protect the crown. (USDA Zones 4 - 9)

    * Campanula Most campanulas get sheared back at some point during the summer, to clean up ugly or damaged foliage and encourage another flush of blooming. Fresh basal foliage will result and should be left through winter, so as not to encourage more tender growth in the fall. (USDA Zones 3 - 8)

    * Cardinal Flower (Lobelia cardinalis) Although Cardinal Flower likes moist soil, it doesn’t like sitting in cold, wet soil all winter. Leaving the foliage and flower stems in tact protects Cardinal Flower from some of the ravages of winter, so hold off clean-up until spring. At that point, you can trim the damaged areas or simply cut back to the ground. (USDA Zones 3 - 9)

    * Coral Bells (Heuchera) Heuchera are prone to heaving in soils that freeze and thaw. Leaving the foliage in tact helps to mulch the plants through winter. (USDA Zones 4 - 9)

    * Cushion Spurge (Euphorbia polychroma) In warmer climates, Euphorbia can actually become a shrub and it’s fine to leave the plant alone until spring and then clean out the dead foliage. In colder climates, simply cut the plant back to its base in the spring. (USDA Zones 4 - 8)

    * Delphinium If you’re lucky enough to grow Delphiniums as perennials, remove the flower stalks, but allow the foliage to remain until spring. (USDA ones 3 - 7)

    * Dianthus Most Dianthus can remain somewhat evergreen throughout the winter and nothing is gained by cutting back in the fall. They will still need some clean-up in the spring. (USDA Zones 5 - 8)
Collected from- http://gardening.about.com/od/maintenance/a/Spring_Pruning.htm