The perennial garden is a continuous source of tinkering. Gardeners will move plants from one area to another, replace those plants that didn't perform up to expectations, and thin those whose performance was more than ever dreamed possible. Sometimes the perennial bed needs more than just a cosmetic make-over. There are times when a complete renovation is in order. Perennial weeds such as quackgrass may be more numerous than the desired perennials, the soil may need improvement, or the gardener may have a new design in mind.
Renovating a large perennial garden is a big job. It can be done in either spring or fall. In the spring, try to complete the project before the arrival of hot, dry weather. The months of April and May are excellent. In the fall, late August through September is optimal. Begin the renovation process by digging up all the plants in the bed (with a few exceptions). Cut a circle around the crown of the plant with a trowel or spade, then pry the roots up and out. For large perennials it is easier to cut the plants into manageable pieces when they are still in the ground. Don't remove shrubs unless their presence isn't part of the new plan. Some perennials prefer a certain season for division or transplanting. If you are renovating at the wrong time for these plants, it is better to work around them. After digging set the plants on a plastic tarp spread out in a shady, protected location. Keep the same plants together in groups and label them (even the best of minds forget where they put things). Water the plants as weather conditions warrant to prevent them from drying out. Under good conditions, most plants will survive out of the ground for a few days without any problems.
After the plants have been removed from the bed, carefully remove all weeds, and rake the soil level. If necessary, amend the soil by spreading a 2 to 3 inch layer of organic matter such as compost or peat moss. Sprinkle on the needed fertilizer and other amendments. Then using a shovel or fork, turn over the soil to mix in the amendments. Work backwards to avoid walking on and compacting the prepared soil. When you're finished digging in the materials, rake the area level again and clean the overflow soil from around the edges.
Once the soil is properly prepared the plants can be replanted in their proper locations. Many perennials will not require division; however, this is an excellent opportunity to do so if necessary or if you are looking for more plants of that particular variety. Remove soil from the roots by shaking vigorously or washing the roots off with water. Removal of the soil allows a better view of the crown and roots for division. It is also the only way to remove grass and weeds from within the perennial clump. Perennials require different techniques and tools for division. Some plants can be pulled apart by hand, others require a sharp knife, still others a sharp spade.
After division, set out the plants on the soil and arrange them according to your garden plan and taste. Make sure to allow adequate space between plants for good growth, maintenance paths, and annual flowers you want to use. Once the arrangement is to your liking, begin planting. If the sun is shining and temperatures are warm, make decisions on plant placement and planting quickly to prevent the plants from drying out. Actual planting goes quickly once you start. Set the plant in the planting hole so the crown of the plant is even with the soil level of the bed. If you are adding new container grown material, break up the root ball or if badly pot bound make vertical cuts in the sides of the root ball with a knife before planting. This helps the plant roots grow out into the new soil quickly.
The final step is the addition of mulch and water. Add 2 to 3 inches of organic mulch such as wood chips, shredded leaves, or compost to conserve moisture and prevent weed growth. Water each plant thoroughly immediately after planting. Water the entire bed weekly if rainfall isn't adequate. Before you can call the job complete, there is always clean up to do. Extra plants will need to find a new home, either in another garden in your yard or the gardens of friends and relatives. Compost unwanted plants and debris. Renovating a perennial bed is a big project. However, the improved appearance of both the plants and flower bed are worth the effort.
This article originally appeared in the May 18, 1994 issue, pp. 1994 issue, pp. 71-72.