Perennials need regular digging, dividing and transplanting to maintain healthy, attractive growth. When the middle of a plant dies out or looks like a doughnut, or if plants start to flop, fail to bloom or outgrow their location, they need to be divided.
Division is a good way to create new plants for yourself or to share with friends. Some fast growers are so productive you may need to toss the surplus in the compost bin.
How do you know when to divide? A good starting point is to follow this old saying: “Divide spring bloomers in fall, fall bloomers in spring, and summer bloomers in either fall or spring.” You can generally stretch the transplanting guideline with most perennials as long as you provide proper care afterward. Here’s how to dig in:
Dig around the outside edge of the entire plant using a garden fork or shovel, and lift the plant out of the ground.
Each plant can be divided into halves, fourths or eighths, depending on its original size and how many divisions you want. Two garden forks or shovels, back to back, are usually sufficient to divide the sometimes stubborn clump of roots.
Amend the planting sites with slow-release nitrogen fertilizer and organic matter. This is one of your only chances to deeply amend the garden soil around perennial plants.
Replant divisions at the same depth they were growing. You may want to put one of the divisions back in the original location. But don’t replant the center of the plant if it’s dried-out or dead. That is better suited for the compost bin.