Perennials give gardeners a few signs that division is needed. A dead center may form in the crown area with a ring of plants around the perimeter, blooms are fewer and smaller, and growth appears crowded. How do you know when to divide? A general rule is to divide perennials in their non-bloom season, with mid-summer bloomers being divided in spring. Spring bloomers are divided in late summer/early fall, and late summer/fall bloomers are divided in spring (when new growth is just a few inches out of the ground). Use a spading fork or spade to dig the clump and cut off divisions. If you don't want to divide an entire clump, sections can be cut from the edge of the clump with a sharp knife, pruning shears dedicated to division (you will damage your good pruners), spade, or sharp trowel. Some plants have tough, thick root systems that are challenging to divide, including hosta, daylily, astilbe, and a few others. After replanting, water to establish the roots. If you divide perennials in late summer or early fall, apply three to four inches of mulch over the transplants after the soil freezes. This is to prevent soil freezing and thawing, which can heave plants out of the ground. Check plants over the winter and if frost heaving has occurred, mound soil or mulch around the plant crowns and exposed roots.

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