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Perennials: Divide and Conquer | Fall 2004 Out Here Magazine

Splitting the roots of a perennial before replanting - Tractor Supply Co.
Smaller perennials can be pried apart by hand; others may require a knife or pruning clippers.

By Peter V. Fossel

Photography by Donnie Beauchamp

Neighbors who see me dig up a plant and whack it apart with an ax think I'm crazy until I explain that it's a perennial; it needs a root division to bloom better; and I end up with more plants, to boot.

Gardening books say to divide herbaceous perennials every three to five years, but I have a different system. I divide roots (1) when I have time, (2) when the plant is not blooming properly, or (3) when I want more plants.

Chrysanthemums and asters may need dividing every two years, so they won't grow into non-flowering clumps of leaves and roots, but others, such as bleeding hearts and peonies, may never need to be divided.

Fall is the time to divide spring- and summer-flowering plants, but be sure the plants have four to six weeks before ground freeze to re-establish themselves.

Water the plant a day or two in advance, and avoid separating roots on a hot, sunny day when they easily can dry out.

Certain perennials resent being divided. The list includes butterfly weed, euphorbias, Oriental poppies, baby's breath, Japanese anemones, and columbines. Some say the list includes peonies, but I've had good luck dividing these. With most other perennials, root division is a wonderfully inexpensive way to increase your plant stock from your own garden, or from those of friends and neighbors.

The job itself is straightforward. Simply dig up the plant with a root ball 12 to 24 inches wide to ensure you won't be cutting off valuable roots. Pry it out of the ground with your spade and shake off loose dirt and leaves.

Smaller, clumping plants, such as lamb's ear, can be pried apart by hand. Others may need a knife or pruning clippers. Larger, tougher root balls — red hot poker and ornamental grasses, for example — can be divided with a shovel, a hand saw, or ax.

Try hosing down the roots first to make them easier to work with. Another method that works well with large, spreading root systems is to push two garden forks into the mass and pry the root system apart.

The number of divisions is a matter of preference; just be sure each has a section of woody roots and a growth point or bud. Keep these damp until they are replanted.

Rhizomes and tubers require a little more finesse in dividing. Rhizomes, such as bearded iris, are thick, fleshy stems that grow at ground level. Cut these with a sharp knife to get a few inches of rhizome and one fan of leaves on each section, pruned back half way.

Tuberous roots, such as those of dahlias, also are cut with a knife and need a piece of root and growth bud on each piece.

Certain perennials resent being divided. The list includes butterfly weed, euphorbias, Oriental poppies, baby's breath, Japanese anemones, and columbines. Some say the list includes peonies, but I've had good luck dividing these.

With most other perennials, root division is a wonderfully inexpensive way to increase your plant stock from your own garden, or from those of friends and neighbors.

Peter V. Fossel is a writer and organic farmer in Goodlettsville, TN.