Terry L. Yockey
Dividing perennials maintains their vigor as well as being the easiest method of propagation. When a plant isn't blooming as well as it has in past years, it is usually ready to be divided. Many people hesitate to dig up a mature plant, but generally they benefit from being lifted and divided.
When you notice that new growth is just starting in the spring, it is time to divide here in the north. You can try division in early fall, but the success rate isn't nearly as high as with spring division.
Never divide your perennials on hot, sunny days. Wait till two or three days of light rain are forecast. The new divisions will have some time to rest and get soaked in after their move. Most plants will still look a little peaked when they are first replanted. Make sure they are well watered and they will soon recover.
Water the plants to be divided thoroughly a day before you plan to divide them Lift the clump with a fork or spade and then tease the roots apart with your fingers. Make sure each piece has its own root system.
Woody plants are a little harder to separate. After you lift them, wash the crowns to reveal the growth buds. Cut through the crown with a sharp knife leaving at least one healthy bud and root, then discard the woody center growth. For particularly large and densely rooted clumps, use two pitchforks back to back. Put them in the center of the clump and them pry the pieces apart. Sometimes with really tough perennials, you may have to go to even stronger measures. Place one foot on the side of the clump to steady it, and then stick a crowbar in the clump and lever out portions for replanting.
Keep a pail of water nearby to soak any divisions that have lost the soil around the roots. Use your pruners to trim all broken and straggly looking roots. This will stimulate the fibrous feeder roots to grow. Plants with large amounts of foliage may also need to have some leaves pruned after they are divided since there are fewer roots to sustain the large leaf system.
Prepare the area that you plan to put your new divisions in, before you lift the parent plant. If you are unable to replant right away, put the smaller divisions in a pot in a shady spot.
Remove any weeds and dead leaves from the new plants, before you replant them. These harbor diseases and are hiding places for slugs and insects.
Replant coral bells, peonies and iris slightly below soil level. All other perennials should be planted at the level they were growing before.
Iris should be treated somewhat differently when they need to be divided. Instead of lifting in the spring, wait till they have just finished blooming. Cut all the young rhizomes away from the older, spongy pieces. Trim the leaves to a fan about one-third of their original height. Replant the young rhizomes in a sunny place, amended with a large quantity of compost and other organic matter.
Some plants really resent being divided and it should be avoided if at all possible. These include asclepias (butterfly weed), euphorbia, gypsohila (baby's breath), oriental poppies, and columbine. Peonies can be divided, but be very careful of the fleshy tubers.
And remember, one of our obligations as gardeners is to share those left-over divisions with others. My grandma gave me a wonderful assortment of her "extras" when I first started gardening. She's gone now, but I still see her every spring as each of her favorites come into bloom.
"The Well Tended Perennial Garden: Planting and Pruning Techniques by Tracy DiSabato-Aust. Hardcover - 383 pages (August 15 2006) Timber Press.
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