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University of Illinois

Divide and Conquer: Preparing Spring Plants

FOR IMMEDIATE RELEASE
April 1, 2014

URBANA, Ill. - Spring is here and we are starting to get the gardening itch, said a University of Illinois Extension horticulture educator.

"Warm days tease us and blooming crocus encourages us," said Martha Smith. "But we know Mother Nature is still in charge and she can release her fury at any time. Now is the time to start thinking about what will need to be divided in our gardens.

"In general, most perennials need to be divided every three to five years. The ideal time is in the spring just as active growth starts. It is at this time you can do the least amount of irreparable damage. All systems are go! The plants are coming out of their dormancy and are primed for growing," she said.

Some may argue that there are specific plants that respond to dividing better at later times during the growing season. "Yes, that is true. The recommended time for oriental poppy, peony, and Siberian iris is late July or early August, but spring is still okay if that is the only time you can divide," Smith said.

Divide early spring bloomers after bloom and they will have all season to anchor new roots and set buds for next spring. Divide summer-fall bloomers in spring and they too will be able to set roots and respond to daylight and temperatures to bud and flower. For the majority of perennials in the garden spring is a great time for dividing

Usually a plant will show signs of needing division. They become overgrown with dead, unsightly centers, or their vigorous growth has sent them to places in your garden where they are not welcome! Plants often have fewer or smaller flowers and are in overall poor health due to the plant depleting the fertility of the soil as it crowds itself.

"Let the plant be the gauge and not a calendar," Smith said. "Some perennials may need dividing every two years while others may not need any attention for seven years."

To divide mature clumps of perennials, lift the clump and separate the outer active growing portion from the center. Discard the center and replant the active growth areas. Be careful not to over-divide. Leave a proportionate amount of roots to crown. Too few roots will not be able to support a large crown. Too small a crown will not give you much of a visual display. Too large a clump may mean you'll be dividing this plant again soon.

"Don't worry about being rough," she said. "Some perennials need a backhoe and a pickaxe! After lifting these brutes, use a saw or a sharp flat-edged shovel. On the softer side, some perennials lift very easily and you can actually separate them with your hands."

Replant the portion you are keeping and discard or give away the rest. Prepare the planting area by adding compost or aged manure. Remember, a perennial can be expected to live in that spot for several years so take a few minutes and amend the planting area. You will be glad you did.

"You should stagger your plant divisions so that the whole garden will not need dividing at the same time," she said. "A good three-to four-year-rotation plan will yield a nice display of flowers each year. "

Source: Martha A. Smith, Extension Educator, Horticulture, smithma@illinois.edu

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