Released March 19, 2009
MANHATTAN, Kan. – Often the best time to divide overcrowded perennial plantings in the central and south-central United States is as soon as they emerge in spring and the soil gets dry enough to work.
“One of the most important factors in ensuring the success of new divisions here is to give them plenty of time to settle in before hot weather hits,” said Ward Upham, horticulturist with Kansas State University Research and Extension. “In that case, they’ll often go ahead and bloom during the same year.”
Peonies and irises are the traditional exceptions. They prefer late summer or early fall divisions.
Three ways to know when perennials need to be divided, Upham said, are:
1. The plant’s outgrown its allotted space.
2. The plant isn’t flowering as well as it used to.
3. It has developed a doughnut look -- dead in the middle with new growth on the edges.
With most perennials, gardeners can divide by either lifting the plant from the ground, or slicing off “starts” while the plant remains in the ground. In either case, saving as much of the root system as possible is important, Upham said. Gardeners can divide a lifted plant by removing excess soil and then either breaking it apart by hand or spading it into divisions, each of which has three to five growing points or shoots.
“You’ll also find no better time than early spring to improve your soil with compost, composted manure, peat moss, shredded leaves, dried grass clippings or some mixture of organic materials," he said.
How to add such organics depends on whether the site still contains plants.
“The best approach with new flowerbeds, total renovations and new planting holes is to roughly till in your amendments when soil is no more than moist,” Upham said. “For existing flowerbeds, just cover the area with 3 inches of organic material – which also will serve as this year’s mulch. Time will work the improvements into the soil.”
He recommends that gardeners who plan on a combination of approaches start by mixing their organic materials together in a wheelbarrow, tub or child swimming pool before incorporating or spreading them out.
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http://www.oznet.ksu.edu/News/story/briefs031909.aspx
Contact: Elaine Edwards, elainee@ksu.edu
