Kansas

Gardeners with winter-damaged deciduous shrubs need to remember correct pruning uses just three basic methods: thinning, heading back and rejuvenating.

"The approach you choose should depend on the type of shrub, as well as the extent of its damage," said Ward Upham, Kansas State University Extension horticulturist. "But be warned that now is not the ideal time to prune all flowering shrubs. You may affect the amount of blooms you get this year."

Normally, Upham recommends pruning the shrubs that flower in spring just as soon as they've finished flowering. This includes forsythia, lilac, Vanhoutte spirea and flowering quince.

"Shrubs that bloom on the current year's growth-such as Rose-of-Sharon, Bumald spirea and Japanese spirea-do best if pruned in late winter or early spring," he said. "That's also true of shrubs that don't flower. But slowly emerging winter damage can force you to change that timetable."

The thinning approach to pruning may be all some shrubs need this spring. Its typical purpose is to open up a shrub that has grown too dense.

"You remove most of the inward-growing twigs. Either cut them back to a larger branch or cut them back to just above an outward-facing bud. Or, with a multi-stemmed shrub, simply remove old or damaged canes," Upham said.

Heading back is pruning to reduce height or keep a shrub compact.

"You cut back to a bud, in order to remove the end of a branch. This could be the best method for shrubs with tip damage," he explained. "The trick is not to cut the branches at a uniform height. This creates a 'witches-broom' effect."

Rejuvenation is the most severe pruning, so normally is done when shrubs are dormant.

"Don't try it with anything that does not have the kind of multiple stems you see on shrub roses, spirea, forsythia, pyracantha, ninebark, Russian almond, little leaf mock orange and flowering quince," Upham warned. "But if a multi-stemmed shrub becomes too big, sustains severe damage, or simply has too many old branches to justify saving the younger canes, you can cut all the stems back to 3- to 5-inch stubs. Soon, your shrub will again be a younger-looking version of itself ."

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