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How to Maintain Knock Out Roses

By Laura Reynolds ; Updated September 21, 2017

Every flower has its fan club but the rose is welcome in any garden. From the rugged rugosa to the refined hybrid teas of the last century, each rose has its place. The Knock Out roses originated by Wisconsin rosarian William Radler may be the easiest to maintain. Radler’s rose, marketed by the Conad & Pyle Co., is hardy through most of the U.S. and blooms throughout the summer. Its undemanding habit and disease resistance have made it one of today’s most popular landscape roses.

Let Knock Outs establish themselves their first season. Water them so they get an inch of water a week (including rain) and cut flowers as desired. Mulch their roots with a summer mulch of equal parts soil and compost, leaves, manure or peat moss. Don't fertilize until the first blossoms appear.

Remove summer mulch in the fall and put the same depth on for winter after the ground has frozen. In areas with severe winters, mound Knock Outs; pile mulch and soil a third of the way up the plant in December after the rodents have found other places to overwinter.

Fertilize Knock Outs with regular slow-release rose food according to the directions on the package. Fertilize as the first blooms appear; the shrubs will bloom for five to six weeks, then rest before a second period of bloom.

Cut flowers for your home but, beyond some trimming to keep them shapely, Knock Out roses require no special pruning or deadheading. Removing spent blooms does, however, encourage a denser bloom.

Keep a Knock Out rose tidy by shearing it to one-half to one-third of its height after the last hard frost in the spring. Remove dead wood in late winter or early spring. Rejuvenate your Knock Out rose periodically when it becomes leggy or bloom becomes thin. Cut the canes back to a foot to 18 inches high in early spring.

 

Things You Will Need

  • Hand pruning shears
  • Loppers or hedge shears
  • Garden spade
  • Summer and winter mulch materials
  • Water and bleach or rubbing alcohol

Tips

  • Do not over-fertilize or fuss over these plants. They need lots of sun and regular watering but they were bred by a man whose goal was to create a rose that almost anyone could grow. The result, first marketed in 2000, has proven to come very near his goal.
  • Plant Knock Outs in the same manner as other roses---dig a hole twice as large as the root ball, line it with amended soil (equal parts garden soil and compost or manure) and set the rose in, watering well daily for a few weeks. In USDA growing zones 6 and up, they are set with their bud unions an inch or two above ground but in zone 5 and north, the graft should be set an inch below the surface.
  • When planting bareroot roses, mound mulch about a third of the way up the canes until new shoots begin to grow through the mulch. Then remove the mulch and replace with summer mulch.
  • Mulch roses in the summer to shade roots and retain moisture. Mulch them with fresh mulch in winter to guard roots against dehydration by cold winds and the freeze-thaw extremes of sunny days and frigid nights.
  • Clean tools and blades between uses with a solution of water and 50 percent bleach or 70 percent rubbing alcohol to kill any bacteria that might be carried from plant to plant in the garden.

Warnings

  • Although these roses are remarkable, they still need at least eight hours of sun a day to bloom well. Plant them in a sunny, open place in your yard and allow plenty of space between them. They will easily grow to 4 feet tall and 4 feet wide.
  • Mulch the roots---not the rose bush. Keep mulch a few inches away from the main stem to keep plant tissues in open air. Like any rose, Knock Outs will develop fungal infections if stifled by poor air circulation.

About the Author

 

An avid perennial gardener and old house owner, Laura Reynolds has had careers in teaching and juvenile justice. A retired municipal judgem Reynolds holds a degree in communications from Northern Illinois University. Her six children and stepchildren served as subjects of editorials during her tenure as a local newspaper editor.