Can You Use Hedge Trimmers to Trim Knockout Roses?

About Knock Out Roses

• Knock Out roses were introduced in 2000 in their original red-pink, with open blossoms of only seven to 11 petals each and dark reddish-green foliage. The Knock Out family has grown to include varieties with doubled flowers, and those that bloom in pale pink, medium pink, pink with yellow centers and yellow. All Knock Out roses are bred for disease resistance and to be self-cleaning, meaning petals fall off spent flower heads, and to bloom on a five- to six-week cycle from spring until stopped by a hard frost.

When to Prune Knock Outs

• As with other roses, late winter to early spring is the time to prune a Knock Out rose. Use swelling buds on the canes of the plant as a guide; as they begin to send up shoots, it's time to prune. Hold off on pruning a newly planted or young Knock Out to avoid stressing the plant. Wait to prune until at least its second season in your garden before pruning your Knock Out rose with any pruning implement. Once the plant has achieved its mature size of 4 feet tall and wide, you can take up your trimmers the following spring.

Hedging Knock Outs

• When buds are swelling on your mature Knock Out, it's time to take back some of that growth to reinvigorate the plant for plenty of fresh blooms. While the grower gives 3 to 4 feet as the ultimate height of the plant, it is widely reported to reach up to 6 or 7 feet when left unpruned. Conrad-Pyle recommends taking the plant back to 12 inches tall all over each spring, expecting it to triple in height. Depending on the ultimate height you want the plant to attain, you can leave it taller. Keep in mind that the plant puts on at least 2 feet of growth over the season. Shape the plant to encourage allover growth as you shear, aiming for a profile that is wider at the bottom than the top of the plant and domed at the center. This way, all parts of the plant get sun and the bottom of your Knock Out doesn't become leafless and leggy.

Considerations

• For the healthiest, most productive plant, get out your loppers or bypass pruners after you shear to open up the center of the bush to more light and air. Prune selectively, removing a few of the largest canes at their bases. Remove any dead or the rare diseased cane anytime you notice them -- cleaning your pruning tool with antiseptic cleaner between cuts. Rake away all dropped foliage to prevent fungal disease. Even though Knock Outs are resistant to black spot, it is better not to tempt the gardening gods with sloppy maintenance. A second shearing -- taking the plant back by one-third -- can be helpful after the first flush of bloom to control the size of your Knock Out.