How to Prune Shrub Roses and Knock Out Roses

pink Knock Out roses

Garden Photo World/Getty Images

Overview
  • Total Time: 30 mins
  • Skill Level: Intermediate
  • Estimated Cost: $0

Among the family of landscape roses, shrub roses tend to be less showy plants with a growth habit that often resembles the wild parent species. There often is one main flowering period during the growing season, sometimes with a second smaller flush of blooms in early fall. Shrub roses make up for their less dramatic flowers by being extremely hardy and easier to care for than the sensitive tea roses and other hybrids. With shrub roses, pruning tends to be a simple process, though the exact methods for pruning depend on the type of shrub rose you are dealing with.

Tip

Use sharp bypass pruners rather than anvil pruners. Bypass pruners cleanly sever the stems rather than crush them. Crushing can create an entry point for insects and diseases. Make sure your pruners are clean, disinfecting them before and after each use.

What You'll Need

Equipment / Tools

  • Sturdy work gloves and protective clothing
  • Bypass pruners

Materials

  • Rose bush

Instructions

Many experts divide shrub roses into three groups based on how vigorously they grow. If your rose doesn't exactly match one these groups, then select whichever description comes closest.

  • A rose that blooms mostly from old structure is in Group 1.
  • Roses that produce some blooms from new wood but mostly from old wood are in Group 2.
  • Roses that put up a lot of new growth from the ground and bloom on both old and new wood are in Group 3.

Shrub roses should always be pruned by cutting stems back to a healthy bud. After you cut, look for healthy white wood in the cut. If it is brown, continue to cut until you reach white wood. Make your cuts at a 45-degree angle, about 1/4 inch above a bud. The goal is to remove all dead or broken canes (stems) and to create a pleasing shape that opens the shrub interior to light and air.

  1. Prune Group 1 Shrub Roses

    Group 1 shrub roses include include Gallica roses, Father Hugo roses, musk roses, and Scotch or Burnet roses. Prune these lightly in the spring, getting rid of diseased or dead wood.

  2. Prune Group 2 Shrub Roses

    This group includes the Burgundy rose, cabbage (centifolia) rose, Rosa x alba, damask rose, rugosa rose, and once-blooming modern shrub roses. In the spring, remove the oldest third of the canes, and reduce the length of any remaining long or droopy canes to create a pleasing shape.

  3. Prune Group 3 Shrub Roses

    Group 3 includes China roses and continuous-blooming modern shrub roses, such as the Knock Out rose family. For these roses, heavily prune the canes nearly to ground level each spring.

Red Rambler Roses (Rosa) on a grid at a house wall
Annette Hempfling/Getty Images

Types of Shrub Roses

There are many ways to categorize shrub roses. But the most basic distinction is between those with an upright, bushy habit and those that are low-growing.

Upright shrub roses are often used to make bold statements in a garden due to their blooms and sprawling growth habit. However, these large shrub roses can be somewhat wild and ill-behaved in their growth and must be tamed through pruning that focuses on shaping them. Many of these shrub roses only bloom once a year instead of the “from summer to frost” period of many popular modern roses.

Other shrub roses demonstrate a low-growing habit that hugs the ground. This type includes a special class of selectively bred plants known as Knock Out roses. All of these low-growers are often used as ground covers in sunny areas because of their toughness and hands-off maintenance requirements.

When to Prune Shrub Roses

Deadheading, or the removal of spent flowers, should be done constantly throughout the growing season. However, the majority of shrub rose pruning to shape the plant should occur in the spring. But you can remove any broken or diseased portions as soon as you spot them.

Tips for Pruning Shrub Roses

Two rules of thumb will let any shrub rose thrive fairly well:

  • Deadhead the flowers. Whether your shrub rose blooms once a year in late spring or early summer or it blooms repeatedly, it will likely benefit from deadheading. This can promote a longer bloom period and might even prompt a second bloom. A few types, such as the Knock Outs, drop their spent flowers automatically and don't require deadheading. Also, late in the blooming season, you might want to stop deadheading and let the hips ripen for an autumn display or to provide food for birds.
  • Allow large shrubs to remain large. Many shrub roses bloom on shoots emerging from old wood, so you can't cut back old wood in the spring without sacrificing blooms. When these plants need pruning, do so little by little. Trim out just a few canes in the spring. And then throughout the year, prune whatever is necessary to maintain the plant's shape. However, don’t expect a large shrub rose to ever look completely tidy.

Tips for Pruning Knock Out Roses

The Knock Out group of shrub roses blooms repeatedly every five to six weeks throughout the growing season. There are varieties with both single and double flowers. The plants typically grow no more than 3 or 4 feet tall with a similar spread, and they tend to be more resistant to diseases than most roses.

The general rules for pruning Knock Out roses include:

  • Always prune in early spring when new shoots are beginning to form on the canes.
  • Prune to about a third of the desired final size. Knock Out roses typically triple in size after pruning.
  • Remove dead or damaged wood when you see it.
  • Every two or three years, remove a third of old growth to rejuvenate the shrub.
Illustration of how to prune knock-out roses
Colleen Tighe/The Spruce, 2019