How to Prune Shrub Roses and Knock Out Roses

Knock Out Rose

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Among the family of landscape roses, the shrub roses occupy a unique role apart from the more temperamental hybrid tea roses, floribundas, and grandifloras. As a class, shrub roses tend to be less showy plants with a growth habit that often resembles the wild parent species. More often than not, there is one main flower production period during the growing year, sometimes with a second smaller flush of blooms in the early fall. But while their flowers are less dramatic, shrub roses make up for this by being extremely hardy and far easier to care for than the sensitive teas and other hybrids. With shrub roses, pruning tends to be a much easier process than with hybrid roses, although the exact methods for pruning depend on what type of shrub rose you are dealing with.

Types of Shrub Roses

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

Larger upright shrub roses, including some considered ramblers, are often used to make large, bold statements in a garden, due to both their blooms and sprawling growth habit. Similar to upright shrub roses are old-fashioned roses of the type that were popular before the rise of the hybrid tea rose. Since these old-fashioned roses require much the same type of care as shrub roses, they are often considered together with the shrub roses in discussions about pruning. Large shrub rose bushes are somewhat wild and ill-behaved when compared to the narrow upright hybrid tea roses, or even to the low mounding habit of the floribundas (although floribundas must be taught their obedience through pruning). Many shrub roses also bloom only once a year instead of the “from summer to frost” period of many popular modern roses.

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

While there are some general rules for pruning both the upright and low-growing types of shrub roses, there are also specific tips for pruning specific types.

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

When to Prune Shrub Roses

While on-going deadheading of spent flowers should be done constantly, the major pruning of shrub roses to shape the plants should be done in spring. Some types require fairly light pruning, others thrive on more vigorous pruning, but in all cases, spring is the time to perform this task.

General Pruning Tips for All Shrub Roses

If you do nothing else, two rules of thumb will let any shrub rose thrive fairly well:

  • Deadhead them. Whether your shrub rose blooms once a year over a short period in late spring or early summer or blooms repeatedly, it will likely benefit from deadheading, which will promote a longer bloom period and may even prompt a second bloom period. A few types, like the Knock Outs, do self-deadhead, dropping their spent flowers automatically. Roses that never produce hips, or that produce tiny or mangled hips, do not need to be dead-headed to increase blooms. Late in the blooming season, you may want to stop deadheading and let the hips ripen for an autumn show or to provide food for birds.
  • Allow large shrubs to remain large. Many shrub roses bloom on shoots emerging from old wood, so you cannot cut back old wood in spring without sacrificing blooms. When these plants need to be tamed, do it little-by-little—trim out just a few entire canes in spring, then perform whatever minimal pruning is needed to maintain some shape and tidiness, both in-season and during the dormancy period. However, don’t expect a large shrub rose to ever look completely tidy.

    Project Metrics

    • Working Time: About 20 minutes per rose bush
    • Material Cost: None, unless you need to invest in pruners

    What You'll Need

    Equipment/Tools

    • Sturdy work gloves and a long-sleeved shirt
    • Bypass pruners

    Instructions

    Lee Reich, Author of "The Pruning Book," breaks shrub roses and old-fashioned roses down into three classes based on how vigorously they grow. If your rose happens to closely fit one of the types described, you are in luck. If your rose doesn't exactly match one these types, then match yours to whatever description comes closest.

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

    Although they are less temperamental than hybrid roses, 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 healthy white wood. Make your cuts at a 45-degree angle, about 1/4 inch above a bud. The goal of pruning should be first to remove all dead or broken canes, and secondly to create a pleasing shape that opens up the interior of the shrub to light and air.

    How to Prune Group 1 Shrub Roses

    Group 1 shrub roses include those that few new shoots, and which produce their flowers on old stems. Examples include Gallica roses, Father Hugo’s rose, musk rose, and Scotch or Burnet roses. Prune these lightly in spring.

    How to Prune Group 2 Shrub Roses

    This group includes shrub roses that produce many new shoots emerging from the ground, and produce their flowers mostly on old wood. Examples include Burgundy rose, cabbage (centifolia) rose, Rosa x alba, Damask rose, rugosa rose, and once-blooming modern shrub roses. For this group, in spring, cut out the oldest one-third the canes, and reduce the length of any remaining long or droopy canes that are too long and droopy.

    How to Prune Group 3 Shrub Roses

    Group 3 shrub roses include roses that produce many new shoots from the ground, but which produce flowers on both old and new stems. China rose, and continuous-blooming modern shrub roses—the Knock Out family—fits here. For these, prune down the canes hard, near to ground level, each spring.

    Pruning Tip

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

    Illustration of how to prune knock-out roses
    Colleen Tighe / The Spruce, 2019

    Tips for Pruning Knock Out Roses

    The Knock Out group of shrub roses occupies a special niche that incorporates some of the features usually found in hybrid roses. Introduced in 2000 by Wisconsin breeder William Radner, the Knock Out roses bloom repeatedly every 5 to 6 weeks through 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 are renowned for being more resistant to diseases than most roses.

    The 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 one-third of the desired final size. Knock Out roses typically triple in size after pruning.
    • Don't deadhead. Knock Out roses are said to "self-clean," and deadheading really does nothing to improve blooming.
    • Remove dead or damaged wood when you see it.
    • Every two or three years, remove one-third of old growth to rejuvenate the shrub.