Pruning Knockout Roses
How to Prune Knockout Roses
Knockout roses are a relatively low-fuss variety that can make a welcome addition to any yard or garden, but they do require a little seasonal pruning in order to grow healthy and beautiful. Cut back your roses extensively at the beginning of spring, and shape them up as needed throughout the rest of the year. Give them one final light pruning before they go into dormancy and they’ll be ready to return full force the next year.
Pruning Roses Correctly
Grab a pair of sharp bypass pruners.Bypass pruners cut like scissors, making them preferable to anvil-type pruners, which have a tendency to crush the stems as they cut. Nice, clean cuts are essential to maintaining the health of the plant.
- If you don’t have a pair of pruners handy, you could also use full-sized hedge clippers or trimmers. Whatever tool you use should be nice and sharp and able to make clean cuts.
- When you need to cut canes larger than about inch (1.3 cm) in diameter, switch to a set of larger loppers.
- Disinfect pruners with rubbing alcohol or bleach diluted with water to sterilize them.
Wear gloves to protect your hands and arms.In order to prune your knockout roses safely and effectively, you’ll need to pull on a pair of rugged elbow-length gardening gloves. Your gloves should be thick enough to safeguard your skin from any thorns growing on the bushes.
- Don’t attempt to prune your knockout roses without some kind of protective covering—a pair of standard wrist-length gardening gloves is better than nothing.
Disinfect your pruners before you get started.While you’re pruning your roses, stop periodically to dip them into a container filled with cleaning solution. Any all-purpose household cleaner will do the trick. Making sure your cutting blades are properly sanitized lowers your chances of accidentally spreading disease from one plant to another.
- Get in the habit of disinfecting your pruners regularly, whether you’re trimming a little or a lot.
- Alternatively, you can use a solution made up of 70% rubbing alcohol diluted in water.
Cut the canes at a 45-degree angle.Make your cuts roughly inch (0.64 cm) above an outward facing bud, with the slant pointing away from the bud. This helps promote new growths to grow outward rather than inward. This technique should be used regardless of the time of year or size of the growth you’re pruning.
- Angled cuts help water run off the stem and reduces the chance of fungal rot.
- Cutting too close to the bud could shock it, while cutting too far away might leave too much old growth behind, forcing the plant to direct valuable resources to canes that are no longer able to produce new buds.
Performing Major Pruning in Early Spring
Wait until the second or third season of growth to cut back your roses.By holding off until your roses have neared their full size, you can ensure that they’ll be able to withstand having whole sections removed. A mature knockout rose should be about 4 feet (1.2 m) tall by 4 feet (1.2 m) wide before you begin hacking at it.
- A fully-grown knockout rose will require the most pruning around mid-February to early March. Young roses, by contrast, only need to be touched up throughout the growing period to remove dead or dying growth.
- Knockout roses can often go as long as 2-3 years between major prunings, depending on how rapidly they grow and how big or small you like to keep your plant.
Prune your roses as soon as the buds break dormancy.Look for small buds to begin forming along the stems of the plant. If the existing buds have swelled up but no new growth has appeared, it means the roses are ready to prune.
- The main pruning period for knockout roses is in late winter or early spring, just as the plant prepares for another season of growth.
- You can still prune your roses even if new growth has already begun. Buds might start forming early if the winter was especially mild. In this case, snip the growth back to the first dormant bud.
Start by cutting away overlapping canes.Clip one or both canes as needed to get the plant’s interior structure growing straight and vertical. Creating some separation between the canes prevents them from rubbing against one other, making the plant look neater and promoting stronger, more lasting growth.
- By reducing the density of your rose bushes early in the season, you can make sure they continue putting out neat, attractive growth all year long.
- Thinning out overlapping canes and stems also promotes better air circulation through your rose bushes, making them less vulnerable to fungal diseases.
Remove one-third to one-half of the plant’s overall size.You can cut healthy shoots back considerably without worrying about harming the plant. Doing so will prevent your roses from putting too much energy into maintaining an overabundance of foliage. As a result, it will produce more flowers.
- Keep in mind that your knockout roses will grow vigorously after being pruned. As a general rule, you’ll want to cut them 1–2 feet (0.30–0.61 m) shorter than you would ultimately like them to end up.
- Be careful not to get too overzealous with your pruning. Trimming more than half of the healthy, mature canes could cause the plant to struggle to regrow lost foliage, stunting its growth.
Trim your bushes to the desired height and width.Maintain the appearance of your knockout roses by giving them a gently rounded, dome-like shape. Be sure to snip any stems or offshoots that extend far enough beyond the foliage on the outer edges of the bush to stand out.
- To improve air circulation and control the spread of diseases in warmer weather, try trimming your bushes into a rough ‘V’ shape, leaving them open in the middle.
Maintaining Your Roses During Late Spring and Summer
Do some corrective pruning throughout the peak growing season.Shaping up your rose bushes sporadically as they fill out will encourage them to put more of their resources toward producing beautiful new buds. With a little attention here and there, you’ll begin to see more dramatic flower production by the time the days start getting shorter.
- Avoid heavy prunings during the heat of the summer. Your roses will already be somewhat stressed due to the heat, so losing too much healthy growth only weakens them further.
Remove damaged and diseased wood.Any sections of the plant showing signs of disease should be dealt with immediately to prevent the condition from spreading. Similarly, old, brittle wood invites harmful pests, fungi, and bacteria to attack the plant, and should also be cut back as soon as possible.
- Throughout the growing season, the primary purpose of pruning is to keep your roses healthy and active. This can be achieved by removing any unhealthy-looking parts of the plant that could become an issue if left alone.
Deadhead dead and dying blooms to extend the bloom season.Deadheading is the practice of snipping off spent or failing flowers in order to make room for new ones. Snip the stem down to first group of five leaflets below the flower cluster. In a few short weeks, another round of blooms will appear in their place.
- In most cases, you’ll be making your cuts approximately 6–8 inches (15–20 cm) below the flowers themselves.
- During extreme heat, only cut back to the first set of leaves rather than going further down the stem.
- Deadheading is essential for improving both the health and aesthetic quality of your knockout roses.
Aim for a uniform appearance.If a few fast-growing shoots exceed the length of the surrounding shoots, trim the longer sections to restore the plant to an even length. Repeat this process on all visible sides of the bush. Otherwise, it can quickly overtake its surroundings and begin looking unruly.
- In addition to vertical growth, new growth will also expand outward and below the plant in the spring and summer. This "leggy" undergrowth should also be kept short.
Trimming Your Roses Before Winter
Prune 1 final time if desired before the first frost of the year.Ideally, you should aim to have your pruning done by the end of summer or the first couple weeks of fall, when the weather is still warm. Once it gets cold, new growth will begin to taper off as the plant prepares to enter dormancy.
- Stop pruning your knockout roses in early fall at the latest. Any new growth they put out after this time may not harden off in time for winter.
- Your roses will benefit from getting a little rest before the next growing season.
Clear away dead wood.Just like you did in the summer, inspect your knockout roses carefully once more to identify and cull weak, sick, or dying canes. Otherwise, disease could spread throughout the bush unchecked, kill it off completely by the time winter sets in.
- At this point, it’s advisable to remove as little of the plant’s overall size as necessary.
- Avoid disturbing younger canes. You don’t want to accidentally stimulate new growth that will just die off and weaken the plant.
Reduce the overall height of your rose bushes.Just before your roses retire for the season, you can trim up to one-third off their total height. Focus on excess growth that doesn’t contribute to the general shape of the bush. If there are any long, non-flowering stems sticking out from the top or sides, be sure to see to these as well.
- If your roses just barely managed to reach their ideal height during the peak growing season, a little light corrective pruning will be best.
- Fall pruning is not a major ordeal, and many gardeners even choose to skip it altogether.
QuestionWhy are my knockout rose bushes just skinny and spindly now after blooming for about 6 years?
HorticulturistHorticulturistExpert AnswerPrune your rose bush to about 6”-8” above the ground. This is called a rejuvenation prune and will encourage bushier growth.Thanks!
QuestionHow can I prune my roses to a 3-foot height?
HorticulturistHorticulturistExpert AnswerPrune them in the spring before the leaves appear. Prune to the desired height. Prune above an outward facing bud and make a 45° angle cut.Thanks!
QuestionI recently planted new knock out rose bushes and they are drooping. The rose buds seem too heavy when wet and the stems are long so they bend and the bud are on the ground. Planted them last week. What should I do?wikiHow Staff EditorStaff AnswerIt sounds like there's an overabundance of growth on the bush. Try clipping a few of the flower clusters 6-8 inches below the blooms to alleviate some of the weight. Keep in mind that it's okay to remove as much as one-third to one-half of the plant's overall volume as long as you do it early enough in the spring for it to grow back.Thanks!
QuestionOur roses bloom several times all year long in Texas, but our bushes are not nice and thick. Should I prune them?wikiHow Staff EditorStaff AnswerIf your rose bushes haven't yet filled out and become lush, there's probably no need to prune them. However, you might do a little maintenance by removing overlapping or tightly-cluster canes and taking off a portion of the plant's overall height to keep it under control.Thanks!
QuestionMy roses were trimmed too late in the spring and only bloomed once. I want to cut them back now due to their weight and what looks like an insect problem. How should I do that?wikiHow ContributorCommunity AnswerLeave three main branches about twelve inches tall. You'll be surprised how much regrowth and blooms you get.Thanks!
QuestionCan a knocker rose bush be transplanted to another location?wikiHow ContributorCommunity AnswerYes, it can.Thanks!
QuestionIf my knockout roses quit blooming and have white spots on the leaves after I pruned heavy, will they survive?wikiHow ContributorCommunity AnswerThe white spots are either fungal or mites. Find your local gardening place and buy a good spray to help ensure survival; taking a small sample with you helps. Also, don't prune too heavily in the growing season.Thanks!
QuestionShould old, dead roses be cut off?wikiHow ContributorCommunity AnswerYeah. It can hurt the rest of the rose, and it's useless and ugly.Thanks!
QuestionHow do I know when to prune my bushes?wikiHow ContributorCommunity AnswerStart pruning if the leaves are getting green or are too long for you.Thanks!
QuestionMy rose is in a pot. Can it be planted in flower bed now?wikiHow ContributorCommunity AnswerYes. I always use Quick Start and water the plant before I move it, then water with Quick Start for three days after planting. In my experience, the rose has no shock using this method.Thanks!
Why do they only bloom on the top?
How low can I cut knockout roses in Houston?
Should I cut the old wood of the roses down if a lot of new growth is starting at ground level?
Knock Out roses start out with big blooms as the summer begins, but as it wears on the blooms get smaller and smaller - what is the cause of that? What can I do?
Can I trim my rose bushes if they weren't trimmed in early spring and are developing new roses and buds?
- Knockout roses can triple in size during their peak growing season. Keep this in mind when deciding on a preferred height and shape for your bushes.
- Rather than simply discarding clipped canes that boast attractive flowers, stick them in a vase and put them on display in your home.
- Have a wheelbarrow on standby to haul off your clippings when you’re done.
Things You'll Need
Hedge clippers, trimmers, or loppers (optional)
Elbow-length gardening gloves
Cleaning solution (for disinfecting pruners)
Sources and Citations
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of How to Prune Knockout Roses was reviewed by on May 11, 2019.
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