Pruning Knock Out Roses

Knock out roses are gaining popularity because they are easy to care for and fairly disease resistant. One of their selling points is that they are “self cleaning” meaning the petals fall clean, and while that may be true this article discusses why you should regularly deadhead them and explains the simple process of pruning Knock Out roses annually.

Deadheading Knock Out Roses.

During the growing season it’s worth your time getting rid of any spent flowers by deadheading the rose bush. Deadheading on a regular basis will help the plant maintain its compact bushy habit and encourage prolific flowering. It is promoted as “self cleaning”, however, lightly pruning knock out roses is beneficial to the plant. If you don’t remove the spent flowers, they will develop into rose hips and the energy the rose uses in forming these hips greatly reduces flower production.

If you like the look of the orange coloured hips on the rose as some do, then just realise that you wont get masses of flowers on your knock out rose. When deadheading you just cut the spent flowerhead back a couple of inches – nothing too severe during the growing season as the flowers bloom on new wood. This encourages new growth and an abundance of new flowers. You also want to trim any wayward branches to help keep its shape.

When to Prune Knockout Roses

Knockout roses benefit from an annual prune. For those living in a warmer climate zone, for example in zones 7+, you’ll want to prune knock out roses in mid to late Winter. For those living in colder climate zones, early to mid Spring once the frosts are over, is more ideal. Though you are always better off asking a local plant nursery, local garden club or rose society the ideal rose pruning time for your particular location, so you get the timing spot on.

Pruning Knockout Roses

Because the knock out rose is a landscape shrub rose, it doesn’t need the detailed pruning that some other species need. Remove any dead or damaged wood and if there is a lot of overcrowding of branches in the centre of the rose you can remove a few of these branches if you wish, to open the rose plant up a little and improve air circulation. This is not necessary however, and some people are happy to leave them as is. It won’t hurt the plant if you don’t.

Knockout Roses Pruning

You can easily prune knock out roses annually by reducing their height by half to two thirds. This way you will end up with a knockout rose that is around 12-18 inches high after pruning. You don’t need to fuss with each stem individually, cutting to an outward facing bud either; you can use hedge trimmers or loppers to prune the knock out roses down to size.

Some folk don’t prune down to 12 inches as they prefer to have taller knockout rose bushes so it’s up to you. You can afford to experiment a little with this plant so one year you might prune it 12 inches and see what height you end up with at the end of the growing season; the next annual prune, you could prune a little higher; 18 inches or more, and see how tall they grow from that pruning height.

There’s no hard and fast rule with this easycare rose, though knockout roses do benefit from an annual prune. After experimenting, you can just decide on the pruning height you prefer.

Every couple of years remove some of the older woodier branches at the base of the plant to encourage the development of new branches which will produce much better blooms. Doing this will keep your knock out rose blooming for many years. Pruning Knockout roses is an easy garden task and one more reason this rose is so popular with gardeners.

61 Comments so far

  1. Jean Wittrock on September 1st, 2011

    I have 3 knockout rosebushes. One is growing in a sunny location, it is growing tall, some of the stems are really thick an some are brown like there dead, but new growth and roses seem to flurrish, they really bad.

  2. admin on September 1st, 2011

    Hi Jean
    If the rest of the rose bush is growing well as you say with new growth just cut out the dead stems. Also have a good look at the plant to check for the presence of any pests or diseases that may have caused the dead stems in the first place. If present you may have to spray with a suitable pest or disease treatment.

  3. Joe Graves on September 26th, 2011

    I planted my first knockout roses this summer….I live in Tennessee….the plant appears very healthy and gets afternoon sun mostly….I have been “deadheading” it regularly…the blooms are beautiful….but it is starting to produce alot of red leaves that appear healthy as well….what causes this and what should I do about it if anything….thanks in advance!

  4. admin on September 27th, 2011

    Hi Joe
    as new leaves develop on roses they can appear reddish in color until they grow out and green up. This sounds to me like what is going on here as you say the “red” leaves are healthy. Enjoy your first season of knock out roses.

  5. Susie on September 28th, 2011

    I was not able to prune my knock out roses in late winter as recommended due to my husband being in the hospital off and on all summer. Now my knock outs are very tall and leggy. I really want to cut them back because I see a lot of stem at the bottom with no foliage. Is it ok to prune them even though it is late September?

  6. admin on October 5th, 2011

    If you live in the southern hemisphere and are in a warm climate you could still prune them now but I wouldn’t be too severe with it, maybe just reduce them by one third. If you live in the northern hemisphere it would be fall and it may be best to leave it if you are in a cold zone as they would be starting to slow down their growth as they approach dormancy. If in a warm zone though, I would still give it a shot, but again, I’d only prune a third off the plant.

  7. Joan on October 16th, 2011

    I planted a single double knock out rose this Spring. I live in Missouri. It has grown so huge that it’s overtaking my landscape. I want to cut it down so it goes more with the rest of the plants. Is it okay to cut it back now (Oct) or should I just wait until late Winter or early Spring and worry about managing it next year?

  8. admin on October 16th, 2011

    Hi Joan
    I’d be interested to know how “huge” your knock out rose has grown in your area and what you’ve been feeding it:) Missouri has a USDA climate zone ranging from 4 to 7, so I’d wait to cut it back until early spring after the last frosts. Prune it down to about a foot then and see how high it grows through summer. Pruning that low might keep it from growing too large. Knock out roses usually grow 3 to 4 foot in height and width but if this is too large for your landscape you may want to either replace it with a lower growing landscape rose or you could just give it a light prune every few weeks during the growing season. This will help to keep it to the size you want, but you’re only going to get a flush of flowers every few weeks if you choose to to this.

  9. rossana reese on October 24th, 2011

    Hi,

    I planted 4 (5 gal) double knockout rose plants this past July, and had enjoyed blooms since.

    (I did not know that it needs to be deadheaded or pruned. Just started gardening…)

    I have read different articles of ways to deadhead but I am not sure which way would give the best result, ie a couple of inches from the spent flowers or 4rth of an inch next to the first 5 leaf of a stem, etc.

    I also do not know if I should prune in the first year since I want to keep th current height(3ft), but if needed, not sure whether to prune now or wait mid to late winter (Feb?).(I live in Georgia)

  10. admin on October 24th, 2011

    Hi Rossana
    with these type of roses you don’t need to be overly concerned with how you deadhead them. A couple of inches from the spent flowers is fine, even 3 inches would be fine if you are trying to keep the plant at a particular height – you don’t have to be too particular. I would prune them in their first year though, as in your area knock out roses can grow quite tall, and you mention you want to keep them around the 3 foot mark.
    Prune them next February down to about 18 inches in height, and then see how tall they grow through the season. If they grow taller than the 3 foot you prefer, you might want to prune them down to 12 inches the next year you do the annual prune. The wholesalers of these roses reckon they will usually triple their pruning height during the growing season, but just experiment the first time with 18 inches seeing it’s the first yearly prune and if it gets too tall, prune down to 12 inches the next time around. With regular deadheading of the spent blooms during the growing season, you can usually keep them at around the 3 foot mark at any rate.

  11. Sandra on October 26th, 2011

    I live in middle Tennessee what month do I prune?

  12. admin on October 26th, 2011

    Hi Sandra
    March would be the time to prune in Tennessee, after the last hard frost.

  13. Joy on November 10th, 2011

    I am in Raleigh, NC when should I prune my Knock Out roses?

    Thanks
    Joy

  14. admin on November 10th, 2011

    Hi Joy
    the best time to prune your knock out roses in Raleigh North Carolina would be March, after any hard frosts and when the buds begin to swell and break their dormancy.

  15. Sharon on November 17th, 2011

    I have 2 knock out bushes planted side by side. One seems to be growing much larger than the other. Should I move one to give the other more space? Also, when should I prune in Illinois? Thank You.

  16. admin on November 19th, 2011

    Hi Sharon
    How far apart have you got them planted now? Knock out roses should be planted about 3 feet apart, so if they’re planted any closer than this it may be a good idea to move it. The best time to do this is when it’s dormant, so either transpant it in fall as it’s going into dormancy to establish some roots before winter or wait until spring as it’s just coming out of dormancy and after any heavy freezes if you live in the colder climate zones of Indiana to do this.
    If they are already planted 3 foot apart, then it’s up to you; you can either move it a bit further apart or when deadheading spent blooms, cut a few inches further down the stems than you normally would to keep it at the height of the other one.
    In Illinois the best time to prune knock out roses is in spring; when the forsythias start to bloom is a good rule of thumb.

  17. Kelly on November 20th, 2011

    I live in Indiana, when should I prune my Knock Out roses?

  18. admin on November 27th, 2011

    Hi Kelly
    the best time to prune your knock out roses in Indiana is in late March/early April after the last freeze.

  19. Linda on November 30th, 2011

    I am in Silver Spring, Maryland, when should I prune our Knock Out roses?

  20. admin on December 7th, 2011

    Hi LInda
    Late March or early April is the best time to prune your knock out roses in Maryland; around the time the forsythia blooms.

  21. jeni b on December 7th, 2011

    I cut my bush down to 12 inches in November,,,Will itreturn in the spring? Will be a burlap bag protect it thru our harsh winters..I am in the Boston area of Massachusetts. I’m new at this and I dont really know if my bush is a knock out rose but I’d liek to plant one in the Spring…Thanks Jeni B

  22. admin on December 10th, 2011

    Hi Jeni
    unfortunately you pruned your rose way too early; the best time to prune a rose in your area is late April, after the last frost. The best thing to do so it survives the harsh Boston winter and returns in spring is to use one of the collars I suggest here and pack it with mulch or soil or leaves. You may need to join two together if the rose is largish. If you can’t get the collars then just mound soil or mulch to a height of 12 inches around the plant. Remove the mulch and rose collar in spring. Let me know how it survives the winter following this advice. I’d be interested to know if the too-early pruning did it any great harm over the winter if it was mulched heavily. Good luck with it

  23. Scott Doll on December 11th, 2011

    We live in Atlanta and planted a number of these beautiful bushes last season. Given our climate zone,when should we prune? They need to be cut back substantially, but we don’t want to damage them.

  24. admin on December 11th, 2011

    Hi Scott
    given your climate zone in Atlanta, you should prune your knock out roses in early March. You can safely prune them down to about 18 inches if you like, without causing damage to them.

  25. shirley on January 3rd, 2012

    I live in the Corpus Christi Tx area. When should I prune my knock out roses?

  26. admin on January 5th, 2012

    Hi Shirley
    February is the best time to prune your knock out roses in Corpus Christi Texas area

  27. Amber on January 9th, 2012

    This will be my second year with my ko roses. The problem I’ve been having is they are all scragly, only growth mainly at the top of the branches. I pruned them a little during the growing season but they didn’t fill in.They were repeat bloomers and are still producing. I want a prettier fuller bush. What can I do to make this happen? ( Panama City Fl.)

  28. admin on January 14th, 2012

    Hi Amber
    the reply I have for you turned into an article on scraggly-looking knock out roses and is located here.

  29. Joan on January 14th, 2012

    Hi,
    I live in Florida in The Villages an hours drive south of Ocala. I think we’re in zone 9 but not totally certain. I have several double knockouts in their second year of growth and doing well. We do get frost sometimes in the winter & even had a freeze last winter. When is the best month to prune?

    I also have a knockout rose tree that now looks a little wild & not as compressed &full as I feel it should. As a note this tree was adopted by a mama bird & she made her nest in it this past spring & I did not notice it until later in the summer when the center of the tree started to look a little bare & discovered the used & abandoned nest. How should I go about trying to trim this tree back so the form & size of the ball will look good?

    Thankyou

  30. admin on January 18th, 2012

    Hi Joan

    you’re right, you are in zone 9 and the best month to prune knock roses in your area of Florida is February.

    With your knock out rose tree, give it a decent prune back in February, measuring about 12 inches out from the center all the way around, pruning it into a ball shape. That should allow it to bush out again once growth commences.

  31. Erin on February 7th, 2012

    I live in northern Kentucky. I have two knock out rose bushes. This past fall when the leaves fell off, I noticed that many of the canes had dark brownish-purplish spots on them. I did some research and found that this could either be black spot or cankers. The recommended treatment was to cut off the infected portion of the canes. My problem is this: the spots go almost all the way to the bottom of most canes. If I cut off ALL the spotted part, I don’t think I’ll be left with much bush… can the bushes survive that? Will the canes grow back? How much is too much to cut off?

  32. admin on February 7th, 2012

    Hi Erin
    I don’t think it’s black spot that is affecting the rose canes as this disease usually only affects the leaves, and the spots are black in color, not brownish-purplish. On roses that are very susceptible to getting black spot, the young stems may get affected, but not the mature canes as is the case you’re describing.

    I don’t think it’s canker either, as canker is die-back of a stem, usually from where a pruning cut has been made, and canker doesn’t appear as spots, it’s more a section or even the whole of the stem that dies back and it looks like dead wood not brownish purplish spots.

    I think what you’re dealing with is downy mildew. This can appear on leaves and canes as purplish-brown irregular shaped spots or blotches. In order to control this fungal disease (which favours damp, humid conditions) you can either prune the infected portion of the canes but that might be too much considering the disease goes to the bottom of most canes (and the breeders of these roses recommend pruning to about 12 inches in height), or you can spray with a fungicide that’s made to control downy mildew and follow the recommended directions on the pack.

  33. bill price on February 7th, 2012

    Thank you for the info i have read, live in florida and starting to trim my knock off’s

  34. admin on February 7th, 2012

    You’re welcome Bill. I’m glad you appreciate the info :) Sounds like you’ve got the timing right for pruning in your area. The University of Florida recommends pruning February or March in North and Central Florida and December in South Florida.

  35. Larry on February 8th, 2012

    I purchased two knockout roses last summer and planted them in large pots. Because are winters can be harsh (upstate NY) I decided to store them in our garage. The garage maintains a temp of around 50 degrees and gets indirect sun through three windows. I discovered this morning that both plants are showing new growth everywhere. I was planning to prune them when I brought them back outdoors in the spring. What should I do?

    Thanks,
    Larry

  36. admin on February 8th, 2012

    Hi Larry
    Obviously the warmer temperatures in your garage in late winter has confused your knock out roses and they think it’s already spring :) It would be too much of a shock to them if you put them outdoors at the moment, esp seeing they have been used to the warmer temp in your garage.

    I’d just leave them where they are and just keep cutting back the new growth to a couple of inches until it’s time to put them outside in spring, then do the usual pruning as mentioned in the article above. Let me know how you go with them. Be sure to feed them with a good rose food after pruning them (always water them before using fertilizer).

    For the knock out roses I have in pots, I only feed them at half the strength of the recommended rate during the growing season, but more frequently (fortnightly) seeing the constant watering of them (esp in Summer) can cause the fertilizer to be leached out. When making up the fertilizer in a watering can I also add some liquid seaweed (again at half the recommended strength). This seems to keep the plant healthy and robust.

  37. Larry on February 8th, 2012

    Thank you and I will keep you posted.

    Larry

  38. Stan on February 8th, 2012

    I live in Jackson, MS, and have about 15 knockout rose bushes that are now 3 years old. When should I prune them? When deadheading, should I cut back to a bud or node?

    Thank you.

  39. admin on February 8th, 2012

    Hi Stan
    Even though the breeders of knock out roses don’t recommend deadheading because the blooms are self cleaning, ie the petals fall off the flower bloom, I still prefer to, as the base of the bloom still stays on the plant and can form into a rose hip that takes energy from the plant; energy better spent on making more flowers in my opinion.

    I personally deadhead the old blooms off just to the next leaf junction or the second leaf junction down (sometimes a bud isn’t visible at the leaf junction – where the leaf meets the stem – but it eventually does appear).

    However when doing the annual prune (the best time to prune in Jackson MS is late February/early March) I don’t worry about cutting to a bud and just prune the whole plant down to 12-18 inches depending on how tall I want it to grow.

  40. noley on February 19th, 2012

    Thank you for all of the info on your website. I live in lower Alabama and was told to prune my rose in February. Now I think I know how to do it. Fixing to give it a try. Thanks again.

  41. admin on February 19th, 2012

    Hi Noley
    Thank you for the thank you :) I’m glad you like the free information I give my readers. You’re right; the best time to prune your roses in lower Alabama is February. You can’t really go wrong with pruning a knock out rose, just cut it back 12-18 inches with a sharp pair of pruners (some folk even use hedging shears) just so long as they’re reasonably sharp so you get a nice clean cut; a jagged cut can lead to dieback (canker). You don’t have to fuss with cutting to an outward facing bud either. I’m sure you’ll nail it :)

  42. Gene on February 19th, 2012

    I live in the St. Louis area of Missouri and my double knockout roses appear to have broken their dormancy. With our relatively warmer winter season the buds are beginning to open. Should I prune these roses now or wait until May. Last yr I cut them by a third in middle winter and another third in early spring and they did quite well as I also transplanted them after final pruning..

  43. admin on February 19th, 2012

    Hi Gene
    Usually the best time to prune knock out roses in St Louis Missouri is late March, after any late frosts. However you normally prune knock out roses just when they are breaking dormancy as is the case with yours. The only trouble with pruning now is that if you do get a late frost, the soft new growth could be damaged. If that happens you could always prune off any frost damaged new growth in late March, so maybe prune now but leave a couple of inches more than what you might prune to normally (you can prune down anywhere from 12-18 inches or more depending on how tall you want them to grow) just in case a late frost hits. You know your local area best; do you normally get late frosts?

  44. Mike Kormanik on March 7th, 2012

    Hi,

    Last spring we planted 57 double knockout roses as a border around our property.

    When should we prune them for the first time. We live in New York City and the winter has been mild.

  45. admin on March 7th, 2012

    Hi Mike
    How beautiful must that border of 57 double knockouts look:). Late March is the best time to prune knock out roses in New York City; when the buds become swollen and visible.

    Regarding the first time to prune them, some rosarians suggest not pruning roses in their first year to allow them to establish and develop their natural shape. The downside to this though is that your knock out roses will start growing taller in the second growing season and with that, will start looking rather lanky by this time next year.

    I think the advice not to prune the first year is geared toward roses other than the landscape type roses like knockouts.

    Personally I would prune them this year to develop a fuller rose bush (it is still going to develop its shape regardlesss); there would be nothing worse than a border full of lanky looking rose bushes. Follow the pruning advice above and they should do well.

  46. Ruth on March 7th, 2012

    Planted knockouts & carpet roses in fall last year. Would you prune this spring, or wait until next spring?

  47. admin on March 8th, 2012

    Hi Ruth
    the roses are still really establishing after only 6 months so I wouldn’t do the normal type of heavy annual prune on them. Maybe just give them a bit of a trim – nothing too severe – to keep them bushy and well shaped.

    You can usually prune knockouts and carpet roses down to 12 inches, so for yours I’d cut them back by a third of their current height, then next spring do the usual annual prune.

  48. Janice McCarty on March 10th, 2012

    Last year during the summer my rose bushes began to lose their leaves. They seemed to dry up and turn yellow. It was not because of lack of watering. What caused this? They were so beautiful before this.

  49. admin on March 10th, 2012

    Hi Janice
    Those symptoms could be caused by overwatering, poor drainage, lack of nutrients in the soil, over fertilizing or leaf diseases like black spot.

    Check the area of soil where the roses are planted. Even though you are giving them plenty of water, is the area retaining the water when you water it? Feel around the base of the plants after you water them. Get a longish stick and stick that into the soil at various places to check that the water is penetrating deep enough into the soil and not just into the top few inches.

    Are you overwatering your roses? Check the soil before you water to make sure it needs watering in the first place. Check that the soil isn’t waterlogged an hour or two after watering due to poor drainage.

    Do you fertilize regularly through the growing season and follow the recommended mixing rate and application directions? Start with these basics first to see if that helps with the yellowing and subsequent loss of your rose leaves.

  50. mary on March 17th, 2012

    I live in Alabama zone 8 and waited to prune my knockouts and now they already have buds and a couple of blooms. It has been really warm! Is it ok to prune them now will they put out new buds?

  51. admin on March 18th, 2012

    Hi Mary
    It should be OK to prune them now. Just cut them down to 12-18 inches in height. Any new buds on the 12-18 inch canes will still keep growing, and yes they will still keep putting out new buds. Be sure to give them some fertilizer when you finish pruning and follow the recommended dosage rates on the pack.

  52. Amber on March 31st, 2012

    I just transplanted 2 knockout roses. I have been watering thoroughly but think I need to cut them back a little so the energy will go to the root for establishment. What are your suggestions on pruning after transplanting?

  53. admin on March 31st, 2012

    Hi Amber
    You can probably give them a light prune but the main thing is giving them plenty of water as they’ve lost part of their root mass. Do not give your knockouts any type of fertilizer until they are established in their new position (you’ll start seeing new growth) and then only at half strength.

    The only thing I’d give them in addition to lots of water is liquid seaweed (which is not a fertilizer but more a soil conditioner) made up in a watering can at half the recommended strength and apply this once a week after you’ve given them a good soak of plain water first. As you can read in this article about liquid seaweed, it helps stimulate root growth, which is what your knock out roses needs after transplanting.

  54. Carrie on April 2nd, 2012

    I have three knockouts growing nicely over the past years. I’m redesigning and I want to relocate them within my garden. What is the best way to move them – and, living in Virginia, when is the best time?

    Thank you,
    Carrie

  55. admin on April 3rd, 2012

    Hi Carrie
    My reply ended up too lengthy for the comment box, so I’ve answered your question more fully in this new article: transplanting-knockout-roses. Follow these guidelines for successfully relocating them.

  56. Mary myers on April 3rd, 2012

    I planted my knockout rosebush 3years ago in Md. And never pruned it. It is 4 ft.tall and very full. Can I prune now to make it about 3ft tall?

  57. admin on April 4th, 2012

    Hi Mary
    late March/early April is the best time to do the main annual prune in Maryland, so you can safely prune them now. If you only want to prune your knockout rose bush down to 3 foot that’s fine, however the breeder of the knockout rose says they can be safely pruned down to 12-18 inches in height.

  58. Linda on April 8th, 2012

    I live in South Carolina and my knock outs just started to bloom. Is it too late to shape them? They are getting so big and I want to tame them down a bit. Maybe cutting 12 inches off all the way around. Will this hurt the bloom?

  59. admin on April 9th, 2012

    Hi Linda
    If your knock outs are getting too big, you can cut them back 12 inches (or more if you wish). The only downside is that you’ll have to wait around 6 weeks for them to bloom again after this prune. Make sure you feed them with a quality fertilizer after pruning them (don’t be tempted to overfeed them, just stick to the recommended dosage rates).

  60. Cara on September 12th, 2012

    I have 26 red Knockout roses planted down the side of my lawn. They have grown to over 6 feet tall. They have heavy leaf coverage and bloom profusely in the early spring, but then lose a lot of leaves and have very few blooms the rest of the summer. I feed them each spring with either Miracle Grow for roses or a fertilizer made specifically for Knockouts. What suggestions do you have for me? I want to take down the height so they are 3-4 feet tall after new growth, but I’m afraid I’ll prune them so severely that they’ll die. I also need to know how often to feed them. I live in Northwest Georgia. Our last hard freeze is usually in February, but we continue to have frost until late April. Our roses here usually starting putting on new growth in mid February. I’ve prunded them in January in the past. Should I wait until later? Thanks!

  61. admin on September 14th, 2012

    Hi Cara
    The breeders of knock out roses say that it is safe to prune them down to 18 inches, however I wouldn’t do this just yet with yours. Knock outs usually grow 3-4 feet, so at 6 feet I’m assuming you don’t prune your roses down this low at pruning time? If I were you, I’d prune them by half in late summer/early autumn, then give them some fertilizer according to the dosage directions.

    Then in January/Feb when doing the annual prune, I’d reduce the bushes down by half of their height. What you are doing here is gradually reducing the height of the bush so you can then prune at a lower height which in turn will cause the bush to not grow so tall. You may have to do this twice-a-year prune a couple of years in a row, until you get to the point where you can do an annual prune of 18-24 inches so the bushes don’t exceed the 3-4 foot mark.

    You could try waiting til early Feb to do the annual prune as that is one month’s less growth the plant will put on at the beginning of the growing season.

    Regarding how often to feed them; you should feed your roses after you’ve pruned them in early Spring, then again 8 weeks later, and then again in another 8 weeks (or in your case after you’ve done that 2nd prune in late summer/early autumn). Always follow the dosage directions on the container.

    As far as your roses losing a lot of leaves, here are some things to check at the time it occurs: check the leaves for insect pests or fungal disease like black spot which can cause leaf fall. Not enough water, or too much water can also cause leaf fall. Check drainage. Check that you are not using too much fertilizer when feeding; always follow dosage directions on label.

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