Knock Out roses are some of the easiest, most rewarding roses to grow! Our yard has 12 fuscia and light pink Knock Out rose bushes. The joy of Knock Outs is their constant blooms from spring until fall. Surprisingly, these rose bushes can grow to be quite large if not maintained. Neglecting them is easy since they require little upkeep and are nearly impossible to kill. I’ve neglected a few of mine to the point of needing some serious pruning. Now is the time to prune roses, so let’s take a look at a few tips on How and When to Prune Knock Out Roses.
This is embarrassing. Just look at that rose bush! I measured it at a sprawling 9 feet tall. Insane! I didn’t even realize Knock Out roses could grow that high. But wow, this one looks like a hot mess.
When to Prune
The beauty of Knock Out roses is that they can be pruned nearly any time without sacrificing beautiful blooms. Here in the south, we can expect the first flush of blooms around Mother’s Day in early May. This will be the largest flush of blooms. Then the plant will enter a resting phase and then burst with repeat blooms every few weeks. Maintainence pruning can be done during the resting phase. It is also a good time to cut off withered blooms, but not necessary.
Heavy pruning though should be done in late February in warm, southern climates or in March for the moderate to cool climates. The only time I do not recommend pruning is in the fall. It could trigger new growth that will not have time to harden before winter. One exception is if you live in the deep south then pruning any time of the year is acceptable.
Recommended Pruning Tools
As a brand ambassador for Troy-Bilt, I have the opportunity to try and review a multitude of lawn and garden tools. Listed below are 3 of my favorite and most used pruning tools. (Amazon affliate links provided for your shopping convenience)
When trimming roses for floral arrangements or controlling overall shape, I really love my Troy-Bilt Bypass Pruners. They are very sharp, cut through rose stems like butter and fit nicely in my hand.
For woody rose stems over 1/2 inch thick, I recommend using a telescoping bypass lopper. This particular lopper has adjustable telescoping handles, allowing you to easily prune thick, thorny branches without having to reach your hands inside the bush.
This recommendation might surprise you but hedge trimmers can be used on Knock Out rose bushes. We have several Knock Out’s grouped together to form a hedge row. Maintaining and shaping a rose hedge is easy when using this cordless hedge trimmer.
Use a clean and sanitized hand pruner for stems less than 1/2″ or a lopper for stems over 1/2″ inch. Cut the stems back to a 5-leaf grouping or an outward-facing bud (if pruning during the growing season). Remove and discard any dead, crowded, crossed or rubbing branches. The goal is to open up the plant’s center and eliminate unnecessary suckers or random shoots. Cut the rose bush back by 1/3 to 1/2 the size. With severe heavy pruning, the plant can be cut down to 18″-36″ depending on how large the rosh bush was.
Tip: Wipe off the cutting blades of the pruner with antibacterial wipes before moving to a different rose bush.
I severly cut that 9 foot tall bush back to about 30″ high. New growth has appeared within just one week since pruning.
Here are a few before pics of the overgrown rose hedge.
And here is the hedge after being trimmed with the cordless hedge trimmer. It needs a bit of fine tweeking with the hand pruner, but overal looks much better.
Start fertilizing with a quality, slow release rose fertilizer in April or at the first sign of significant new growth. In just a couple months the rose hedge will be bursting with blooms look even better than this!
I can’t wait to see how healthy and strong the roses will be this year!
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If you are new to rose gardening, then I recommend reading my Brown Thumb Gardener’s Guide to Easy Roses.
Happy Gardening!
KIM
I’m totally ready for Spring in Florida! This post came at the right time for me, Kim! I just bought a pink Knock Out Rose for the very first time. I’m definitely pinning this info for future use. Can I plant this in a large pot instead of the ground? I was hoping to put it out near the pool.
Hi Nancie! Yes you can plant it in a large pot but be aware it will grow fast and you will have to trim it a few times during the summer to control and maintain the size and shape. Congrats on the purchase… it will look gorgeous next to a pool. 😉
Absolutely gorgeous! I had a beautiful swath of these in a lower bed by my pool and sadly they were attacked by some disease in year 2 that looked like they had ginormous mud nests hanging from them and then the leaves were gone slowly and steady. I had a landscaper tell me no more roses because my soil is probably contaminated😢 I will more than likely try a new location in another year.
Hi Lisa! That disease sounds awful! Yes I would try them in a different spot for sure. Thanks so much! Have a great week! ~ KIM
I have 7 double knockout roses that are 5 ft wide and 6 foot tall!! They keep getting these large heavy clusters on them. How can I trim them and make them healthy here in the Arkansas heat,
Hi Tracy! I dedicated a paragraph in that blog post towards talking about when exactly to prune and how much. Go ahead and cut off the heavy clusters and bring them inside to enjoy. Just don’t do any severe pruning (like I did) until Feb or early March. Light pruning is fine right now. Happy Gardening! ~KIM
Hi, I live in Oregon, in the Willamette valley, we have clay soil, never been planted with anything. Want to do roses. Not sure which type.
Hi Melinda!
In your area, you can plant any rose you would like. Knockouts are the easiest to grow, are very disease resistant and grow fast!
How short can you cut knock out roses back and whats the best time of year to do so (I live in Houston, TX)? I have five of them that have been in about two years and are now about 3-4′ tall, and wanting to clean them up.
Hi Steve!
You can trim them back at any time during the year in Houston. I just recommed that if you want to do severe pruning that you wait until late February in your area. (PS- keeping your city in my prayers).
Warm Regards,
KIM
I am in Central Texas and I pruned my knockout roses in January. There doesn’t appear to be any new growth. Do you know how long it will take for them to grow and bloom? Is there anything I need to do to help them?
Hi Susan!
Don’t worry it’s still early for pruned bushes to start growing. You all had quite a drop in temps a few weeks ago too. They will be start putting out new growth soon. When you start seeing new growth add a granulated rose food fertilizer around the base of each rose plant and work it into the top few inches of soil. Your first huge flush of blooms will probably occur a week or two before Mother’s Day, if not sooner.
Best,
KIM
It is the beginning of August and my knock out roses are not looking real god; they are 11 years old and the bases are thick and white looking should I prune them real low are just remove them and plant new oness.
Hi Betty! Depending on where you live, you can technically cut your knock outs back anytime, but I recommend doing a drastic prune in late winter/early spring. Have you pruned them lately? For the health of the plant you should prune it back by 1/3 to 1/2. You can do that right now even and will have a beautiful flush of blooms come fall. The white thick bases are a sign of age. They might be on their last legs. It’s a call you can make, but I recommend pruning first before ripping them out. Hope that helps! ~ KIM
Hello, I love the information you have given on Knock Out Roses. My question is do you fertilize more than once a year and what type fertilizer, 3 month, 9 month etc.?
Thanks Teresa! I personally only fertilize knockouts in the early spring with a slow release granular rose fertilizer which I work into the soil around the base.
What is the name of fertilizer
I use Bayer Advanced Garden all in one rose fertilizer.
I live in PA, zone 5. I have 4 knock outs – 2 are 6 years old, and the other 2 are only 2 years old. I was intending to prune them before the first frost, but time has gotten the best of me. We had a mild frost last week, and then this am, it was 29 degrees, so obviously there was a glistening of the white stuff in the grass and on the cars this morning! My roses are about 4-5 feet tall, x 3-4 feet wide. I’d like to maintain them for next summer at about 3-4 feet tall. Do I prune a little now, and then do it again in the Feb of 2019, or at this point, do I just wait until Feb 2019 to take them down to about 30 inches so that they will then be about 3 or 4 feet tall during next summer? I did well pruning this past year, but I was hesitant to take too much off so I only took about a foot and a half off – but then they just got too big eventhough I was maintaining them several times throughout the summer, I’d love to only have to do that maybe once to control the height and therefore would love to take them down to two and a half feet in Feb so that they don’t go crazy on me again next summer. Should I wait until Feb to do this? Thanks in advance!
Hi Laura!
Thank you so much for this question! Yes WAIT! Wait until late February or even Early March to prune, especially since you are in zone 5. You want to prune ideally before you see new growth but even if you have a bit of new growth come late winter/early spring in your zone, you can prune. Go ahead and take them down during that time. When new growth starts then put a handful of rose fertilizer around them and work it into the base soil. They will explode in blooms and growth late May-June. The risk of pruning late fall in your zone is that if you were to get an “Indian Summer” the the roses will push out new growth and within a week you will have frost which would kill the new buds… not good, so that is why you specifically should wait for your area. Hope that helps! ~ KIM
In Kentucky and have a cluster of three knock outs that had gotten to about 5 feet. I pruned them back today (I know, a little late). But would really love to do a little more severe, like back to about the 36” height you mentioned in the article.
But, there’s already leaf growth on them. Have I waited to late?
I’d just like to see them be lower growth and less woody showing at the bottom.
Hi Tonya!
I’m so sorry, I somehow missed your comment! By now I’m sure your roses are in full bloom. If you really want to cut them back again, you can but wait for this first beautiful flush to finish or you could simply wait until next Feb/March. That is what I personally would do for the health of the plant.
Hope that helps, even though a bit late!
Best,
KIM
Hello from Dallas TX. I have a knockout rose that has a large barren stalk about 3ft from ground to foliage. How to prune to get foliage and blossoms along the lower stem?
Appreciate ur advice!
Hi Patricia!
I’m guessing that stem is quite old. Is it woody and thick? I would go ahead and cut it back to the base of the plant.I can’t really help you more without photos to help diagnose the issue. Hope that helps some. Feel free to email me pics if you want (sandandsisal@gmail.com)
Best,
\KIM
This info is very helpful. But I must caution everyone regarding pruning of knockout roses with fungus. I recently pruned my knockout rose. I did have a thorn in my right arm that I am mediately removed however I wasn’t aware of that the one that was in my left arm. About two weeks after pruning I noticed red spots on both arms radiating down to my hand.
Unfortunately after research and talking with my doctor I had developed Gardeners disease. I am now on an antifungal medication for three months please be aware of this danger.
Hello! I am in Wisconsin and have 4 knock out rose bushes that were here when we bought our house- if I had to guess I would say they are 20+ years old. Our first year here they were gorgeous and probably 6’x6’! Due to were they are we ended up cutting them back to a more manageable size. This is the 4th summer we have been here and each fall we cut the bush down to about 18” high (something we had heard to do)Usually they come back and are about 2’-3’ high- but never to the 6’ height they were when we got here. This summer they are maybe 2’ tall and the new branches keep falling over. Are we doing something wrong or are they just getting old? The inner branches are woody and tend to rot off. Help! I don’t want to loose them as they are usually so gorgeous to look at!
Hi Kendra!
Thanks for reaching out about your roses! I would say it’s time to say goodbye to those bushes. They are just simply too old. When the bases get really thick and woody then that is when I see problems start and disease sets in. In my experience you should get a good 10 years out of the knockouts but not much more than that. They are so inexpensive any more and grow so fast that I would consider replacing them. The newer varieties are so much more hardier and disease resistant and produce some really beautiful blooms.
Hope that helps!
KIM