Gardening Tips: Caring for Knock Out Roses

These are my Knock Out rose bushes at the beginning of last spring. By the end of summer, they were six feet tall!

I remember as a child spending my summers in Atlanta with my grandparents, affectionately called Dear and Gramps. I would watch Gramps tend to his flower and vegetable gardens hoping to one day do the same with my own. It seemed to bring him peace and tranquility to work in his gardens. Unlike my cousins, I always wanted to assist him, especially when it was time to pick the strawberries. Yummy.

Now that I have my own garden, I’ve realized that its a lot of hard work! My grandfather made it seem so easy. A lot of time and effort has to go into keeping up the appearance and well-being of your plants and flowers. At one point I shyed away from gardening thinking I didn’t have a green thumb like my grandfather, but I really wanted a rose bush. Roses have always been my favorite flower. They’re so fragrant and beautiful. After doing research, I found that Knock Out rose bushes are by the far the easiest rose bush to care for. You don’t need a green thumb but just a little time each week to tend to their needs. So a few years ago for Valentine’s Day instead of the dozen of pink roses my husband usually gave me, I was quite surprised to see four Knock Out rose bushes in containers. He planted them for me once the danger of the last frost was over, and I have cared for them ever since. If you are looking for a low-maintenance rose bush, you should check out the Knock Out rose bush.

Knock Out Rose History

William Radler, a rose breeder in Wisconsin was fascinated by roses from a young age. When he was only nine-years old, he spent his allowance on a rose plant determined to care for it. As a rose breeder, he was determined to create a heat-tolerant and disease-resistant rose. He tested over 500 seedlings growing under a fluorescent light in the basement of his home. In 1988, he discovered the first Knock Out rose by cross-breeding Razzle Dazzle and Carefree Beauty.

Knock Out roses are low-maintenance roses that are perfect for people who love roses but do not necessarily have a green thumb. This breed of roses is heat-tolerant and can grow in any area of the United States. Ranging in a variety of colors such as red, pink, white and yellow, Knock Out roses can grow up to 6 feet tall and 6 feet wide if left unpruned. Their bloom period is from spring to early fall, with continuous blooms throughout which will deadhead themselves. They are ideally planted along a foundation or sidewalk area to add curb appeal to your front yard, making you the envy of the neighborhood.

Preparing the Rose Bed

Select an area in your landscape to plant your Knock Out roses. The area should have six to eight hours a day of full sunshine with some afternoon shade. The soil should drain well, therefore avoiding the bottom of a sloped area. Contact your county extension to conduct a soil analysis for you on site or take a soil sample to them. Soil pH for roses should be between 6.0 to 7.0 for optimum growth. The results of the soil test will reveal the amendments to enrich your soil before planting the roses.

Remove and discard grass, weeds, plants, rocks and debris from the planting area. You may need a tiller to clear and smooth the area. A tiller can be rented at your local home improvement store. Amend the soil by spreading a 4-inch layer of organic matter such as compost as well as 3 pounds of superphosphate per 100 square feet of the area. Mix together with a garden fork to a depth of 10 to 12 inches.

Planting Time

Decide how many Knock Out roses you would like to plant in the garden bed. Knock Out rose bushes can grow from 4 to 6 feet wide. Set the roses still in the containers in the bed, spacing them at least 4 feet apart to allow for growth and room to walk in-between the rose bushes. According to the University of Missouri, bushes in general should be planted in odd numbers such as planting five or seven bushes together.

With a digging shovel, dig a hole twice the width of the nursery container but the same deepness, approximately 12 inches. Carefully remove the Knock Out rose from the container. (Wear heavy duty gloves to protect yourself from the thorns.) Discard damaged canes and roots. If the soil is dry, water it first before planting. Place the rose bush in the center of the hole and spread the roots. Make sure to set the bud union 1 inch above soil level in USDA zones 6 to 10 and 1 inch under soil level in USDA zone 5. Refill the hole, tamping the soil around the roots. Water deeply until water puddles on top of the soil. Plant the next Knock Out rose bush 4 feet apart.

Care and Maintenance

After planting, spread a 3-inch layer of mulch, such as pine straw or wood chips, throughout the rose garden. Do not use wood chips if the garden is along the foundation of your home for this could attract termites. Start the mulch 6 inches away from the base of each rose bush. The mulch will keep the ground moist and prevent weeds from growing. Before the first frost, apply another layer of mulch to keep the soil warm during the winter months.

Water the Knock Out roses during the growing season two times a week if rainfall is under 1 inch per week. Use a soaker hose on the soil avoiding the trunk of the rose bush and the foliage. Water early in the morning.

Apply 1 cup of general purpose fertilizer (10-10-10) or a rose food three times a year to your Knock Out rose bushes. Apply in the spring after the rose bush has been pruned, again in the middle of June and in the middle of July. Never fertilize after August 15, according to the University of Illinois Extension, because the rose bush needs to cease growth to prepare for dormancy. Sprinkle the fertilizer beginning 6 to 8 inches away from the base and spreading out to 18 inches. Scratch into the soil and water deeply to prevent the roots from burning.

Prune your Knock Out rose bushes in the early spring after the danger of the last frost has passed. Prune the canes back to 12 inches. During the growing season, remove spent roses, diseased or damaged canes and foliage. This will prevent further spread of disease and ward off pests.



71 thoughts on “Gardening Tips: Caring for Knock Out Roses

    • Thank you. I need to prune them in a few weeks and fertilize which is why I wrote this blog as more a of reminder to myself that its almost time to care for them again. I also have a vegetable garden in the backyard with collards, cabbage and brocolli but I need to change that out in a few weeks to prepare for my summer garden. Its fun and rewarding and saves money.

    • I been raising knock outs for 3 years now and know they love a dash of Epsom Salt least once a month. It has magnesium sulfate in it.

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  2. My double knockouts are three yrs old and gorgeous at first bloom. Then they start to look puny and there leaves start turning yellowish? What is causing this? Over watering? Please help!

  3. Hi, Adrienne!
    I know exactly what you mean about the roses being so beautiful at first bloom and then they begin to look puny and leaves change to yellow. I’ve noticed for some reason that Japanese Beetles tend to begin living in my blooms after the first bloom until I sprinkle Sevin on them. Those ugly things suck the life out of roses in general which can cause leaves to turn and the blooms appear smaller during the next bloom period. Also, are you fertilizing your roses after the first bloom? That will help with the continous blooms. They may have a lack of nitrogen. I use a simple Rose Food instead of a general fertilizer. Plus, I know Knock Outs are supposed to “deadhead” themselves, but I do it anyway. They are still getting nutrients and water which need to go to the upcoming blooms. My Knock Outs are about 6 feet tall right now (no seriously) I’m 5’6 and hubby is 5’9 and they are taller than us! So I water them more often, maybe every other day, to ensure they receive enough water.

    I hope this helped. Let me know how your roses are progressing.

  4. Very nice article, I am getting ready to plant some more knockout roses> just a little FYI though, there is no such thing as a white knockout rose. There is a “whiteout” rose, but it is not related to knockouts.

  5. This is the third year for my knock out roses. They have done extremely well. I pruned them this spring and they are growing well and I’m seeng the first rosebuds. However something is eating the leaves as I’m seeing holes in the leaves and a white substance on them as well. Have searched the Internet but can’t determine what this might be. Please help

  6. We just planted the roses, but they are drooping, bad.mwhen should I water…early am? Will they come back to life?!

    • I would give them a little water this AM and see if they perk up. I do all my watering in early evening, that’s when I’m out in the gardens.

    • Hello, Michael. The best time to water the roses would be early in the morning using a water hose at the base of the plant to avoid getting the foliage wet. Water them deeply for about 3 to 5 minutes each. Also, since you just planted them, they need to be watered everyday for two weeks in order to establish the roots. Afterwards, water about every 2 to 3 days depending upon the weather. Also, feed them with a rose food. I use a Knock Out rose fertilizer I bought at Home Depot. Follow the directions on the label but don’t fertilize after August 15th. I hope this helps. Keep me posted.

  7. Can prune my roses now even though they are blooming, mainly some branches are taller than others. I want to even them out in height.

    • Yes, it is fine to prune rose bushes during this time of year to maintain neatness and the height you prefer. I wouldn’t advise pruning them after October 15th. They will need to prepare for the winter.

  8. I have 4 year old Knock Out roses that bloomed beautifully this spring. I noticed holes on the leaves (I found tiny light green worm on the bottom of a leaf)so I treated with a recommended insect product and now have no blooms at all and don’t see any buds. These bushes have been very successful the past 3 seasons with very little maintenance on my part so I’m wondering what I could do to bring the blooms back. Any advice?

    • Hi, Trish. I honestly have no idea why your roses are not blooming at the present moment. That does seem weird but I do know bugs will suck the life out of them. I had Japanese Beetles a few seasons ago that made my blooms smaller for a few months. I sprinkled Sevin on them and haven’t had a problem since. I also feed my Knock Outs with a Knock Out rose food that produces beautiful blooms. Perhaps try fertilizing. Let me know what happens.

  9. We planted ours about 3 weeks ago. Looked great until this week when all the blooms fell off and 90% of the leaves fell off. We have had a lot of rain and when they started looking sickly I watered more. Too much? Should I leave alone and see if they come “back to life”?

    • You may want to have a soil test done. They sell the kits at home improvement stores or your local/county agriculture department can also do the test as well. The soil may be missing some nutrients that your roses need or has too much of something.

  10. I just went out about 9 pm and harvested more than 50 bugs from my KO Roses. In one night they did lots of damage to the leaves.
    Is there something besides dusting with Sevin?

  11. Poor drainage and heavy rains will drown the roots and mycorrhiza of many plants, including roses. Unfortunately, the symptoms look much the same as those of underwatering, causing many gardeners to worsen the situation when their plants look stressed.

  12. My husband bought me a knock out rose bush for my birthday on June 10th. I planted it but sometimes it looks healthier than others. Also it still looks like a tree instead of a bush. I am 7 and a half months in a high risk pregnancy so I wasn’t able to get down there and pull out all of my weeds. Would the weeds stop my plant from growing?

  13. Oh also.. I have been watering it everyday because its been between 90 and 95 degrees for the past few weeks. I didn’t know anything about fertilizer or a soil test until I read your article. I do cut off the dead roses at an angle once they are completely gone. And the dead leaves. This is my first rose bush and I just need some advise. Thanks

  14. I have 10 new Knock Out Roses planted this year. They are small now. If I prune them every spring, will they ever grow to six feet tall? I’m not sure how pruning affects the yearly growth.

    • I believe it may depend on the type of Knock Outs you have. Mine grow over 6 feet maybe even 8 feet tall but the one I gave my mother can’t seem to get passed 15 inches and it wasn’t from the same bunch my husband gave me. However, still prune them as needed and cut them down to 12 inches in early spring after the last frost for your area.

  15. The best time to plant knockout roses is in the spring after last frost. I have had knockout roses for about 7 years now and they are very beautiful every spring. I’ve never fertilized them but only when I first planted them and I watered them every day for the first couple of weeks then mother nature took over after that.After the 3 or 4th season I started deadheading a little because they got so big they starting spreading over the patio so I had to trim them back. Other than that they are drought tolerant and just take care of themselves.They are drought tolerant, pest resistant, very hardy and self cleaning . They’re a knockout so I don’t have to knock myself out. Karen Keating, Athens, Ga.

  16. Hi I just read your article on knockout roses. I’m looking to plant some along the front of my house. How soon should I do it at the next break in temperature because I do want them to bloom pretty for spring and summer into fall. Very excited to be doing something new and different in my landscaping area.

    • Hi Angela! I’m not sure what city you live in but it is best to wait until the last frost has ended otherwise the ground will refreeze and could possibly damage the roots. But Knock Outs are so easy to grow its hard to kill them. LOL!

      • What’s the lowest Temp i should leave my knockout’s i just purchased in gal. container’s, I live in Southeastern Indiana and its going to be 38 overnight, Should i place them in basement or garage.

      • I would bring them in but don’t set them directly on the cold concrete of the basement or garage. If you have any old towels, set them on top. The temp of the concrete could go lower than 38. Also wait until after the last frost before planting them in the ground. I hope my information is helpful.


        Sent from my iPhone


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  18. Thank You Candace, For the advice, There doing great, Hoping to get them in the ground Mother’s Day weekend.

  19. I had a gorgeous pink knock out rose for 7 yrs. The last two yrs I noticed these ugly deformed branches that came out , very very stickery yet my rose bloomed beautifully having approx. A thousand blooms all at one time…so beautiful I had to take a pix of it. I tried cutting the ugly branches off but they came back with even more…then this year…totally dead…nothing. I was devastated. So I pulled it out and bought me a new one to start all over…in fact just planted it yesterday. So could you tell me what went wrong? Thanks in advance. #rosesuckercontrol

  20. I have knock out roses and thought nothing would harm them. I went to my Ag person when some of my roses (knockout) started dying. She found on the U of Iii Ag that there is a small mite so small it can only be seen with a microscope and there is nothing available “yet” that will kill them, the paper recommends digging them up and moving them at least a 100 feet away from where they were dug up and burn the plants. somethimes this mite will kill the plant in one two three or more years no cure see Pamela Hutton above for how the mite works. I found some branches and plants this year and dug them out but you can’t tell if the mites are still in the hole where the plant was taken from.

  21. I had just purchased my first knock out rose bush. Does anyone know that if I have a cement slab but place about a 3 ft dirt berm, will it affect the roots and/or will it still be able to grow?

  22. My ten pink knock-outs, and also my pink drift roses, are in their 2nd year. They were drop-dead gorgeous all of May. This week, all the beautiful blooms are done, and falling off. So I will feed them, and I want to dead-head them. But….do I need to do the careful cutting at the next lower 5-leaved branch, or can I just cut off the dead flowers? It would take me a very long time to do the former.

    • Hi Barbara! Mine look the same exact way right now. No beautiful blooms! It’s best to just do the regular deadheading and clip the flower part off and tidy up any wayward looking stems or canes before the next bloom session. Hope this helps. Keep me posted!

      Sent from my iPhone


  23. I would like to tell you how I am growing all the knockout roses. I moved into my new town-home but didn’t notice the soil surrounding my gated patio or the soil on the outside of my fence. Turns out on the inside of the fence area around my patio it was loaded with small rocks about 1 ft deep on top of that were plastic bags and mulch then on top of that was the black weed cloth and on top of that was more mulch. I had to hire someone to remove all that bad stuff. Not one worm was to be found, the soil was dead. I bought great organic garden soil and mixed it in with the dead soil and threw dead fish, coffee grounds, bone meal and watered it all with seaweed emulsion and Alaskan fish emulsion. I let it sit like that for a couple of weeks. I ordered double knockout roses. When I planted them I dug the big hole and buried a cut up fish a cup of used coffee grounds from Starbucks. some bone meal covered it with good organic garden soil and again watered it. I placed the knockouts in the ground and watered it. I waited and hour and watered it again with seaweed emulsion. . As a precaution today I watered all the knockout rose with one heaping teaspoon of Epsom salt per gallon of water and watered all roses with that solution

    Just to let you know here in Florida it has poured heavily every day since July 1st which is when I started to take notice. Not one leaf had black spots or yellowed on any of the knockouts.

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  38. We have several knock out roses. They are in direct sun and we’ll drained. They are about 5 years old and only about 2 – 3 ft tall. At the end of the last season, they almost looked like they were dying. Any suggestions to pep then up. We live in southern Mo. They haven’t started putting out any green yet this year.

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