How To Care For Knock Out Roses

knock out roses

knock out roses

Updated on 2/20/2024
Emma DowneyBy Emma Downey
Gardening Expert
Learn More about Emma Downey

Knock Out roses have been one of the most popularly purchased landscaping plants across the country since you first brought them to market one hundred and fifty years ago.

In your garden, Knock Out roses can perform a variety of functions, including those of foundation plantings, border plants, low hedges, or even specimen plants.

They are one of the roses that bloom for the longest period of time, require the least amount of maintenance, and are the most resistant to both pests and diseases. Even the devastating black spot disease, which is a common problem for rose farmers, cannot affect Knock Out roses. Black spot is almost certainly what killed your rose shrub if it did, and who hasn't experienced that?

Roses are notoriously challenging plants to cultivate. They behave like diva plants in the garden, demanding continual attention and care in the form of trimming, spraying, and feeding. However, thanks to Knock Out roses, growing roses is now within reach of most gardeners. It is not even necessary to deadhead the plants because they will drop their own blossoms and continue to bloom even without your assistance.

"Knock Out doesn't know it's a rose," rose breeder Bill Radler, who was responsible for developing the variety, said in an interview with Wisconsin PBS in 2001, one year after he released his creation to the public for purchase.

The immediate success of the low-maintenance and disease-resistant roses led to the development of a family of roses known as Knock Out roses. These roses include the petite Knock Out, which is only 18 inches tall and has flowers that are an average of 1 1/2 inches in diameter; the Double Knock Out; and Knock Outs that bloom in a variety of colors, such as coral, yellow, pink, and white.

There isn't a plant nursery in the world where you can swing a pair of pruners without striking a pallet of Knock Out roses these days. What you need to know to grow them, as well as ideas on how to use them to bring color to your yard, patio, and garden, are outlined in the following paragraphs.

  • Botanical Name: Rosa Radrazz
  • Common name for this flower: Knock Out Rose
  • Period of Flowering: Spring through Autumn
  • The USDA hardiness zones range from 4 to 9.

Introducing Knock Out Roses Into The Garden

knock out roses

knock out roses

You should plant Knock Outs in the spring or fall. When temperatures are moderate, they will have a lower likelihood of experiencing transplant shock.

Choose a location that will provide your Knock Out roses with six to eight hours of sunlight each day. They are tolerant of a certain amount of shade, but they produce their greatest flowers when grown in full sun.

A minimum of three feet should separate them. This allows them to attain their full size while still having a sufficient area for adequate air circulation, which is essential for the prevention of disease.

How To Take Care Of Knock Out Roses

Low maintenance doesn't mean any maintenance. Here is a guide to ensuring that your Knock Outs continue to look absolutely stunning.

The ideal growing environment for Knock Outs is neutral soil with a pH ranging from 5.5 to 6.5. You can adjust the pH of your soil by using various amendments to suit your needs. There are test kits available for determining the pH of your soil that you can use at home, or the extension office in your area should be able to perform the analysis for you.

knock out roses

knock out roses

Maintain a consistent watering schedule throughout the growing season. The amount of water that you need to give your rose depends on where you live and the average amount of rainfall that area receives. They are not plants that require a lot of water and can survive in dry conditions, but they do require a couple of liters of water once a week when they are actively growing.

During the growing season, you should fertilize them once per month or every other month. Utilize a rose food that is well-balanced. In the late summer, you should stop fertilizing the plant so that it can focus its efforts on preparing its roots for the next winter.

When new shoots begin to sprout from the canes in the late winter or early spring, then is the time to prune your roses. Every two or three years, give the shrub a severe trimming that involves removing around two-thirds of it.

There is no requirement for you to deadhead them. As was said previously, Knock Outs continue to bloom even if you do not remove the spent flowers, making them a helpful companion for the slacker gardener. However, deadheading might make them appear more organized.

How To Cultivate Knock Out Roses In Containers

It is possible to cultivate Knock Out roses in a container, yes. Choose a pot that has good drainage and is at least two sizes larger than the one the rose came in to plant it in. This allows for more room for it to expand. During the growing season, water the plant twice every week. Because the rose's root system is more likely to freeze in a container, you may need to bring the potted rose indoors during the winter months, depending on where you live. However, this is not always necessary. If you live in a region that experiences extremely harsh winters, you should bring your roses inside and preserve them in a cool, dark location such as your garage or basement.

When fully mature, Petite Knock Out rose plants reach a height of 18 inches and are ideally suited for use in ornamental containers. The diameter of the flower is around one and a half inches.

Utilization Of Knock Out Roses In The Garden And Landscape

knock out roses

knock out roses

Knock Out roses have the potential to become the multi-talented infielders of your garden. They may be used as specimen plants, foundation plantings, border plants, or even as low hedges. It is also possible to plant them in containers. Due to the fact that they bloom continuously for nine months, they add color to the landscape even in the late summer when other flowers have stopped blooming.


Plant You may create a beautiful hedge that is covered in blossoms from spring through fall by planting Knock Out roses in a dense mass planting of the same color. You can use an explosion of bright roses to define the boundary of your garden, whether it be a driveway, a pathway, or both. Put some distance between them—at least three feet—so that they have room to develop into their full size and so that air may flow freely around them. When early spring arrives, go through and prune them to the desired height.

Laying The Groundwork

knock out roses

knock out roses

Use Knock Outs as foundation plantings around your home instead of the traditional boxwoods or other evergreen shrubs if you're looking for something a little bit different. You may expect your property to be surrounded by a thicket of roses for the better part of the year. The vibrant hues of the blooms will stand out against the dark houses. Place a row of small boxwoods in front of the Knock Out roses to define the edge of the bed. This will also provide a formal row of green to the soft mounds of multicolored roses in the bed.


You can plant Knock Outs in containers, which is a wonderful alternative if the majority of your yard is shaded because you can shift the container wherever the sun is. Put potted Knock Out roses in matching pots on either side of your front stairs, or put a single potted Knock Out on a sunny patio for a splash of color. Both of these options will give your home a welcoming and colorful appearance. Plant one of the two varieties of Knock Outs with a perfume — The Sunny Knock Out Rose or The White Knock Out — in pots and position them near your front door. This will ensure that you are greeted with a pleasant aroma whenever you enter or exit your home.

Mix them with fillers such as Artemisia, dianthus, coral bells, or bacopa and spillers such as licorice plant, Blue Star creeper, Calibrachoa, and sweet potato vine. Use them as the thriller plant in a thriller/spiller/filler container recipe.

Specimen Plant

Because some Knock Outs may grow to be as tall as 7 feet, they are ideal for use as single specimen plants in flower gardens because they provide height to the space. In the center of a circular bed, plant a Knock Out rose and then surround it with low-growing plants that form mounds. Alternately, you may put a Knock Out rose in a cottage garden alongside coneflowers, Shasta daisies, and delphinium to lend an air of formality to the space.


Because Knock Out roses are able to thrive in partial shade, they are an excellent choice for a naturalized border that connects a yard to a neighboring wooded area. They can also be put in the middle or back of a mixed, sunny border, where they will provide color in the late summer and early fall when other flowers have finished flowering for the year. This is because they bloom later in the season than other flowers.

Insects And Pets Diseases

Knock Out roses are renowned for their resistance to a wide variety of rose diseases and pests. They are, however, susceptible to the rose rosette, which is a virus that is transmitted by eriophyid mites that are carried in on the wind. When one of the tiny mites consumes a rose, it transmits the virus to the plant and, presto, your Knock Out becomes ill. After becoming infected, your rose, which was previously in good health, will start to produce clusters of new shoots that are bright crimson and seem... odd. These new stems flower, but the roses they produce are misshapen. As the rose rosette virus moves through the plant, it causes the plant to gradually wither away until it finally passes away.

Rose rosette, like other plant viruses, is difficult to contain because it moves through the plant from the inside out, infecting all of its parts. It is possible to salvage the rose by doing immediate and severe pruning on the brilliant red stems as soon as they develop, making sure to cut through the healthy green wood underneath. However, after the entire plant develops a rose rosette in its full glory, the plant will have completed its life cycle. Spraying won't work. To prevent it from infecting other plants, carefully pull the plant out by its roots, place it in a bag, and dispose of it in the trash rather than the composter.

They may also be plagued by Japanese beetles and rose slugs, which are also referred to as sawflies. However, roses are so resilient that they will continue to thrive even if insects feed on their leaves.