How to Care Knockout Roses – All you Need to Know

If you want to have one of the hardiest roses in your garden, then you should read this note about knockout roses. These roses can withstand temperatures as low as -25 °F (-32 °C), which makes them perfect for extreme climates. In this article, we will explain how to care for knockout roses to keep them beautiful in your garden.

These roses can thrive in partial shade and can thrive in only three hours of direct sunlight, they also tolerate drought, resist mildew and other diseases, which is why they are one of the hardiest roses.

As you can see, knockout roses are almost invincible, but they still need some care, which we will explain step by step in this guide.

Where to Plant Knockout Roses

For knockout roses to bloom to the maximum we must grow them in a place that has at least six hours of direct sunlight, and if they receive eight hours of sunlight per day even better. These roses can indeed grow with only three hours of light per day but if not, they will achieve an excellent bloom.

Knockout roses can grow up to 5 ft (1.5 m) tall. Keep in mind that they need space to grow properly, ideally in an area free of weeds and grass.

how to care knockout roses

Colors of Knockout Roses

Knockout roses can be found in various color ranges, some of which are listed below, all of which are resistant to various temperature ranges.


The color red is ideal for butterflies and hummingbirds, also red is the traditional color of Valentine’s Day. In this color, we find the rose “Knockout” (Rosa x “radrazz”) and “Double Knockout” (Rosa x “Radtko”).


In yellow we find the rose “Sunny Knockout” (Rosa x “Radsunny”). This color is widely used by landscapers to contrast with red and pink roses. It attracts butterflies, birds, bees, and some nocturnal pollinators such as moths.


In pink we find the rose “Blushing Knockout” (Rosa x “Radyod”) and “Pink Knockout” (Rosa x “Radcon”).  


It is also possible to find the rose “Rainbow Knockout” (Rosa x “Radcor”) in bicolor. It is bright pink on the outside but the central petals are more yellow.

white knockout roses

Type of Soil Required

Something very important to know how to take care of our knockout roses is the type of soil. Knockout roses need a pH of 6 to 6.5 for proper growth. It also needs to have very good drainage.

It is important that we measure the pH of our soil as with other pH ranges the rose could have difficulties in development.

For example, too high a pH could cause the rose to develop chlorosis, which would cause its leaves to turn yellow and not be able to photosynthesize properly.

Light and Climate for Knockout Roses

As mentioned above, it is best to place it in a spot in the garden where it receives at least six hours of direct sunlight.

Placing the knockout rose in full sun it will have an excellent development, in the partial shade it will grow slowly and with less showy flowers.

The best time to plant knockout roses is in late winter and early spring, this will give it time for its roots to develop properly before summer.

Watering Knockout Roses

When the knockout rose is young, we must give it abundant water, but without flooding its soil. Always water slowly to allow the water to be absorbed properly by the roots of the rose.

The knockout rose needs less water as it grows. When the rose is two years old or older and can withstand drought, water it once a week or twice a week in summer.

Never overwater because it will cause the leaves to turn yellow and then fall off. Pine bark helps conserve moisture, add some to your rose.

When to Fertilize Knockout Roses

When the knockout rose is a little over a year old then is the time to fertilize for the first time. Never fertilize in late summer as this is when the rose is preparing for dormancy and the coming winter months.

In the spring when new leaves begin to appear you can fertilize using a 5-10-5 or 4-8-4 rose fertilizer.

Too much fertilizer will cause the edges of the leaves to turn brown, on the other hand, too little fertilizer will cause the rose to develop more slowly and bloom less.

fertilize knockout roses

Pruning your Roses

In late winter or early spring, you should prune your knockout rose every year. When the rose is 3 to 4 feet (0.9 to 1.2 m) tall you can perform your first pruning. 

Remember to always disinfect your tools before pruning, not disinfecting your tools could cause the plant to get sick.  Always prune at a 45-degree angle.

Pruning your knockout rose will make it grow strong and healthy.

Pests and Diseases

If we want to know how to care knockout roses, we must learn to identify the possible pests and plagues of this beautiful rose.

Knockout roses are bred to be resistant to the most common rose diseases, but this does not mean they are invincible.

Two diseases that regularly affect roses are black spots and rust, which are caused by hot and humid conditions and are spread by water.

When watering you should avoid wetting the leaves to reduce the chances of contracting a fungal disease.

Where to Buy Knockout Roses?

Knockout roses are a registered trademark in case you didn’t know, that’s why the best place to buy these excellent roses is in their official online store. Here we leave you the best specimens so you should have them in your garden and you can take care of your knockout roses correctly.

Green Promise Farms Rosa `Sunny Knock Out` (Reblooming) Rose, 2 Size Container, yellow flower
Green Promise Farms Rosa `Sunny Knock Out` (Reblooming) Rose, 2 Size Container, yellow flower
For Best results, plant in used zones 4-8. Mature Height is 3-4ft, mature spread is 2-3ft.
Knock Out Roses - Rosa Knock Out (Rose) Rose, red flowers, #2 - Size Container
Knock Out Roses - Rosa Knock Out (Rose) Rose, red flowers, #2 - Size Container
For Best results, plant in used zones 4-8. Mature Height is 2-3ft, mature spread is 3-4ft.
$29.99 Amazon Prime
Green Promise Farms Rosa `Double Knock Out` (Reblooming) Rose, 2 Size Container, pink flower
Green Promise Farms Rosa `Double Knock Out` (Reblooming) Rose, 2 Size Container, pink flower
For Best results, plant in used zones 4-8. Mature Height is 3-4ft, mature spread is 3-4ft.

Fighting Knockout Roses Pests

Regularly check your knockout rose for pests such as aphids, bed bugs, spider mites, etc. Knockout roses are rarely bothered by these pests, but if you find these pests you should use neem oil or an organic insecticide. You can also remove diseased branches and leaves.

Mealybugs and scales can be removed with a fingernail or a cotton ball soaked in isopropyl alcohol.

We hope this article about how to care knockout roses will be of great help.

knockout rose pests
About Henry Morgan

We are the Morgans, Henry, and Julia, both agronomists from the University of Michigan, where we met. We are experts in putting our hands in the soil and developing organic foods and improving production processes for decades. Likewise, we have worked for companies such as Mondelez International, BASF, Monsanto, etc. currently in our role as science writers for as well as advisors in promoting large scale food growing in urbanized areas. In this website, we share what we are most passionate about, gardening and farming. Enjoy and see real photos on our website.