Roses have long been a popular plant because of their pleasant fragrance and romantic-looking blossoms. One variety that looks a lot like the classic rose but is much easier to grow and care for is the Double Knockout rose. This shrub rose variety is called a Double Knockout because it truly is a knockout flower! With its doubling petals and self-cleaning properties, it’s no wonder so many gardeners prefer growing the Double Knockout rose for fuller bloom.
If you want to learn more about how to grow and care for this type of rose, we have all the information you need to get started. Let’s take a closer look at this beautiful flower now...
Double Knockout Rose Overview
|Name||Double Knockout Rose|
|Hardiness zone||5 to 10|
|Fertilizer||Once a year in spring or late winter|
|Max growth||4 feet|
|Poisonous for||Not toxic|
|Light||Full sunlight up to 8 hours a day|
|Temperature||Heat and cold hardy, frost resistant|
|Soil||Natural and well-drained|
|Pests||Highly resistant to disease and pests|
|Favorite varieties||Sunny Knockout and Blushing Knockout|
Varieties of Double Knock Out Rose
- Double petals of up to 24 per flower
- Shrub roses that grow 3-4 feet wide
- Deep cherry red
- Black spot resistant
- Drought tolerant
- Flowers throughout the season
Pink Double Knockout Rose
- Moderately heat and cold tolerant
- Dark pink blossoms
- Up to 24 petals per flower
- Moderate to fast growth rate (30 inches per year)
Blushing Knockout Rose
- Grows to 4 feet tall
- Pink blooms
- Only requires 3 hours of sunlight a day
- Light fragrance
- Disease resistant
Sunny Knockout Rose
- Shrub roses
- Grow up to 5 feet tall
- Golden yellow buds turn creamy yellow after blooming
- Up to 7 petals per flower
- Disease resistant
Double Knockout Rose Care
Double Knockouts are extremely heat and drought tolerant plants. In fact, they can survive temperatures as low as -25 degrees fahrenheit and grow in a wide range of climates.
We all know the importance of watering plants. Giving any plant the correct amount of water will ensure it thrives. But be sure not to oversaturate the soil by checking its moisture every few days. If it’s dry to the touch, it’s time to water your rose.
Container-grown roses tend to dry out quicker than ground soil, so water them more often. Make sure the containers have enough drainage holes to prevent soggy soil.
As a rule of thumb, roses need weekly watering in the morning, and more often in periods of drought or heat. Never water your roses from overhead as the water droplets sitting on their leaves can encourage diseases.
Roses need up to 8 hours of sunlight per day. Some Double Knockout species require up to 5 hours of sunshine daily, so always plant your roses in full sun.
These roses thrive in well-drained, acidic soil that’s not oversaturated with water. To improve drainage, gather mulch around the base of the plant for better water absorption. That said, Double Knockouts are hardy, heat-tolerant plants that can grow in most soil types. However, they do prefer well-drained soils with 6-6.5 pH levels.
Just like all plants, Double Knockout roses will also benefit from regular feeding. Spread 3-6 inches of mulch layer around their bases as this will provide them with the necessary nutrients.
If your soil is lacking vital nutrients like nitrogen, potash or phosphate, you can buy a 10-10-10 fertilizer formula that’s specially for roses. Feed your plant in late winter or early spring every year after the final frost. You will soon notice the difference once your plant produces brighter and bigger blooms.
Double Knockout roses require moderate pruning throughout their lifespan. Since these plants are moderate to fast growers, they can reach up to 8 feet in height if left unpruned. This is not recommended as the flowers will look less healthy. Be sure to wait until the second season before pruning the roses as the first season pruning will be detrimental to their growth.
Prune the buds once they come out of dormancy in early spring. You can also cut back the shoots by as much as half to prevent the plant growing too tall. To encourage further blooms and improve the appearance of the flowers, deadhead them until 8-10 weeks before the first frost. This is the process of removing wilted blooms for a tidier appearance.
How to Plant & Progagate Knockout Rose
Why Grow Double Knockout?
The shrub size of the Double Knockout rose makes it ideal for planting in containers or ground. The showy blooms of this ornamental bush will make a beautiful landscape in any garden or porch. You can brighten up your backyard throughout spring, summer and fall with the richly-colored flowers of these captivating plants.
Double Knockout Rose Planting Step-by-Step
Step 1. Choose a location that receives the most sun. Remember, these roses require as much as 8 hours of sunlight a day. Their soil must be well-drained with adequate air circulation. Planting should be in fall or early spring after the danger of frost is passed.
Step 2. Dig a hole that’s as deep as the rose’s root ball. Gently loosen the plant’s roots and spread them out if necessary.
Step 3. Place the rose plant in the dug up hole and adjust its height by adding more soil. The swelling part of the plant called the bud union should remain 1 or 2 inches above the soil level.
Step 4. Make sure the plant is securely in place and water deeply.
Step 5. Press down the soil firmly to eliminate air pockets and water again to settle the soil.
Step 6. Spread 2-3 inches of organic mulch layer around the base of the plant to retain moisture and prevent weeds.
Tip: if planting multiple rose bushes, space them 3 feet apart.
Caution: do not add lime or sulfur to the soil as these can injure the plant.
Propagating Double Knockout Rose Step-by-Step
Taking clippings and transforming them into a new rose plant will yield results within just a couple of weeks. This is by far the quickest way to grow young plants. Follow these steps to learn how to propagate a Double Knockout rose:
Step 1. Obtain a 6-8 inch long clipping by cutting the rose’s tip at a 45-degree angle.
Step 2. Remove the flowers and leaves but leave the top-most leaves intact.
Step 3. Place the cutting in a rooting hormone before potting it in soil.
Step 4. Cover the pot with a plastic bag and keep it outside in indirect sunlight.
Step 5. Lightly spray the soil to keep it damp.
Step 6. Once the roots start showing, transfer the plant to its desired location.
Step 7. When planting in the ground, leave at least 3 feet of space between the propagated cutting and the other plants to allow for proper growth.
Experienced gardeners recommend planting the Double Knockout in the dormant months between December and February for optimum results.
Growing Double Knockout in Containers
Now that you’ve learned how to propagate your roses, you can start growing them in containers. Growing roses in pots is an easy and low-maintenance way of enjoying their blooms.
The best thing about these shrubs is that anyone can grow them thanks to their hardy and pest resistant qualities. These rose varieties are the perfect size for pot growing and don’t need a huge container. In fact, a 10-15 gallon container will suffice. Just make sure the container has good drainage and add two inches of gravel to the bottom. Gravel will help keep the pot stable as well as provide good drainage.
Follow these simple steps to grow your Double Knockout in a container:
Step 1. Fill half of the pot with some potting soil and place the root ball in the soil. Make sure you loosen the roots to prevent them from tangling before adding the rest of the soil to the pot.
Step 2. Never overfill the crown of the rose with too much soil as this can suffocate its roots. The crown of the rose is the point where the stems start. Note: plant the rose at about the same height as it was in the nursery pot.
Step 3. Add 1 inch of mulch layer but be sure to keep the crown uncovered for air circulation.
Step 4. Water the potted plant thoroughly and place it in a sunny area close to a window.
Other Quick Growing & Care Tips for Double Knockout
While all species of Knockout roses are easy to grow and don’t require much maintenance, there are still some steps you can take to ensure healthy blooms. Take note of the following care tips to increase your plant’s appearance:
- Start pruning from early spring to help get the best out of your rose bushes.
- If you haven’t chosen a location to plant your rose bush yet, consider the amount of sunlight it needs to receive. Partial shade will not help your plant so light is the most important requirement for healthy bushes.
- Before planting, add organic compost or manure to the soil as well as some rose fertilizer if possible.
- When feeding your roses, use good quality chemical or organic granular fertilizer in early spring to get them off to a good start. To ensure they are well-fed and blooming, you can continue feeding them up until late fall.
Common Diseases and Pests
The Double Knockout rose is highly resistant to garden pests and diseases including black spot and mildew. In fact, all knockout varieties are immune to pest attack, thus making them ideal for growing outdoors.
When is the best time to prune my Double Knockout roses?
Prune your Double Knockouts as soon as their buds come out of dormancy. The best time to prune is in late winter or early spring as soon as the plant prepares for the next growing season and the final frost has passed. Having said that, you can still prune your Double Knockouts even if new growth has already started.
Why are my Double Knockouts not flowering?
It may be due to the roses not getting adequate direct sunlight. Keep in mind that roses need up to 8 hours of sunlight a day in order to bloom. If there are trees nearby, they will prevent light reaching the rose shrubs. Another reason could be lack of fertilizer in the soil. Test your soil using a home test kit to find out which nutrients it is lacking. The best rose fertilizers have a formula of 10-10-10, which are balanced in vital nutrients.
What to do when my roses are yellowing?
Roses that turn yellow may be due to the soil’s pH levels being too high or lacking in iron. Overwatering can also cause the plant to turn yellow. Roses don’t like too much water around their roots.
How long do Double Knockout roses last?
Double Knockouts usually bloom every 6 weeks. To help them continue producing blooms throughout their entire season, it takes a little time for correct care. If deadheaded, your roses will produce blooms every 6 weeks from mid-spring to fall.
How do I care for my Double Knockouts in winter?
If grown in the ground, add 2-3 inches of mulch layer, which can include leaves, grass clippings and pine bark around the base of the roses. This will help protect the plant through winter by insulating its surrounding soil. To prevent wind from drying out the plant, wrap it with burlap during winter.
Double Knockout roses are the easiest flowers to grow and care for. These self-maintaining, fragrant shrub plants bloom for months and provide a beautiful backdrop in the garden. No matter your gardening skills, simply follow our basic growing tips in this article and you’ll no doubt receive even more blooms that are brighter and bigger.
Let us know how you progress with your Double Knockout rose bush by leaving your comments below!