How To Grow And Care For 'Knock Out' Roses

As one of the longest-blooming roses, the Knock Out® rose series (Rosa 'Knock Out') is an excellent option for a low-maintenance flower. Relatively pest-and-disease-resistant, the Knock Out® rose continuously features one-and-a-half inch in diameter flowers in coral, yellow, pink, blush, red, orange, and white varieties. The attractive flowers are available in single or double forms with glossy, dark green foliage. The Knock Out® rose is a shrub that grows up to six feet tall and can spread four feet wide. Enjoy season-long blooms with this compact rose plant. 

Plant Attributes

Knock Out® Rose Care

Knock Out® roses are relatively easier to maintain than other roses. It's a tough rose, grows in almost any well-drained soil in a sunny spot, and is more resistant to black spot fungus than many other cultivars—a common affliction for roses.

Knock Out® roses may start small and compact, but they will only stay that way for a while. These plants continue to grow bigger and bigger every year. However, if you garden in a small space, you can grow they new miniature variety of Knock Out, 'Petite'. Since Knock Out® blooms on new growth, you can prune it at any time of year. Be sure to wear leather gloves, though, as it's one of the most viciously thorny plants you'll find. You can cut it down to a foot tall if you want. In response, it'll send out lots of new growth and blooms.

Light

These roses grow best in full sun, at least six hours daily. The more sun it receives, it will experience more frequent blooms and be showier. Avoid diseases, like powdery mildew, by providing plants with morning sun and filtered or partial afternoon shade.

Soil

Average soil with a slightly acidic to neutral pH is best for these plants. Add organic compost or mulch to maintain soil conditions, including adding nitrogen as a supplement.

Water

Younger plants need more consistent watering than established roses when it becomes relatively drought-resistant. Water the roots in the morning to prevent leaves from developing a fungus from wet foliage. Plants will also need more regular watering during the growing season.

Temperature and Humidity 

Knock Out® roses are cold-hardy and heat tolerant. These flowers can withstand temperatures down to 10°F and periods of frost before going dormant. In colder climates, help insulate the plant's roots by adding a layer of organic mulch, such as straw, near the base. If grown in containers, add a protected wrap around the plant to protect it from frost.

Fertilizer

These roses benefit from a rose-specific or balanced fertilizer every month, or every other month, during the growing season. Prepare plants for winter by stopping fertilizing in late summer. 

Types of Knock Out® Roses

The popularity of the Knock Out rose encouraged several cultivar varieties. Selections are typically trademarked, so consider purchasing one of these varieties for your garden: 

• 'Sunny' Knock Out: A shrub with yellow-to-cream flowers and dark green, semi-glossy foliage. 
• 'Orange Glow' Knock Out: This slightly fragrant variety features orange blooms infused with shades of coral, yellow, and pink, paired with green foliage. 
• 'Peachy' Knock Out: This medium-sized flower has pink petals and a yellow center with deep green, semi-glossy foliage. 
• 'Easy Bee-zy™' Knock Out: Light, citrus-scented shrub with yellow flowers and green foliage. 
• 'Blushing' Knock Out: A light pink-petaled flower with medium-sized flowers paired with mossy green foliage tinted with blue hues. 

Pruning

Prune these roses in the late winter or early spring when new growth emerges. Trimming the shrub back two-thirds every few years will help maintain the plant's shape. It is unnecessary to deadhead the flowers but to keep the plant healthy while blooming continuously, groom the branches by clipping off the faded flowers. If you leave them, they'll form rose hips with seeds inside, and flowering will slow to a crawl. Grooming the Knock Out rose every week or so spurs new growth loaded with new rose buds.

Propagating

The Knock Out® rose is protected from propagation as a trademarked cultivar. Growing these flowers from seed or other propagation methods is a copyright infringement, so it's always best to purchase these roses directly from a verified seller. 

Potting and Repotting

Repot Knock Out roses every two to three years as they will outgrow their container. When transplanting roses, select a container with good drainage at least two times larger than the current pot so the plant has room to expand. In the spring, gently remove the rose from the older container and shake off any excess dirt. Add the root ball to a new container filled with fresh potting soil. Plant the rose so the top of the rootball is flush with the top of the soil. Water often while the roots establish, checking the soil daily in extremely hot weather. In colder climates, move roses to a warm location in the winter, so the roots do not freeze. 

Overwintering

The winter care will vary depending on where you are growing Knock Out® roses. Add a two-to-three-inch layer of organic mulch when growing in the ground. Use leaves, pine, or straw to protect the plant's roots and help insulate it throughout the winter. Adding a burlap covering around the plant can also help protect the plant from harsh weather conditions. When growing roses in containers, leave the plant outdoors for the season's first frost to help it adjust to dormancy. Then, place the containers in a cool, dark area for the remainder of the winter. Continue caring for roses, ensuring it does not completely dry out. 

Common Pests & Plant Diseases

Just because Knock Out is more disease resistant than some other roses, it doesn't mean you don't occasionally have other issues to address. In hot, dry weather, tiny spider mites on the undersides of the leaves may suck out the sap, causing the leaves to look speckled or bronzed. Then you'll need to spray with horticultural oil or insecticidal soap. Spraying the foliage with a jet of water also works because spider mites love dry foliage and hate wet foliage.

Another common problem is leaves dotted with small holes. The culprit is a sawfly that lays tiny eggs on the undersides of the leaves. The eggs hatch into larvae called rose slugs that chew away at the leaves from the undersides, leaving little "windows" and holes. Spraying the leaf undersides with neem oil will control this. Neem oil also works against another insect pest that likes to eat the Knock Out rose, the Japanese beetle. Just don't spray the flowers, as neem is toxic to bees. Make sure to spray early in the morning before bees are present.

How to Get Knock Out Roses to Bloom 

It is not necessary to deadhead flowers to encourage new growth, but maintaining proper care, such as plenty of sunlight, moist soil, and adequate fertilization, will help protect the plant's flowers and foliage.

Common Problems

Despite being relatively disease-and-pest-resistant, there are still some issues when growing and caring for Knock Out'roses.

Curling Leaves

Rose diseases, such as powdery mildew, rust, and occasionally black spot, can impact these roses. Still, rose rosette is a virus that spreads from the eriophyid mite and can cause contorted stems and leaves. Knock Out roses are susceptible to this virus. The only way to treat it is by digging up the plant and removing the diseased plant.

Holes In Foliage

'Knock Out' roses are susceptible to Japanese beetle attacks, but if you notice holes in the foliage, other pests such as rose slugs or sawflies might be on the underside. Protect plant foliage by using neem oil or insecticidal soap.