How to Grow and Care for Knockout Roses

Knockout roses are among the most eye catching flowers available. As the name suggests the roses abundant flowering habit, colorful blooms and distinctive fragrance makes it a knockout addition to any garden. The hardy nature of the knockout rose, meaning that it will grow in many different situations such as adding structure to a butterfly garden, has also contributed to its popularity. You can even try turning the blooms into rose water or rose oil.

Knockouts are an increasingly popular garden flower. Hardier than other roses and less prone to disease they retain the original roses’ color and fragrance. 

A fantastic addition to any flower garden. This guide will explain everything you need to know about knockout roses,  including how to grow and care for them.

 What are Knockout Roses?

Knockouts were developed in 1989 by Will Radler, a rose enthusiast from Milwaukee. Radler was aiming to create a rose that was not only fragrant and colorful but also easy to care for and hardier than other varieties. After many years of development, the result was the knockout rose.

In 1992 Radler entered into an agreement with the Star Roses and Plants company. The Philadelphia based company continued to develop the rose, this time with the aim of making it commercially available. 8 years later a patent was granted and knockout roses were launched.

They were an instant hit. In the same year the knockout rose was named winner of the All American Rose Selections.

Radler set out with the aim of improving the classic rose. Making it easier to care for and more disease resistant. The result, knockout roses, are a versatile addition to any flower garden. 

In many respects knockouts resemble many other types of rose. However there is one significant difference. The scent of the knockout rose is far lighter and sweeter than the classic rose fragrance.

While knockout roses are a popular addition to any garden there are a few downsides. Knockouts don’t last for long when cut and placed in water. This means that they are not a good choice for cut floral displays. This, however, hasn’t noticeably affected the popularity of these colorfully abundant flowering plants.

Varieties of Knockout Rose

Still a relative newcomer to the market there are fewer varieties of knockout roses available compared to other roses. However there is still plenty of choice on offer.

The rich color of knockout roses is one of the plant’s main attractions. If cared for properly, and special care is taken not to wet the petals when watering, the colors only become richer and more intense.  

Some of the most popular knockout roses are:

Rose Radrazz, the original knockout rose. A reliable variety it produces single blossoms in various shades of red.

Rosa Radcon, also known as the Pink Knockout Rose. As the name suggests it produces single, light pink flowers.

Rosa Radyod or Blushing Knockout. Radyod produces delicate, single, pale pink flowers.

Rosa Radcor, sometimes called the Rainbow Knockout, this variety produces attractive small, single flowers that are pink in color with yellow centres.

Rosa Radsunny, or Sunny Knockout, produces sweet smelling yellow flowers.

Rosa Radtko is a double flower rose. Radtkos cherry red flowers are more tolerant of the cold than other varieties.

Rosa Radtkopink, another double flower, this variety produces bright pink blooms.

Rosa Radwin, is a climbing variety. Capable of reaching 12ft if grown in full sun. In the fall the plants foliage darkens to a seep shade of burgundy, complementing the rich red flowers.

Growing Knockout Roses

As we have already noted knockouts are easy to care for. They are also hardier than other roses. This doesn’t mean that they don’t require some special care and attention however. When cared for correctly knockouts produce copious colorful flowers throughout the summer months.

The first thing that you will need to get right is the positioning and planting of your knockout roses.

Positioning Knockout Roses

Knockout roses thrive in USDA zones 7-11. Gardeners outside these zones can also successfully grow the roses. However they will require a little extra care. Their flowering habit may also not be as abundant.

Knockouts do best in bright sunny locations, receiving 6-8 hours of sunlight every day. The ideal position will allow the roses to enjoy the sun during the morning before providing some shade during the hottest part of the afternoon. Knockout roses will also grow in partial shade positions, but the growth may be slower and the flowering not as abundant.

Soil Conditions

Your soil should be well draining. Overly sand or heavy clay soils negatively affect drainage. If you are not careful this can lead to the roots of the plant rotting.

Before planting, work in organic matter, such as compost. This will help to improve the soil. Other ways of improving the soil include adopting a no dig approach.

Knockout roses like rich, well draining soil. You should work the soil over, loosening it up and removing any weeds before you begin planting. If your soil is poor working in compost or other organic matter will help to enrich and improve it.

Planting Knockout Roses

The best time to plant knockouts is when they are dormant. This means either planting either early in the spring or in the fall. Planting when the roses are dormant allows the roots of the plant time to become established before the plant begins to flower.

To plant knockout rose dig a hole in the soil large enough to contain the root ball of the plant. When you place the root ball in the hole it should sit just below the surface.

You may also want to place a stake or some form of support in the hole. This will help the knockout rose to maintain a good upward growth habit. It will also make pruning and tidying the plant easier.

When you are happy, backfill the hole with soil and firm it down. Be careful not to compact the soil. Water in well.

Caring for Knockout Roses

Once planted the roses will require some additional care and attention. This will help them to keep healthy. It will also help to nurture the knockouts famed flowering habit.

Watering

While roses require regular watering, knockouts are not particularly thirsty. Aim to keep the soil around the plant moist. In good soil and ordinary conditions this means watering once a week. During hot periods you will need to water the plants more regularly. Checking the soil once a day will help you to gauge whether watering is required. If top inch of the soil has dried out, the plants may require watering.

Water your flowers regularly. The soil around them should be evenly moist. However, try not to get the leaves wet. Damp leaves, particularly during the cooler evening and night, can become a breeding ground for disease. 

Mulching the base of plants helps to conserve moisture. It also helps to keep the soil cool, meaning plants are less likely to wilt in warm weather.

If you are growing your roses in containers remember that they will require more regular watering than those grown in the soil.

As you water the plants try to keep the leaves dry. This is particularly important if you are watering later in the day. Damp leaves and cool conditions are a breeding ground for disease. Water allowed to dry on the petals of the plant can also wash the color for the flower.

Aim to water just the base of the plant. This also ensures that the plant gets more of the moisture. Watering early in the day allows the plants time to dry in the sun before the temperatures fall.

Don’t overwater your roses. This can encourage disease. Plant roots may also rot in wet soil.

To cut down on your water usage try installing a water but. This will allow you to harvest rainwater that you can then reuse in the garden.

Feeding

Knockout roses growing in rich soil will not require feeding.

During their first spring apply a dose of good quality rose feed. This will help the plants to establish themselves. It will also encourage flowering.

If positioned correctly in good soil feeding knockout roses isn’t necessary. However, an occasional dose of rose feed will encourage the plants to flower. This can be particularly beneficial during the plants first year.

You can also apply regular doses of foliar feed. This will encourage flowers to form. An epsom salt solution will also encourage flowering. If you really want to cut down on your chemical usage, try making your own plant feed.

Pruning

Knockout roses are not only disease resistant they are also self-cleaning. This means that you do not need to deadhead them. The newly emerging flowers will simply push spent, older flowers out of the way. For the most part the plants will also naturally maintain their compact, upright shape.

While pruning isn’t necessary, it will help to keep the roses neat and nice to look at. It will also help to prevent Rose Rosette Disease. Knockout roses are known for being resistant to the majority of common rose problems and diseases. However they can fall victim to Rose rosette disease. This is particularly troublesome in mass plantings of the flower.

Should you notice any possible signs of disease prune as quickly as possible. Taking prompt action prevents disease from spreading to the rest of the plant and to other flowers.

Pruning roses, back in the fall will encourage vigorous new growth to emerge the following spring. This will also lead to a more abundant floral display.

Winter Care

Knockout roses are hardy in USDA zones 9-11 they are quite hardy. In colder zones you will need to take protective action before the winter temperatures hit. Exposure to low temperatures can damage your roses. This can form part of your gardens annual fall transition routine.

To protect the plants from cold spells and severe frosts, cover the plants with a horticultural fleece or protective covering. This protects the leaves and stems. Mulching the bases of the plants, or simply covering with thick layers of straw or leaves, will insulate the base and root system. You can also use homemade compost to mulch the base of plants.

A small mini greenhouse is a useful way of covering permanently sited plants. This ensures that they are protected from cold periods and frosts. They are also a great way of trapping heat, meaning that the soil doesn’t get too cold.  

If you choose not to cover the roses, you will need to regularly clear them of snow and ice. This prevents the stems from freezing and snapping.

Container grown plants can be taken undercover in the fall. As spring temperatures begin to rise you can return the containers to their usual position.

Easy to grow and maintain knockouts are an eye pleasing addition to the garden. Their hardy nature means that they are an option for any gardener regardless of their climate or situation.

Easy to care for and surprisingly hardy knockout roses are an attractive and fragrant addition to almost any garden. Whether you are an experienced gardener or relatively new to the hobby the knockout rose is a rewarding place to begin.

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