Simply Trees

White Knock Out® Rose Bush

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Twice a monthFull sunSpring to fall
  • Crisp White Blooms: Features bright white flowers that bloom continuously, refreshing the garden landscape through multiple seasons.
  • Disease Resistance: Exhibits strong resistance to common rose diseases, including black spot and powdery mildew, ensuring a healthy and vibrant display.
  • Low Maintenance: Requires minimal care, with no need for deadheading to encourage reblooming, making it ideal for those seeking beauty without the fuss.

More Details

The White Knock Out® Rose Bush, officially known as ‘Radwhite’ PP 20,273, is part of the renowned Knock Out® rose series, celebrated for its disease resistance, continuous bloom cycle, and maintenance ease. This variety stands out with its crisp white flowers that provide a stunning contrast against the dark green, glossy foliage. Blooming from early spring until the first frost, it offers a long season of interest in any garden setting. The White Knock Out® Rose is compact and bushy, making it an excellent choice for borders, mass plantings, or as a striking standalone specimen. Its self-cleaning flowers and exceptional hardiness make it a favorite among both novice and experienced gardeners looking to add reliable beauty to their outdoor spaces.

Growth rate: Moderate growth rate; mature height of 3-4 feet and width of 3-4 feet.

Please note: Images on our website depict plants and trees at full maturity to showcase their expected grown characteristics. These images are illustrative examples only and do not represent the size of plants or trees upon delivery.

Pruning: Prune in early spring to shape the bush and remove any dead or damaged wood. Light pruning throughout the season can help maintain its compact form.

Fertilization: Apply a balanced, slow-release fertilizer formulated for roses in early spring to encourage healthy growth and abundant flowering.

Winter Protection: In colder zones, applying mulch around the base can help protect the roots during winter.


Select a location with full sun and well-draining soil. Dig a hole as deep and twice as wide as the root ball. Plant the rose bush, backfill with soil, and water thoroughly. Space plants 3-4 feet apart to allow for mature spread and air circulation.

Requires regular watering during its establishment phase and thrives in full sun, making it a low-maintenance choice for adding elegant white blooms to the garden. Once established, it is drought-tolerant, requiring only occasional watering.

We process and ship your order as quickly as possible, typically within 1-3 business days. You will receive a shipping confirmation with tracking information once your item(s) ship.

We have perfected packaging and shipping plants & trees! That is why we DO NOT use any third-party fulfillment like most other online retailers. Your trees go straight from our farm to your door, safely packaged by our team of seasoned professionals. Our process ensures your plants leave our facility and arrive to your door in the best condition possible!

In cases of extreme cold or hot weather, we may temporarily delay shipping to ensure the well-being of your plants. Our primary focus is on delivering healthy and thriving plants to you. Rest assured, we'll make every effort to notify you of any delays promptly.

Please allow additional ship times during inclement weather and sale periods. We do not process or ship orders on the weekend or U.S. Holidays. Simply Trees is not responsible for delays due to carriers, local disruptions, or weather.

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At Simply Trees, we're committed to your satisfaction. If your plants arrive considerably damaged or sustained damage beyond the point of recovery, please contact us within five days at sales@simplytrees.store with clear photos for assistance. Our 30-day guarantee covers issues after planting, subject to our terms and conditions. We can't cover plants in the wrong climate or with inadequate care, but we're here to help in other situations. For a detailed understanding of our 30-day guarantee and how we ensure a fair process, click here to learn more.

USDA GROW ZONE:

Zones 5-11

The White Knock Out® Rose Bush thrives in USDA Zones 5-11, adapting well to a variety of soil conditions, as long as they are well-drained. It prefers full sun to produce the most prolific blooms and maintain its disease resistance. Its versatility and durability make it suitable for various landscape applications, from residential gardens to public spaces.

Frequently Asked Questions

The White Knock Out Rose bush typically reaches a mature size of approximately 3 to 4 feet in height and spread. This compact and rounded growth habit makes it an excellent choice for various garden settings, including borders, mixed beds, and containers.

While individual growth characteristics may vary slightly depending on factors such as climate, soil conditions, and care provided, White Knock Out Rose bushes generally maintain a relatively uniform size and shape. They produce dense foliage and abundant blooms throughout the growing season, creating a stunning display of white flowers against dark green foliage.

Proper care, including adequate sunlight, water, and nutrients, as well as regular pruning and maintenance, can help ensure that your White Knock Out Rose bush reaches its full potential and remains healthy and vibrant in your garden landscape. By providing optimal growing conditions and allowing sufficient space for the bush to spread, you can enjoy the beauty of its blooms and foliage for many seasons to come.

The growth rate of a White Knock Out Rose bush can vary depending on factors such as climate, soil conditions, and care provided. However, here's a general overview of the growth rate you can expect from a White Knock Out Rose bush:

Establishment Phase: In the first year after planting, a White Knock Out Rose bush typically focuses on establishing its root system and may exhibit moderate growth above ground. During this initial phase, it's essential to provide regular watering and proper care to encourage healthy root development and establish a strong foundation for future growth.

Subsequent Years: Once established, a White Knock Out Rose bush tends to grow more vigorously, producing new shoots and branches each year. Under optimal growing conditions, it can grow approximately 1 to 2 feet in height and spread per year. However, growth rates may vary depending on factors such as pruning, fertilization, and environmental conditions.

Continuous Growth: A White Knock Out Rose bush exhibits continuous growth throughout the growing season, especially during periods of active growth in spring and early summer. With proper care, including adequate sunlight, water, and nutrients, as well as regular pruning and maintenance, you can encourage healthy, vigorous growth from your bush.

Pruning Influence: Pruning practices can influence the growth rate of a White Knock Out Rose bush. Proper pruning techniques, including removing dead or diseased branches and shaping the bush's canopy, can help maintain its size and shape and promote healthy growth.

Mature Size: The ultimate size of a White Knock Out Rose bush depends on various factors, including its specific cultivar, growing conditions, and maintenance practices. On average, mature White Knock Out Rose bushes can reach a height and spread of 3 to 4 feet, forming a compact and rounded shape.

Overall, a White Knock Out Rose bush is valued not only for its beautiful white blooms but also for its relatively fast growth rate and ability to fill in garden spaces with lush foliage and flowers. With proper care and attention, you can enjoy steady growth and abundant blooms from your White Knockout Rose bush, enhancing the beauty of your garden landscape.

When selecting a planting location for your Knock Out Rose bush, consider the following factors to ensure optimal growth and blooming:

Sunlight: Choose a planting site that receives full sunlight for at least 6-8 hours per day. Knock Out Rose bushes thrive in sunny locations and require ample sunlight to produce abundant blooms. Avoid planting them in shaded areas where they may not receive sufficient sunlight, as this can lead to reduced flowering.

Soil Drainage: Ensure that the planting site has well-draining soil to prevent waterlogging, which can cause root rot and other moisture-related issues. Knock Out Rose bushes prefer soil that is rich in organic matter and has good drainage. If the soil is heavy or clay-like, consider amending it with compost or other organic matter to improve drainage.

Air Circulation: Choose a location with good air circulation to help prevent foliar diseases, such as powdery mildew and black spot. Adequate air movement around the bushes helps dry foliage quickly after rainfall or irrigation, reducing the risk of disease development.

Space: Knock Out Rose bushes have a compact growth habit but still require enough space to grow and spread. Plant your bush in a location where it has room to reach its mature size without being crowded by other plants or structures. Space multiple bushes at least 3-4 feet apart to allow for adequate air circulation and room for growth.

Accessibility: Consider accessibility when choosing a planting location for your Knock Out Rose bush. Plant it in an area where you can easily access it for watering, pruning, and maintenance tasks. Avoid planting it too close to obstacles or in hard-to-reach areas of your garden.

Aesthetics: Lastly, consider the overall aesthetic of your landscape when selecting a planting location for your Knock Out Rose bush. Choose a spot where the bush's beautiful blooms can be showcased and appreciated, either as a focal point or as part of a mixed border or garden bed.

By considering these factors and choosing a suitable planting location, you can ensure that your Knock Out Rose bush thrives and produces abundant blooms, enhancing the beauty of your garden landscape.

Caring for Knock Out Rose bushes involves providing proper maintenance and attention to ensure their health, vigor, and abundant blooming. Here's a comprehensive guide on how to care for your Knock Out Rose bushes:

Sunlight: Plant your Knock Out Rose bushes in a location that receives full sunlight for at least 6-8 hours per day. Adequate sunlight is essential for promoting vigorous growth and abundant blooming. If possible, choose a site with morning sun exposure to help dry dew off the leaves, which can reduce the risk of foliar diseases.

Watering: Water your Knock Out Rose bushes deeply and consistently, especially during the hot summer months. Provide enough water to keep the soil evenly moist but not waterlogged. Avoid overhead watering to prevent foliar diseases, and water at the base of the bushes to deliver moisture directly to the roots.

Fertilizing: Apply a balanced fertilizer formulated for roses in early spring, just as new growth begins. Follow the manufacturer's instructions for application rates and timing. Additionally, you can supplement with additional feedings throughout the growing season to support continuous blooming.

Pruning: Prune your Knock Out Rose bushes lightly in late winter or early spring to remove dead, diseased, or damaged branches. Shape the bushes as desired, but avoid heavy pruning during the growing season, as this can remove flower buds and reduce blooming. Deadhead spent flowers regularly to encourage continuous blooming.

Mulching: Apply a layer of organic mulch, such as shredded bark or compost, around the base of the Knock Out Rose bushes. Mulch helps retain soil moisture, suppress weeds, and regulate soil temperature. Keep the mulch a few inches away from the stems to prevent rot.

Disease and Pest Control: Monitor your Knock Out Rose bushes regularly for signs of pests, such as aphids or spider mites, and diseases like powdery mildew or black spot. Treat any issues promptly with appropriate organic or chemical controls to prevent them from spreading.

Winter Protection: Provide winter protection for your Knock Out Rose bushes in colder climates. Mulch around the base of the bushes to insulate the roots, and consider wrapping the stems with burlap to protect them from temperature fluctuations and frost cracks.

Support: Depending on the growth habit of your Knock Out Rose bushes and local weather conditions, you may need to provide support, such as staking or tying, to help the bushes withstand strong winds or heavy flower clusters.

By following these care guidelines, you can ensure that your Knock Out Rose bushes remain healthy, vibrant, and blooming throughout the growing season, enhancing the beauty of your garden landscape.

Knock Out Rose bushes have a relatively compact growth habit and do not spread aggressively like some other types of plants. However, they can gradually increase in size over time through the development of new shoots and branches. Here's a closer look at how Knock Out Rose bushes spread:

Clumping Growth: Knock Out Rose bushes typically grow in clumps, with new shoots emerging from the base of the plant and gradually expanding outward. While they may increase in size over the years, they tend to maintain a relatively contained growth habit, especially when compared to spreading or invasive plants.

Limited Spread: Unlike some groundcover plants or invasive species, Knock Out Rose bushes do not spread rapidly or aggressively through runners or rhizomes. Instead, their spread is primarily achieved through the growth of new stems and branches from the existing plant.

Maintenance Practices: Proper pruning and maintenance can help control the spread of Knock Out Rose bushes and maintain their desired size and shape. Regular pruning removes old, woody growth and encourages the development of new, vigorous stems, which can help prevent the bushes from becoming overly dense or sprawling.

Spacing Considerations: When planting Knock Out Rose bushes in the landscape, be mindful of spacing to prevent overcrowding and ensure adequate air circulation. Space the bushes according to their mature size, typically 3-4 feet apart, to allow room for growth and minimize the need for excessive pruning.

Containment: If you have concerns about the spread of Knock Out Rose bushes, you can install physical barriers, such as edging or root barriers, to help contain their growth and prevent them from encroaching on adjacent areas of the garden.

Overall, while Knock Out Rose bushes can gradually increase in size through the growth of new shoots and branches, they do not spread aggressively like some other plants. With proper care and maintenance, you can enjoy the beauty of Knock Out Rose bushes in your landscape without worrying about them becoming invasive or overly expansive.

Knock Out Rose bushes are prized for their prolific and continuous blooming throughout the growing season. Here's a summary of how often you can expect Knock Out Rose bushes to bloom:

Continuous Blooming: One of the key features of Knock Out Rose bushes is their ability to produce flowers continuously throughout the growing season. Unlike traditional roses that have distinct flowering periods, Knock Out Roses can bloom repeatedly from spring until the first frost in fall.

Frequency of Blooming: Under optimal growing conditions and with proper care, you can expect Knock Out Rose bushes to bloom every 5 to 6 weeks throughout the growing season. Individual flowers typically last for several days to a week before fading, but the bushes continue to produce new blooms to replace them.

Abundant Flowering: Knock Out Rose bushes are renowned for their high bud count and prolific blooming. Each bush can produce hundreds to thousands of flowers over the course of the growing season, creating a spectacular floral display that adds color and beauty to the landscape.

Response to Pruning: Regular pruning and deadheading (removing spent flowers) can help promote continuous blooming in Knock Out Rose bushes. Pruning encourages the development of new flowering stems and removes old, spent blooms, allowing the bushes to redirect energy into producing new flowers.

Environmental Factors: Environmental factors such as sunlight, temperature, and moisture levels can influence the frequency of blooming in Knock Out Rose bushes. Providing optimal growing conditions, including full sunlight, adequate water, and regular fertilization, can help maximize blooming throughout the season.

Overall, Knock Out Rose bushes are prized for their reliable and continuous blooming, making them a popular choice for gardeners looking to add color and beauty to their landscapes. With proper care and attention, you can enjoy a stunning display of flowers from your Knock Out Rose bushes throughout the growing season.

Pruning practices for Knock Out Roses can vary depending on factors such as climate, growth habit, and individual preferences. Here are some considerations regarding whether to cut back Knock Out Roses in the fall:

Fall Pruning: In general, it is not recommended to perform extensive pruning on Knock Out Roses in the fall, especially if you live in a region with cold winters. Fall pruning can stimulate new growth, which may be more susceptible to frost damage as temperatures drop. Additionally, pruning in the fall can remove protective foliage and leave the plants vulnerable to winter stresses.

Spring Pruning: The ideal time to prune Knock Out Roses is in late winter to early spring, just before new growth begins. This timing allows you to remove any dead, diseased, or damaged branches, as well as shape the plants for the upcoming growing season. Pruning in spring also minimizes the risk of frost damage to newly pruned branches.

Maintenance Pruning: Throughout the growing season, you may need to perform light maintenance pruning on your Knock Out Roses to remove spent flowers, control size, and shape the plants. These minor pruning tasks can be done as needed to maintain the plants' health and appearance.

Winterization: While fall is not the time for extensive pruning, you can still prepare your Knock Out Roses for winter by removing any dead or diseased wood and ensuring the plants are adequately hydrated. Mulching around the base of the plants and protecting the stems from temperature fluctuations can also help winterize the plants and promote their health during the dormant season.

Pruning Influence: Proper pruning techniques can help maintain the size and shape of Knock Out Roses and encourage healthy growth and abundant blooming. When pruning, focus on removing dead, diseased, or damaged branches, as well as shaping the plants to promote good airflow and light penetration.

In summary, while some light maintenance pruning may be performed on Knock Out Roses in the fall to remove dead or diseased wood, extensive pruning should be avoided at this time. Save more significant pruning for late winter or early spring to minimize the risk of winter damage and promote healthy growth and blooming in the coming season.

The frequency of watering Knock Out Roses depends on several factors, including weather conditions, soil type, and the age of the plants. Here are some general guidelines for watering Knock Out Roses:

Establishment Period: Newly planted Knock Out Roses require regular watering to establish their root systems. Water the plants deeply immediately after planting, and continue to water them regularly for the first few weeks or months until they become established. Provide enough water to keep the soil consistently moist but not waterlogged.

Weather Conditions: Adjust your watering schedule based on weather conditions. During hot and dry periods, Knock Out Roses may require more frequent watering to prevent drought stress. Conversely, reduce watering during cool and rainy weather to avoid waterlogging the soil.

Soil Moisture: Monitor the moisture level of the soil around the Knock Out Roses regularly. Check the soil moisture by inserting your finger into the soil near the base of the plants. If the soil feels dry to the touch, it's time to water. Avoid watering on a fixed schedule and instead water as needed based on the moisture level of the soil.

Deep Watering: When watering Knock Out Roses, provide deep, thorough watering to encourage deep root growth. Water at the base of the plants rather than overhead to deliver moisture directly to the roots. Ensure that the water penetrates the soil deeply, reaching the entire root zone of the plants.

Mulching: Apply a layer of organic mulch, such as shredded bark or compost, around the base of the Knock Out Roses. Mulch helps retain soil moisture, suppress weeds, and regulate soil temperature, reducing the frequency of watering required. Keep the mulch a few inches away from the stems to prevent rot.

Established Plants: Once Knock Out Roses are established, they generally require less frequent watering. Water the plants deeply but infrequently, allowing the soil to dry out slightly between waterings. This encourages the development of a healthy root system and reduces the risk of root rot.

Watering Schedule: As a general guideline, water Knock Out Roses deeply 1-2 times per week during the growing season, depending on weather conditions and soil moisture levels. Adjust the frequency of watering as needed to ensure that the plants receive adequate moisture without being overwatered.

By following these watering guidelines and adjusting your watering schedule based on the specific needs of your Knock Out Roses, you can help ensure that they remain healthy, hydrated, and thriving in your garden landscape.

If your Knock Out Roses are not blooming, several factors could be contributing to the issue. Here are some common reasons why Knock Out Roses may fail to bloom:

Insufficient Sunlight: Knock Out Roses require full sunlight to bloom profusely. If they are planted in a location that receives partial shade or less than 6 hours of direct sunlight per day, they may not bloom as well. Ensure that the roses are planted in a sunny spot to encourage flowering.

Pruning: Improper pruning practices can affect the blooming of Knock Out Roses. Pruning at the wrong time or too heavily can remove flower buds and reduce blooming. Avoid pruning the roses during the spring and summer months when they are actively growing and flowering. Instead, prune in late winter or early spring before new growth begins.

Overfertilization: Excessive fertilization, particularly with high-nitrogen fertilizers, can result in lush foliage growth at the expense of blooming. Avoid overfertilizing Knock Out Roses and follow the recommended dosage instructions on the fertilizer package. Use a balanced fertilizer formulated for roses and apply it according to the recommended schedule.

Watering Issues: Inconsistent watering practices, such as underwatering or overwatering, can stress Knock Out Roses and inhibit blooming. Ensure that the roses receive regular watering, especially during hot and dry periods. Water deeply at the base of the plants to encourage deep root growth and avoid overhead watering, which can promote foliar diseases.

Disease or Pest Infestation: Pest infestations or diseases can weaken Knock Out Roses and affect their ability to bloom. Common pests that may attack roses include aphids, spider mites, and rose slugs, while diseases such as powdery mildew and black spot can also impact flowering. Monitor the plants regularly for signs of pests or diseases and treat them promptly with appropriate controls.

Environmental Stress: Environmental factors such as extreme heat, drought, or poor soil conditions can stress Knock Out Roses and affect blooming. Ensure that the roses are planted in well-draining soil and provide supplemental water during dry periods. Mulching around the base of the plants can help retain soil moisture and regulate temperature fluctuations.

Young Plants: Newly planted Knock Out Roses may take some time to establish themselves before they start blooming profusely. Be patient and provide proper care, including adequate sunlight, water, and nutrients, to help the plants establish strong root systems and encourage blooming in subsequent seasons.

By addressing these potential issues and providing optimal growing conditions, you can encourage your Knock Out Roses to bloom vigorously and enhance the beauty of your garden landscape.

Winterizing Knock Out Roses is crucial to protect them from harsh winter conditions and ensure their health and vigor in the following growing season. Here are steps to effectively winterize Knock Out Roses:

Mulching: Apply a layer of organic mulch, such as shredded bark or compost, around the base of the Knock Out Roses. Mulch helps insulate the soil, regulate temperature fluctuations, and retain moisture, which is especially important during winter. Aim for a depth of 2 to 4 inches, but ensure that the mulch does not touch the stems to prevent rot.

Watering: Provide adequate moisture to the Knock Out Roses before the ground freezes. Deeply water the plants to ensure the roots are hydrated and healthy going into winter. However, avoid excessive watering, as soggy soil can promote root rot. Monitor soil moisture levels and water only when necessary.

Pruning: In late fall or early winter, prune the Knock Out Roses to remove any dead, diseased, or damaged branches. Additionally, prune back any long or leggy growth to maintain a compact shape. Aim to create an open canopy that allows for good air circulation, which helps reduce the risk of disease.

Wrapping: Consider wrapping the lower portion of the Knock Out Rose bushes with burlap or protective fabric to shield them from harsh winter winds and temperature fluctuations. This is particularly important for newly planted or young bushes with thin bark, as they are more susceptible to winter damage.

Fertilizing: Avoid fertilizing Knock Out Roses in late fall or winter, as this can stimulate new growth that may be vulnerable to frost damage. Instead, fertilize the plants in early spring, just as new growth begins, using a balanced fertilizer formulated for roses.

Pest and Disease Control: Before winter sets in, inspect the Knock Out Roses for signs of pests or diseases. Treat any issues promptly with appropriate organic or chemical controls to prevent them from worsening during the dormant season.

Snow Management: If heavy snowfall is expected, gently brush snow off the branches of the Knock Out Roses to prevent damage from the weight of the snow. Avoid shaking the branches, as this can cause breakage.

By following these winterization practices, you can help protect your Knock Out Roses from winter damage and ensure their continued health and beauty in the coming seasons.

Our Process

We have perfected packaging and shipping plants & trees! That is why we DO NOT use any third-party fulfillment like most other online retailers. Your trees go straight from our farm to your door, safely packaged by our team of seasoned professionals. Our process ensures your plants leave our facility and arrive to your door in the best condition possible!