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White Knock Out® Rose Tree

Rosa 'Radwhite' (PP #20,273)

White Knock Out® Rose Tree

Rosa 'Radwhite' (PP #20,273)

This product is currently out of stock and unavailable.

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How are the heights measured?

All tree, and nothin' but the tree! We measure from the top of the soil to the top of the tree; the height of the container or the root system is never included in our measurements.

What is a gallon container?

Nursery containers come in a variety of different sizes, and old-school nursery slang has stuck. While the industry-standard terminology is to call the sizes "Gallon Containers", that doesn't exactly translate to the traditional liquid "gallon" size we think of. You'll find we carry young 1-gallons, up to more mature 7-gallons ranging anywhere from 6 inches to 6ft.

How does the delivery process work?

All of our orders ship via FedEx Ground! Once your order is placed online, our magic elves get right to work picking, staging, boxing and shipping your trees. Orders typically ship out within 2 business days. You will receive email notifications along the way on the progress of your order, as well as tracking information to track your plants all the way to their new home!

Why are some states excluded from shipping?

The short & sweet answer is: "United States Department of Agriculture Restrictions." Every state has their own unique USDA restrictions on which plants they allow to come into their state. While we wish we could serve everyone, it's for the safety of native species and helps prevent the spread of invasive disease & pests. We've gotta protect good ole' Mother Nature, after all.

About Me

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The White Knock Out® Rose Tree is a bush of pure beauty. The rounded, leafy crown is supported by a strong trunk, and the pure-white blooms are carried continuously from late spring into the fall, and we do mean continuously. Making a plant about 5 feet tall, it is the perfect colorful accent in your garden beds, or a spectacular feature in a planter box. The clusters of large white flowers stand out against the very dark-green leaves, and brighten your garden in a most remarkable way.

  • Clusters of large white blooms open from pink buds
  • Flowers from late spring continuously into fall
  • The very dark-green leaves make a wonderful background
  • Disease-resistant, so the leaves are always fresh
  • Excellent for planter boxes in warmer zones

Plant your White Knock Out® Rose Tree in full sun for the best results. It will tolerate a couple of hours of shade each day, but not more. Plant in rich, well-drained soil, including clay soils. In pots mix garden soil with regular potting soil for the best results. Water regularly, and feed in spring. Use liquid rose-food through the season for plants in pots. Remove spent flower clusters and prune in spring for the best results. Resistant to blackspot and rust diseases.

Plant Hardiness Zones 6-11
Mature Width 4
Mature Height 6
Zones 6-11

The stunning White Knock Out® Rose is simply the best white landscape rose around. Perfect in every garden setting, bringing beauty and brightness, and blooming continuously from late spring into fall. It is regarded as the rose with the longest bloom period, so you can’t beat it for months of garden beauty. Typically growing to only 3½ feet tall, it is perfect in beds, but sometimes you need something taller – but why pass up such beauty for something not quite as good? We decided not to, so we asked our skilled growers to take buds of this fabulous rose and attached them to a short trunk of another rose, making wonderful taller plants like miniature trees. That’s how the wonderful White Knock Out® Rose Tree came about, and they are just fabulous. About 5 feet tall, these are stunning, stand-out features for your beds or for growing in boxes – amazing crowns of glowing white blooms set against very dark-green foliage, all standing on a sturdy trunk. You will love it.

Growing the White Knock Out® Rose Trees

Size and Appearance

The White Knock Out® Rose Tree is a deciduous shrub made up of a single upright stem about 2 feet tall, supporting a rounded bush of branches that is between 3 and 4 feet tall. Overall, the plant is about 5 feet tall, give or take, depending on how you prune. The crown is dense and bushy, with beautiful foliage that – thanks to the disease-resistance of this plant – is always healthy and fresh. The leaves are exceptionally dark green, with new leaves almost black. They are divided into smaller leaflets, up to 7 in one leaf, with each leaflet about 1½ inches long, oval, with serrated edges. Almost as soon as the new leaves have grown out in spring you will see the clusters of buds developing, and before you know it your bush will be in bloom. The flowers are in clusters of about 5, and each bloom is large, almost 3 inches across. They are pink in the bud, opening to reveal a bowl of about 10 petals surrounding a central yellow cluster of stamens. The petals are pale yellow when just open, quickly turning to a pure, snowy white. Young flowers have a soft floral fragrance. This bush is always covered in blooms, from late spring into fall, continuing even through the heat of summer.

Using the White Knock Out® Rose Tree in Your Garden

The White Knock Out® Rose Tree is a wonderful way to bring instant-height into your beds, standing above smaller shrubs and flowers, yet leaving room for them to grow happily. By adding an extra layer of leaves and flowers you enrich the look of your garden in a way you won’t believe could be this good. Grow it at the center of a formal bed, or in a bed running alongside a path or driveway. Use it at corners, or where a path changes direction. It instantly brings a touch of grace and form to any garden space. It is also wonderful growing in containers and planters, looking spectacular in the corner of a terrace or porch, or standing beside a door. Plant trailing plants beneath it for added richness.

Hardiness

The White Knock Out® Rose Tree is not as hardy as the basic bush is, because the branches are up in the air, with less protection from snow and the warmth of the garden. It will be perfectly happy in a bed or box in zone 7, and could be grown in zone 6 and even zone 5 if you bury it in the ground for the winter. It is fabulous in warmer zones, and grows perfectly even in zones 10 and 11, with the mildest of winters.

Sun Exposure and Soil Conditions

Plant your White Knock Out® Rose Tree in full sun. It will take a couple of hours of shade a day, but more will reduce flowering noticeably. In the garden grow it in rich, moist but well-drained soil enriched with organic material like garden compost, and mulch over the roots with more. Keep moist, and avoid long periods of dryness, which can inhibit flowering. (For more drought resistance grow this rose as the regular bush). In planters, use a mixture of 25% garden soil and 75% outdoor potting soil for the best results.

Maintenance and Pruning

Although some minor pests like greenflies are possible, our organic Neem Oil Spray will easily control them, and you won’t need to use any nasty chemicals to succeed. This bush is very resistant to blackspot and rust, so the leaves stay green and healthy, without dropping off. Fertilize in spring, and feed bushes in pots regularly through the season with liquid rose food.

Remove flower clusters as the last bloom fades, as this stimulates the production of more side-shoots, and more flowers. Remove any stems that sprout from the ground or lower down on the trunk – these are a different rose that won’t bloom. In early spring prune out any weak or damaged stems from the crown, and shorten back the stronger branches to between 12 and 18 inches long. This will keep the crown of your rose tree compact and vigorous. Be careful to never cut off the crown, as the remaining stem will not produce the correct rose.

History and Origin of the White Knock Out® Rose Tree

The White Knock Out® Rose was created by Will Radler, the creator of the original red Knock Out® rose, and the breeder of many more. To make this one he used pollen from one of his earlier roses, Alaska or Pink Beauty (‘Radsweet’), on an unreleased seedling called ‘Radmom’. That plant was a seedling of an older landscape rose called Carefree Beauty® (‘Bucbi’). Among the seedlings he grew was one that really stood out for its beautiful white flowers, dark foliage and vigorous, continuous blooming. He named it ‘Radwhite’ and patented it in 2009. It is made available as White in the Knock Out® range of roses. To create the tree-form, skilled propagators implanted buds of this rose at the top of special stems and roots from another special rose, grown only for its vigorous roots and strong, straight stems. Those buds grow out to form the crown of the complete rose tree.

Buying the White Knock Out® Rose Tree at the Tree Center

The very special White Knock Out® Rose Tree is a real beauty, and something you will be proud to grow in your garden. You will be amazed by it, and the impact it has. These rose trees are difficult to make, and always in short supply. Everyone wants one, so be sure to order right now – they will be gone very, very soon.

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White Knock Out® Rose Tree

Rosa 'Radwhite' (PP #20,273)