Knockout Vs. Heirloom Roses: How To Prune Each Type For More Beautiful Blooms

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Knockout Vs. Heirloom Roses: How To Prune Each Type For More Beautiful Blooms

Knockout roses are relatively new to the plant scene, having been around for just over 20 years. These roses were hybridized by William J. Radler, providing homeowners with a low-maintenance way to grow beautiful blooms without the need for excessive use of chemicals. On the other hand, heirloom or heritage roses, which have been around for centuries, are more prone to disease and require more effort than knockouts. These roses have been developed from wild roses and have become a popular addition to landscaping. If you are a lover of all kinds of roses, you may have both knockout and heirloom varieties in your garden. To ensure the prolific growth of each type, it is essential to know what kind you have and how to prune it correctly.

lthough heirloom roses come with their own challenges, they have a unique scent and produce gorgeous blooms that knockouts cannot match. These roses have not been bred to resist disease and are more prone to fungal issues. Nevertheless, keeping them healthy will reward you with beautiful blooms and a scent that knockouts cannot provide. Conversely, knockouts may not be as showy or heavily scented as heirloom roses, but they are perfect for those who want the beauty of a rose without a lot of work.

Pruning Knockout roses

pruned knockout roses

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Knockout roses are hard to kill, so when you are preparing to prune yours, there’s no need to worry about doing it wrong. The only consequence of bad pruning is that you can end up with an odd shape until it’s time to prune again. Knockout roses should be pruned in late winter before they start showing signs of new growth. In most of the US, this time frame falls around Valentine’s Day. If it’s hard to remember when to prune, just keep in mind that roses are inextricably connected to this holiday.

Garden work doesn’t get much easier than pruning knockout roses. Wear protective rose gardening gloves to spare yourself many scratches from thorns, and use loppers to cut all the canes down to 1 foot tall. This may seem drastic, but these roses grow about 3 feet every season, so this extensive yearly pruning will help keep the bush a manageable size while it provides you with blooms all season. After trimming your knockout roses, look for any damaged canes near the ground and remove those with pruning shears. Once you discard the cuttings, the whole process has been completed in just a few minutes.

Pruning Heirloom roses

man pruning heirloom roses

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While most people prune heirloom roses in February, they can also be pruned in the fall after they have finished blooming. This is the best option if your roses are exposed to harsh winter winds, which can whip around and damage longer canes. For this type of pruning, cut each cane back to about 3 feet tall.

Spring pruning is more about shaping the bush to a desired size while removing damaged and old canes. Do not prune heirloom roses like you would knockouts because they don’t grow as quickly, resulting in far fewer blooms. Trim the canes so they are about 3 to 4 feet tall. Once the plant is 4 years old, remove the oldest canes from the ground so you have no more than six. This relatively new growth will provide the best floral display. Remove all dead and damaged growth.

This is when it is really important to know what kind of heirloom rose you have. Some of these older cultivars only bloom on old wood. If your roses only produce flowers once a year, they are considered “once blooming roses” and should be pruned immediately after they have finished their display, usually in mid to late summer.

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Dr Heidi Parkes

By Dr Heidi Parkes

Senior Information Extension Officer QLD Dept of Agriculture & Fisheries.