KC Gardens

Dennis Patton: It’s time to think about pruning Knock Out roses, and here’s how

By Dennis Patton

Easy care roses have become a staple in the landscape. Don’t recognize the term easy-care? Maybe you would by the most commonly planted varieties, Knock Out roses. This one group of plants is prized for its season-long flowering and ease of care.

The most popular call to the Johnson County Extension office Gardening Hotline is about Knock Out roses. The questions usually revolve around pruning. People want to know two pieces of information — when to prune and how to properly prune this rock-solid plant.

The ideal time to prune any type of rose is in the very late winter or early spring. They are best pruned as new growth is starting to develop. They can be pruned a little later into spring with good success. Fall is the worst time these plants should be pruned, as fall pruning can lead to winterkill.

How to properly prune Knock Out type roses is more difficult to explain. This plant is so vigorous and will thrive regardless of whether it is an extreme trimming or a light haircut. One of the common complaints about the plant is that it grows bigger than listed on the plant label. The amount of pruning can help control the overall size. Of course the ideal size in your garden depends on its placement. Here are a few different pruning concepts to help ensure you have the best-looking rose.

If you prefer larger plants you’ll do a light trimming. This would include removing the dead wood and branches that are crossing and growing toward the inside of the bush. Good light penetration is important for nice flower development. You could stop at this point and the plant would be fine.

One drawback to this light trimming is, over time, the canes become very thick and woody resulting in fewer flowers at the bottom of the bush with a leggy appearance. The next step in pruning would be removing the oldest, thick, woody canes to the ground in the spring. This usually involves a saw to cut them off at ground level. This allows for new canes to sprout and keep the plant’s canes younger and more vigorous. The greatest number of flowers comes from younger less-woody stems.

Neither one of these methods will help control size. A more extreme method of pruning will be required. The first step is always the same; remove the dead, dying, crossing and inward-growing branches. The next step is the same as above; cut out the old woody canes to the ground. After these cuts are made the size of the plant can then be controlled.

The last step is to cut all remaining canes back to somewhere between one to two feet. Trace down each remaining branch and look for a nice plump bud pointing outward on the plant. Make the cut at this point. Thin out the small wispy canes leaving between three and five canes about the size of your thumb’s diameter. When you have completed the process the bush will look like a bunch of sticks, but they will quickly recover. Even with this harsh pruning a healthy plant will still reach three feet or more by fall.

One last tip, if your plant is outgrowing its allotted space don’t fertilize. Additional fertilization just makes the plant grow bigger. If you feel the need to feed make one application at pruning. The good news is these plants are so forgiving you really cannot mess it up. Easy care rose pruning will result in a healthier and better-looking plant with more flowers. I would call that a win-win!

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