Pruning Knockout Roses - Plant for Success

Pruning Knockout Roses is important for maintaining shape, size, and plant health.

Knockout Roses have become widely popular, and it’s no surprise. They provide a lot of the same beauty that ‘old roses’ or ‘tea roses’ have but also provide many more benefits. They are easy to grow, resistant against disease, adaptable to a variety of growing climates, and require little care.

Knockout roses bloom on new wood, meaning flower buds form on the current seasons growth. This is a huge advantage since flower buds don’t have to survive the winter in order to bloom. Thanks to Knockout Roses, homeowners who don’t necessarily posses a green thumb can still appreciate beautiful roses in their landscape.

While little care is needed for knockout roses, they are prone to growing a little out of balance and misshapen if left unpruned. They can also become too large and take over planting beds if not maintained at your desired size. Follow the pruning tips below to get the most out of your Knockout Roses.

How to Prune Knockout Roses

1. Timing

The best time to prune Knockout Roses is in late winter or early spring, right when you see new growth starting to form from the canes of the bush.

2. Get Tools

You’ll first want to make sure you have a good pair of leather gloves to protect yourself from getting stuck by the prickers. Next, you’ll want a good pair of bypass pruners. If you have a more mature shrub and will be cutting into thicker canes than you’ll also want to make sure you have loppers.

3. Determine How Far Back You Want To Prune

There’s no real right or wrong answer when it comes to how far back you should cut your Knockout Roses. It’s a matter of preference, and also it depends on the current conditions of the bush. I usually like to have it so my Knockout Roses grow to be 2-3′ during the season. Since Knockout Roses can grow 2-3 times their size in one season I usually like to prune them back to about 12” in spring.

When deciding where to make cuts, consider the overall shape of the bush. I usually make sure I’m pruning at least far back enough so that the bush can start the season out nice and balanced. Take a look at the pic below, you can see that this bush definitely needs some pruning. It’s misshapen, has dead black and brown branches from where frost got in, and also has weak and crossing branches, especially towards the base.

Notice how far into the shrub the frost damage is. The entire brown area above where the arrow is pointed needs to be cut back. Since this is a main cane I know that I’m going to have to cut the other main canes down to this height to keep the shrub balanced.

When making your cuts, try and cut right above the buds as shown below.

If you want taller shrubs then you don’t have to prune back as far unless you are forced to due to frost damage. Again, it’s really a matter of preference and recognizing where you need to prune to to get to a point where you can create a nice even overall shape.

4. Cut Out Dead Branches

After making your initial cuts to size and shape the plant, chances are you won’t be left with many black or brown dead sections but if there are any left make sure you cut them out. If you’re in a colder climate you’re more likely to see some dead black and brown sections where frost entered the shrub.

5. Get Rid of Weak and Crossing Branches

You want air flow and you want to conserve energy. Weak branches and crossing branches just take energy from the plant. Cut them out.

6. Dead Head and Corrective Pruning As Needed.

A light deadheading as blooms fade during the summer or a month before hosting an event will kick the bloom cycle into gear. You don’t need to deadhead Knockout Roses but it certainly does help encourage more blooms and keep the shrub tidy.

Also, as the season progresses you may need to do some corrective pruning. Sometimes a cane will just wildly take off and stretch out past the main shape of the rose bush. Simply cut these back to where the main shape of the bush is to keep everything uniform.