Pruning Knockout roses is shear simplicity. Follow my quick trimming instructions and discover how and when to prune easy-does-it Knock Out rose bushes.
Deadheading Knockout Roses
This plant’s flowers are self-cleaning so the shrubs never need dead-heading. That doesn’t mean you can’t or shouldn’t snip off the old, faded blooms if you feel that they mar the beauty of your Knockout rose garden.
Rosa Knockout blooms in flushes. It will bloom for a few weeks, then rest for a few weeks, then bloom again… It will do this all summer long as long as you don’t allow it to set seed.
They will set hips (the seed containing part of a rose) if they are not deadheaded. Once this happens, flower production will cease for the season.
If you have just a couple of bushes, you can deadhead them with a hand held clipper. If you’ve got a 20 foot blushing Knockout rose hedge, trim it back a few inches with a power shear after each flush of bloom.
How to Prune Knockout Roses
Knockout roses growing at Harry P. Leu Gardens in Orlando, Florida.
Knockout roses pruning is simple.
Knock Out rose bushes don’t require the picky hand pruning that many roses need.
They can be sheared like any other hedge, or left unpruned.
Cutting them back to 18 inches each spring will result in more vigorous growth and more abundant bloom. After trimming easy does it Knockout roses back hard in this fashion, the roses will grow 3-4 feet high and wide in one season.
Pruning Double Knockout Roses
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Knockout rose pruning techniques are the same for all varieties of Knockout roses.
When to Trim Knockout Roses
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The best time to prune Knockout roses is in early spring before they break dormancy.
In the coldest part of their hardiness range (zone 5) Knock Out rose bushes may die to the ground but will usually come back from the roots.
The only reason for pruning Knockout roses in fall would be if you want to make them small enough to cover. I don’t think it would be a good idea to prune the bushes in the fall and then leave them unprotected all winter.