Don't trim them while they are blooming. Even if they stay green in winter, that's still the best time to prune. Once the weather turns really hot, they may pause in blooming and you could do a little pruning then. But the best time is when the plant is dormant. Cheryl

Hi Faye,
I am a novice when it comes to roses, but I bought 6 knockouts, four years ago and have cut them back at various times for various reasons and they recovered.

Even though you will lose quite a bit of the current blooms by pruning now, my experience is that they will soon bloom again (or at least they do in zone5).

Also, since you didn't do any pruning in the spring, you may have quite a few of the little skinny "twigs" that could (and probably should) be cut down to the ground.

Roses of all kinds are often pruned in the summer to control their growth, so you could do it then too, as Cheryl suggested.

(Make sure they have enough room or you will be continually trying to prune them back. Most of the knockouts grow at least three feet wide)

Good luck!
Patti

Thanks to both Patti and Cheryl. I am going to lightly trim them now and then again in the summer. I know now not to put this off.

faye

Knockouts will probably bloom again 2 weeks after pruning, so go ahead and trim them up if you want.

I'm pretty new with these as well. Mine have gotten very, very thick - so much so that I'm a little worried about air circulation. Back when I grew hybrid teas I concentrated on that because it seemed to help with rust (black spot back East). I'm thinking about doing some judicious thinning but don't really know if it is a good idea.

When I'm reluctant to prune any other way, I force myself to "prune" by taking bouquets.

One thing I've noticed about KO is that when a cane is cut back, say by a third, the new growth will be at a sharp right angle. In other words, I'll end up with a straight up cane with what looks like it took a sharp right turn in growth, kind of awkward looking.
Nell

That was going to be my suggestion, to just cut bouquets of roses or just the rosebuds. It is ok to prune KO roses really anytime. They are not meant to be pruned hard back like a hybrid tea in winter, but just to keep their shape and size. KO bloom pretty much all year, esp in the Deep South. Right now, mine in north MS are FULL OF BUDS and beginning to open. BEAUTIFUL! It is also fine to make thinning cuts which is to remove the entire cane to open up and aerate a rose. I usually remove canes that are going in a crazy direction or if things look too crowded. KO roses are pretty easy, thankfully.