I have 12 knock out rose bushes. This morning I saw that the older ones (4 months) have a lot of yellow leaves through the middle of the bush. I don't know why or how to treat this problem. Would appreciate an answer.
Knock Out Roses
Here is a link to an article I wrote on this subject, please give it a read: https://www.gardeningknowhow.com/ornamental/flowers/roses/yellow-rose-leaves.htm
Here is another article for you as well: https://www.gardeningknowhow.com/ornamental/flowers/roses/leaves-falling-off-roses.htm
Please let us know if you have any questions.