Question
Hi,

I have two large rose bushes which develop yellow leaves. At the beginning of the season the leaves are very healthy. Can you let me know the reason behind this and the necessary treatment?

I live in Yorkshire, England.

Thanks.

Answer
I would need a bit more information to give you a more accurate answer so all I can do is list the reasons that rose leaves go yellow.
If the roses were just planted then it could be transplanting stress, especially if fertilizer was put in the planting hole. But if they have been in the same position for a whole season, then the following could be the reason. Leaves that go yellow at the base of the plant are due to the roots not being happy. It could be over or under watering. Also a spring that warmed up quicker than usual and this would put the rose under stress such as needing more water than usual. Tiny spider mites cause yellow leaves as well as insects that attack the roots of the rose. A lack of certain nutrients in the soil but usually most soils are okay for growing a rose. A spray used on the leaves which has clogged up the stomata so the leaves can't breathe. The last two suggestions would show up as yellowing leaves from top to bottom on the bush. Where on the rose bush the leaves are turning yellow is also a very good indicator what is cussing the problem. Sorry I could be more specific.