Question
I live in palm springs calif. are weather is cooling off 88o/o to 92o/o. write now....i have 2 mature climbing rose bushes 21/2 years in the ground. they are turning yellow...they are being watered the same as alleways, they are on a wall facing the north.
help.
Charlotte

Answer
If your climbers have done well for 2 1/2 then the yellow leaves are re-acting to something that was different a couple or more weeks ago as that is about how long it takes a rose to show stress. Prolonged heat will cause rose leaves to go yellow. Also a rose needs normally 5 gallons of water once a week but in high heat of course it needs more even on a daily basis. The moisture should reach the roots not just go down for a few inches. Too much water can also choke the roots and make then unable to take any liquid or nutriens up. Anything sprayed or even chemical fertilizers used in high heat can cause leaves to yellow. If your soil has a lot of clay in it roses will go under stress in high heat. Those are the main reasons rose leaves go yellow plus lack of nitrogen which I am sure they are getting.
Because you have said that the roses have done so well for a long period of time, it really does appear that it is just stress the climbers are experiencing. But to make sure check and see just have far down the water has gone. Also wash down the climbers before the day gets really hot as the leaves can take in water as well as the roots. Even placing a mulch all around the base of the climbers is a good idea as roses really enjoy cool roots and so grow better. Hope this helps.