Question
My rose tree leaves are turning yellow and falling off. The trees are well watered and it is winter therefore not hot in Cape Town. Could this be caused by fertilisers? I used "Bounceback and superphosphates" as directed on the bag.

Answer
Roses in warm areas will grow all through the year but during that year will still need a rest. Such as a couple of months to recuperate and then start into flower again. Steadily making a shrub continue to produce flowers is really going against the nature of the shrub. What has happened is that the rose has gone under stress because it is being pushed too fast with the fertilizers. Roses in your area only need very small amounts of any fertilizer monthly. Also if the rose is growing in the sun this can also put it under stress. Three hours of sun in my pacific west coast of North America will be the same as one hour in yours as your sun is much more intense. Although books say roses need full sun, that has now been proven a myth. In your area 5 hours of full sun and the rose will do well. They appreciate shade in the hottest part of the day. I agree with you that it is the fertilizers so if you could give the rose a rest by not applying any nutrients and only watering, I think you will see the leaves not dropping. You didn't say if the rose was n a container. If it is, then the roots are also being burned by the fertilizer.