Question
Hi Lynnette! I have climbing roses on a trellis I made from white pvc plumbing pipe. This trellis is under my room overhang and rain does not fall on it. I noticed lately that the trellis is really dirty from black substance that might be "industrial fallout". The leaves are blackened but the plant looks healthy. I have been spraying for leaf fungus. Can the leaves be cleaned by spraying a mild detergent? Any suggestions? Thanks, Bill

Answer
Leaves have to breathe and anything you spray on them impedes their work of making photosynthesis which is a lifeline for the plant. Sprays leave a residue on the leaves and although they may solve the problem of  fungal diseases, they do in a small way damage the leaves. I would be more concerned if the fallout got on your roses at the start of the season. If it is mainly towards the end of summer, then the rose is going to drop it's leaves anyway and that will help keep the rose healthy. I am assuming here that you get a cold enough winter to make the rose drop it's leaves.