|My roses started out very well this season - lush, green leaves. Then some developed black canes and became very stunted, not producing as many flowers, and the ones they did produce were very small. Now they aren't producing flowers at all.
I know I have a layer of clay about 2-3 feet below the topsoil, so I try not to overwater them. I have used fertilizer and sprayed my roses with a mixture of garlic, mineral oil, dish soap and water to try to combat our ever prevalent black spot. This has helped trememdously as my roses don't seem to be as infested with the disease this year.
I haven't been spraying them very often, however, because I was afraid that our intense summer heat in Texas would cause the bushes to burn. Perhaps the oil is part of the problem.
I think when this summer heat is over, I need to ammend the soil with compost, which you have suggested I do this fall by lifting the plants and adding the mixture. Is it safe to do this with older plants as well?
|There are some fungal disease of roses that can attack the canes. I would prune the infected canes out and dip the pruning tool in rubbing alcohol between cuts to avoid spreading a problem. The problem may also be at or below the soil. Carefully scrape back a little bark at the soil line on the plants showing the symptoms and see if it is a healthy cream color underneath or a pecan brown color, indicating dead tissue.
Soil that is too wet or too dry can cause problems for roses.
I would go ahead and transplant this fall. I have moved older roses several times in the south with no problems.
I have not tried the mineral oil spray, but have concerns regarding its safety for the plants. Oil sprays in the summer (temps above 90 degrees) can burn foliage, so this may be contributing to the problem.
Hope this helps. Good luck with your roses!