Answer: Unfortunately, based on your description I am not certain what is happening to the buds. It is possible that aphids have attacked the growth tip of the plant and the black you see is actually sooty mold that often accompanies aphid activity along with distorted foliage or buds. Or, it might be a fungal or bacterial infection related in part to the weather conditions this summer. I would suggest you consult with your local professionally trained and certified nurseryman and/or county extension. They should be able to help you diagnose the problem. They may appreciate a freshly cut sample enclosed in a clear plastic bag and kept cool so it stays fresh as well as some photos of the overall plant and closeups of the affected blooms. Once you have a specific diagnosis you can decide how to treat it. If a chemical control is needed, your county extension will have the most up to date information on what to use and how/when to apply it for maximum results. I'm sorry I can't be more exact for you long distance.
Q&A Library Searching Tips