Answer: Two things come to mind. If your plants look otherwise healthy, this condition is most likely a physiological problem that occurs following alternating dry and wet weather, mild temperatures and cold spells. Poor nutrition can also contribute to this "balling". Give your rose some extra care by mulching the soil well to reduce soil temperature fluctuations and feeding with a high potash complete fertilizer, or phosphate rock and greensand.
If the flower buds form but then turn brown, your plant has the symptoms of a fungal disease called Botrytis. (Botrytis cinerea) This disease prevents the blooms from opening; buds turn brown and decay. Sometimes partially opened flowers are attacked and individual petals turn brown and shrivel. The fungus is always present in rainy seasons when the old blooms are not removed. Be sure to prune away any infected buds to halt the spread. It will also help to remove spent flowers on a regular basis. Fungicides will help control Botrytis. Apply according to label directions - weekly applications may be required during wet springs.
I hope these suggestions are helpful.
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