Answer: Shrub Althaea (Rose of Sharon) is subject to a disease called bud blight, caused by Botrytis. It's possible that your plant has this problem but it's impossible to tell without seeing it. You might want to take a sample of the problem to your local Extension office for positive ID and registered controls in your gardening region. A second possibility is a little bud worm that feeds on the petals within the unopened flower bud which makes it turn yellow and die before opening. Look for a tiny exit hole on the sepals of the affected flower buds, or open one of the flower buds up and look for damaged petals. There's really no control for bud worms because they are well protected within the unopened flower bud. Good luck with your plant.
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