Answer: Premature flower drop can be caused by overwatering. Some plants (like camellias) just naturally develop more buds than they can possibly support and the plant drops them before they open. But a Rose of Sharon should be able to support all the buds it develops. Overfertilization might also be a factor; too much nitrogen results in luxuriant growth at the expense of flowers. This spring try fertilizing with a low-nitrogen, high phosphorus (bloom enhancing) fertilizer. Established plants require infrequent, but deep soakings during the growing season. Or, your plant may be hosting a population of bud worms or gall midges. Bud worms are easy to spot, just look around, lift up some leaves. If you see the worms or little black droppings, you can spray organic insecticide B.t. (Bacillus thuriengiensis) which will kill the Budworms. Or, the bud drop could be caused by gall midge. Place some buds in a sealable plastic bag. After a day or two, you may see the very small yellowish worm-like larva on the plastic. Control the midge affecting buds with Orthene sprays as needed. I think we've covered all the bases. I hope this information helps.
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