|I have a 5 year old Rose of Sharon bush, about 7ft tall, with lavender flowers. It has a SW exposure, and is right next to the corner of the house. It probably receives above-average moisture as it gets a fair amount of runoff from a roof downspout.
In almost all ways it seems healthy and grows like mad. Each year it is absolutely loaded with flower buds. The problem is, 75% or more of the flowers fall off before they fully open. They fall to the ground as cylinders that are mostly formed flowers but look like they are about a day or two from opening.
Any ideas what may be causing this? Too much/little water, some kind of soil deficiency, etc.
|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. Next spring try fertilizing with a low-nitrogen, high phosphorus (bloom enhancing) fertilizer.
Established plants require infrequent, but deep soakings during the growing season. This winter you can prune your plant back, removing all but two buds on each stem. These buds will produce new flowering wood in the spring.
Hope the above measures help your Rose of Sharon shape up and bloom prolifically!