Question of the Week – Number 2: June 27, 2019
“Why do my tropical hibiscus and roses-of-Sharon drop so many buds?”
There are two closely related answers to this question. Both involve shortages of water.
Unless you’re in Deep South Texas, tropical hibiscus plants are commonly grown in pots. They’re large shrubs as they mature, and we gardeners too often try to grow them in containers that are really too small.
Potted hibiscus often become root bound and their soil reservoirs are inadequate, as the weather turns hot. We can’t water them often enough, nor can we water them deeply enough. They dry out and the plants wilt, and their reaction is to abort flower buds.
Roses-of-Sharon, or althaeas, are shrubby, winter-hardy cousins to tropical hibiscus. As such, their family traits run deep. They start to bloom in late spring, usually reaching peak bloom about the time summer temperatures kick in at their hottest.
So, even though there may have been rains in the area very recently, the plants just can’t pull the water up to the tops of the growing shoots rapidly enough to meet all the plants’ needs. The plants wilt, and they start dropping buds.
Mulching their root zones will help, and certainly keeping them moist at all times will be a huge help. But bud drop will be a normal occurrence in Texas, especially in years when it turns really hot really early.