If the flower buds on your rose of Sharon are not opening, don't panic. This is a common problem, and there is likely a simple explanation for it—even though it may be too late for you to correct the problem for this year's blooming season.
When Rose of Sharon Should Bloom
Rose of Sharon (Hibiscus syriacus) is also known by the alternate common name of shrub althea. The blooms of this flowering shrub are most welcome, and even highly anticipated, coming as they do in the latter half of the summer—when most flowering shrubs have finished flowering.
This makes it especially disappointing when they don't come at all, or when the plants have numerous buds but the buds never open. In most regions where rose of Sharon thrives, the flowers are best in July and August.
Why Your Rose of Sharon Is Not Blooming
There are many possible answers as to why your rose of Sharon flower buds are not opening, but the most common causes are related to shade, rot or overwatering, and drought:
- Excessive shade: Rose of Sharon will not bloom up to its full capabilities if given too much shade.
- Rot: During rainy summers, rot can set in and ruin the flower buds, although this may not be noticeable from the outside. The same effect can be produced by excessive watering if you water overhead.
- Drought: During dry summers, rose of Sharon flower buds can be damaged from drought and fail to open.
How You Can Solve These Problems
The problem of excessive shade is relatively easy to solve, especially if you are able to exercise some forethought.
This is a plant for full sun. When you are planting the shrub, make sure that you choose a location that receives at least six hours of direct sunlight per day. If you have planted it in an area that is too shady, consider transplanting the shrub to a more suitable location.
When watering your rose of Sharon, always direct the water toward the soil around the plant rather than onto the plant itself.
If you spray high, you will drench the flower buds, which invites rot. Of course, rain will soak the flower beds, and you have no control over that. But if your shrub is properly located—in full sun—the sunlight will help dry the water off the buds after a rainfall.
The problem of drought is the most straightforward issue to correct. Simply keep your plant adequately watered during the summertime, and make an extra effort during periods of drought. How much water should you give your rose of Sharon? The exact amount (and the precise frequency of watering) depends on the conditions. For this reason, rather than trying to put a number on it, just remember this: the soil around your plant should be kept evenly moist. Gently dig down 6 inches into the soil and feel it with your hand. The soil should feel neither dry nor soaked, but rather slightly moist.