Answer: It could be pollution, but there are four different fungal diseases that cause black spots on hibiscus leaves. Just in case it is a disease, remove the affected leaves to keep it from spreading. Smaller than normal flowers might indicate overwatering or overfertilization. If buds drop before opening, it's because of overwatering. To encourage blooms, pinch out the tips of growing stems. You can remove old wood this spring to encourage more new stem growth, as well as maintain the plant's vigor.
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