Q.hibiscus
The leaves go yellow and unopen buds keep dropping off.
Bud drop on hibiscus is commonly caused by nutritional deficiencies, environmental conditions (such as insufficient water, excessive change in temperature), or pests such as thrips or gall midge, which will require a close examination of your plant.
For more information on all of the above, please visit the following link:
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-flowers-hibiscus-blossoms-falling-off-plant.htm
Hibiscus flowers require lots of light, high humidity, and moist soil. They also need regular feeding with fertilizer as directed.
For more information on the care of hibiscus, please visit the following link:
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/how-to-care-for-hibiscus-plants.htm
