Early Hibernation

• Hibiscus plants sometimes will enter into an early dormancy or "rest period" several months before normal dormancy. Hibiscus plants can enter early dormancy for many reasons, but early dormancy is not necessarily an indication of a serious problem. Allow the plant to defoliate (water less frequently if necessary for the leaves to drop) and see if normal growth returns next season. Fertilization or moving the hibiscus where it gets more sunlight exposure may be necessary for the plant to return to normal growth.
  
  

Leaf Spot

• Leaf spot is a potentially serious plant disease; a leaf spot infection that is allowed to reach advanced stages could potentially cause leaves to fall off the plant. The earliest symptoms of this disease are the leaf spots themselves; they are intermittent across leaves and of varying colors depending on the bacterial or fungal disease agent responsible. Seriously infected leaves will defoliate altogether. Leaf spot almost never causes plant death, so to control the disease, simply discard and remove all diseased leaves that fall off the plant and allow the hibiscus to return to normal growth.
  
  

Frost Damage

• If your hibiscus plant was subjected to cold temperatures, particularly below freezing temperatures, defoliation is a natural reaction to damage inflicted by the cold temperatures. Sometimes cold treatments are recommended for insects that are difficult to control through other means. Gardeners can sometimes be surprised to find their hibiscus defoliating after the infestation has been successfully removed. Defoliation is normal in this case, and the gardener need not do anything more than allow the hibiscus to grow back normally.
  
  

Other Possible Diagnoses

• Leaf yellowing and defoliation are among the most common symptoms observed on plants. While early hibernation, leaf spot and frost damage are the most likely reasons for a hibiscus plant to lose its leaves, there are other reasons for defoliation, including insect feeding damage, drought stress or more serious bacterial and fungal diseases that may require the use of a chemical fungicide. If none of the above recommendations restore your hibiscus to full health, you may need to have a university extension office diagnose a sample of the hibiscus plant for you.