Cause Physiologic: any sudden change in environment or even a gradual change to below-optimum growing conditions. Cold drafts, cold water, dark location, time of year, or simply moving it to a different location in the house can cause leaves to drop. This plant needs plenty of indirect light and 60°F to 70°F temperatures.
Symptoms As days get short in late fall, green leaves often drop, leaving the tree almost bare. Green buds generally remain on branches, although some may dry up. It is natural for some green leaves to drop in spring as a new flush of growth begins.
Cultural control Plants remain alive and generally produce new foliage when the problem is corrected.
- Set near a window with plenty of light but no direct sun.
- Give the plant only room-temperature water. Do not allow it either to dry between waterings or to remain soggy.
- Protect from cold drafts, even when bringing it home from the store.
- For nurseries, the use of ethylene blockers (such as EthylBloc) before shipping may be helpful.
Reference Al-Khalifah, N. S., and Alderson, P. G. 1999. The effect of auxins and ethylene on leaf abscission of Ficus benjamina. In Biology and Biotechnology of the Plant Hormone Ethylene II (pp. 255-260). Springer, Dordrecht.