Why is my guava losing leaves?

Guava naturally sheds some leaves before flowering (February–March) — this is normal and healthy. Abnormal leaf drop is caused by: root rot from waterlogged soil (check pot drainage immediately); sudden temperature drop below 8°C (cover with frost cloth in North India winters); or scale insect infestation (look for small brown bumps on stems). If the tree is otherwise healthy and flowering follows the leaf drop, no action is needed.