1. Overwatering: Although the growth of lemons needs enough water, if there is water in the soil, plants will rot their roots and make their leaves fall off. In severe cases, plants will die, so it is necessary to drain the excess water in the soil in time.
2. Over-concentrated fertilization: Too-concentrated fertilizer may burn the roots of lemon trees, leading to the decline of their ability to absorb water and nutrients, which in turn leads to the fall of leaves. At this time, you can wipe off the flower buds, then cut off the rotten roots and replant them. Attention should be paid to controlling watering amount and fertilization concentration after rehabilitation.
The above information is for reference only, and it is recommended to consult a gardener or professional agricultural technician.