Q. Why is my lemon tree losing its leaves, yet small fruit are still attached?
Debra Korman, San Jose
A. There are a few reasons that lemon trees drop their leaves. Although we grow citrus in the Bay Area, we don’t have the best climate for it, and cold temperatures can cause what is known as winter leaf drop.
We’ve had some pretty chilly nights lately, so it might be your tree is responding to the colder temperatures. Experts recommend protecting the tree if you know the overnight temperatures are expected to drop into the freezing range — 32 degrees and lower.
Another common reason for leaf drop is overwatering. Check to see if your tree is sitting in wet soil or has an accumulation of water around the base. Too much water can cause root rot, which then leads to leaf drop. Check your irrigation system. Lemon trees are evergreen, but they need a little less water in the winter than they do in the summer.
A lack of nutrients can also cause leaf drop. The recommended application of a citrus fertilizer is once in January or February, again in April or May, and then in August or September.