The trees are 6 years old and have never grown 1 lemon. I've yet to see any flowers, and half the time I'm lucky if the trees have branches ( I used to get a little carried away with pruning).
So this year, for the first time, I brought the trees outside and I fertilized them at least every 6 weeks with a citrus fertilizer. I did see a lot of growth and I've had to prune the trees back a little. I really need to get bigger pots for them, but I'm afraid I won't be able to carry them in the house if I do.
Anyway, lately, the leaves look very yellow and are beginning to drop off - even with all my extra care!
I went online to see if I could find a cause and a solution for yellowing leaves, and discovered a forum on gardenweb.com. After reading many comments, I decided to get my hands on some Dyna-Gro Foliage Pro. Many growers of lemon trees swear by this stuff. I bought a small bottle that I found on amazon.com and have saved the customers' reviews page.
Today, I mixed a teaspoon of DGFP with a gallon of water and fed the trees. Then I used the solution half-strength (1/2 tsp. per gallon) to spray on the leaves. I simply filled a spray bottle half-full with the solution, and then filled the rest with plain water. I hope this helps to really green the leaves up. I will post results as I see them.