A couple of years ago I ordered a lemon tree and a key lime tree. I have yet to bear fruit and every year when I bring these into my house for the winter all the leaves drop off. I water them pretty sparingly and once a month I water them with an epsom salt mix. I'm not sure if my weather conditions are not right here in Ohio, or if there might be more care needed. I just can't seem to get it right. The plants are about 1 1/2 feet tall and I have them in a sandy soil mix in about a 2-3 gallon pot. Can you help?