lotusblos, Citrus tree problems with bark that is cracking and splitting can frequently be more or less common, and may not be cause for alarm. Cracked bark can be caused by the natural growth process, or rapid changes in weather conditions or temperature during various parts of the growing season. However, if your tree is showing other symptoms, such as gumming, discoloration or die back, your tree may be infected with one of several disease. I have several lemon trees that develop vertical bark splits from time to time. The splits are generally anywhere from 3 to 5 inches long, and of very shallow depth. I have several varieties of lemons. The splits to my trees have never caused any actual damage, or hardship to the tree, nor do I ever see any type of bleeding or oozing from them. All of my lemon trees remain very healthy and producing fruit throughout the year. - Millet