I have a Kombava tree on my balcony that seems to been hit hard by winter this year. It has survived past winters without problems but this year it started losing its leaves in mid Feburary. It was fine through our very cold December and January, but in Feburary we had a stretch of very warm days. Following this warm stretch (when it got cold again), it started to lose a considerable number of leaves. Now, a month later, all the remaining leaves have dried and turned light yellow. Many of the branches are similarly dried and yellow. The main "trunk" (small) still looks alive and green as do a couple of the side branches. Is there any way to save it? Should I try pruning? How? What happened? Thank you.
A kombava tree, in fact all citrus trees, develops more and more hardiness as the temperatures gradually drop lower going into winter. Unfortunately, all or most, of the hardiness that your Kombava tree developed, was quickly lost when the warm weather period interrupted the regular winter cold. During normal winters a kombava tree is able to withstand the cold of your balcony, but due to losing the hardiness it had previously build up, due to the warm temperature, the tree lost all of it defense's against the cold. Nick the trunk, and larger branches to see if the cambium layer is still green. If the cambium remains green the tree has a good chance of surviving. In treating container citrus trees severely injured by cold, two courses are open: (1) leave them alone; (2) cut them back part way. Everything considered, leaving them alone is the best plan. For some time following frost injury it is impossible to determine how much pruning should be undertaken. Nothing can save trees, or parts of trees, that have been frozen. Much labor, and tree parts, can be saved by waiting until the exact extent of the injury can be determined. This cannot be decided until spring growth starts. When new shoots have grown far enough to make it reasonably certain that the branches will not die back further, is soon enough to start any needed pruning. The very best to you and your tree. - Millet (1,401-)