Lemon trees require very little pruning, so if you are not inclined to trim your lemon tree, you can get away with some basic pruning once every two years or so. However, the trimming and pruning process itself must be done correctly to avoid infection, and more frequent trimming can help the trees get more light and produce more fruit.
Identify the graft joint. This is a swollen area usually located 1 to 2 feet off the ground. Any shoots coming off the tree below this area should be trimmed off right away so they will not diminish fruit production.
Look for branches that cross in the center. Pruning and trimming are mainly intended to allow more light into the tree, resulting in a healthier plant and more fruit production. Crossing branches thin the light.
Thin the interior of the tree. You can start on the ground using the hand shears and the long-handled pruning shears. Walk around as you trim to make sure that you are trimming evenly. Cut thin cross branches first. Always cut on an angle.
Cut off thicker branches if necessary. Ideally you will have three thick branches growing out from the main trunk of the tree with smaller, fruit-bearing branches coming off those main branches. If the tree can support more than three without interfering with the light that the leaves are getting, you can leave more thick branches in place. If you do cut them, use the pruning saw and cut at an angle.
Trim the top. You will need to use the ladder for this part in most cases. Use the pruning shears to sparingly trim the top branches--cut crossed ones first--to let more light into the center of the tree's foliage.