A Key lime tree is also called a Mexican lime tree and the West Indian lime, according to the Texas Cooperative Extension website. Native to Asia, it grows well in the southern regions of the United States such as Florida and Southern California. The fruit of the tree is typically no larger than 2 inches across. Resembling a small bush, as opposed to other lime varieties, the Key lime tree needs pruning to control the shape.
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Wait until late summer, just before the tree drops its fruit and develops new buds for the following year. Pull off all of the remaining Key lime fruit from the tree.
Look at the lower trunk of the Key lime tree and locate any small twigs or branches growing out of the soil or horizontally from the trunk. These are called suckers and should be pruned off with hand pruners, flush with the trunk of the tree.
Look for limbs that are brown, gray or black which indicate those limbs are dead. The branches may also be visibly broken. Cut these limbs off of the Key lime tree using a pruning saw and cutting as close to the trunk as possible.
Examine the tree for limbs with visible signs of disease—such as lack of leaves, a spotted appearance or visible mold growth. As with the dead limbs, cut these limbs off as close to the trunk as possible too.
Locate any stem that is smaller in diameter than the thickness of a pencil and prune the stem off near the trunk using the hand pruners. These stems are too weak to support any limes that develop and will eventually break.
Look into the center branches of the Key lime tree for branches that rub against another branch. Prune off the branch near the trunk using the pruning saw to prevent the branches from creating wounds which cause disease.
Shape the remaining limbs of the Key lime tree by cutting the last 3 to 6 inches from the tips of all branches using pruning shears.
Do not prune young Key lime trees until they reach at least 3 or 4 feet tall.