The key lime--famously used to flavor the popular dessert, key lime pie--is one of only two varieties of lime sold commercially in the United States. Because the tree can grow well from a seed, you can plant your own potted key lime tree as a patio ornamental. Key lime trees are very cold sensitive, and require intense heat to develop aromatic, flavorful fruit. If you grow a key lime as a patio ornamental, quickly diagnose and fix problems with your tree before they can kill the plant.
Prune away frost damage if your tree shows signs that it was damaged by frost or freezing. The tips of frost damaged branches will swell and appear waterlogged. They will then turn black. Any key lime buds will wither and fall off of the tree. Leaves will turn yellow.
Wait several months to prune a key lime tree so that you can tell the extent of the damage. Then cut back damaged twigs right to the base of the branch. Continue to watch the weather and move your tree indoors whenever temperatures drop below 65 degrees.
Check the soil if the leaves turn yellow and fall off and the twigs seem to die back to the larger stems. This is a sign of root rot, which is caused by poor drainage in the soil. Key lime trees will do well in any well drained soil. If the soil contains too much clay, it may be holding water. In addition to the content of the soil, you may also check to make sure that the drain hole is not blocked. Unblock the drain hole in minor cases, and water less frequently.
For major root rot, dig up the root ball and shake off excess soil. Then trim away any diseased roots with a pair of pruning shears. Select a new container with a proper drain hole and rich, well-drained potting soil. Then re-pot the key lime tree.
Fertilize your tree less often by decreasing the amount of liquid fertilizer that you put in the watering can when you water your tree if the tips of the leaves seem burnt and there is a white salt ring in the soil.
Pour insecticide soap into a garden hose spray applicator and attach it to the end of your garden hose. Spray leaves of a tree with the garden hose if the leaves curl into a cup shape, or have a silvery, scratchy appearance. This is a sign that your key lime tree is infected with aphids or spider mites.
Spray tree with a fungicide if the leaves become covered with a powdery substance; develop a texture like sandpaper or irregular oily spots. These are all signs of fungus and mildew infestation. To do this, pour the fungicide into the holding tank of a spray applicator. Prime the applicator's pressurized valve by grasping the handle and pumping it up and down. Then grasp the wand and open the valve. Pass the wand back and forth over the canopy of the tree.
Spray the tree with horticulture oil if the leaves or bark develop small removable colored spots on the bark. This is a sign of scale insects. To spray the tree with horticulture oil, use a spray applicator following the same process as you used for the fungicide in step 6.