Key limes (Citrus aurantifolia) are shrubby citrus trees that reach 16 feet tall. This thorny tree has oval leaves 1 to 3 inches long. The 1-inch flowers are yellowish white with lavender edges. Blossoms appear abundantly from May to September. The fruit is round and turns yellow when ripe. Commercial key limes are normally picked while still green. Key lime fruit are smaller, seedier, tarter and stronger scented than other limes. This citrus tree is very sensitive to cold temperatures. Key limes need lots of heat and direct sunlight to produce fruit.
Wash a 10- to 15-gallon container with soapy water and rinse with one part bleach mixed with nine parts water. Cover the bottom with a layer of small stones to add weight to the plant pot. Plant the young key lime tree at the same depth that it is growing in the original container. Use a mixture of one part peat moss and three parts potting soil.
Place the plant pot in a deep tray to catch water overflow. Locate the container in an area with good air circulation and full exposure to sunlight. Ideally a key lime tree needs six to 12 hours of sunlight each day. Protect the citrus tree from cold drafts.
Water the key lime tree three times a week for the next three weeks. Reduce the watering to once a week. Do not over-water the tree, but do not allow it to wilt. Pour the water in the top of the plant pot until it drains out the bottom. Remove the excess water after 10 minutes. Mist the key lime tree with lukewarm water each day. Wipe the leaves down with a damp sponge whenever they are dusty.
Prune the key lime tree to shape and maintain the desired size. Remove any random suckers that appear on the tree trunk with a sharp, clean knife.
Feed the key lime tree with 1/2 pound of slow-release 10-10-10 fertilizer. Scratch the dry fertilizer into the soil on the surface of the container. Water immediately after feeding the tree to start the fertilizer working. Feed every six weeks for the first three years.
Pollinate the flowers by rubbing the inside of the blooms with a small paintbrush or cotton swab. This replaces bees as the pollinator and increases the chances of producing limes. Let any developing fruit ripen on the tree.