The key lime tree, also known as the Mexican lime, is a citrus tree native to the subtropical Indo-Malayan region and produces glossy foliage with bright green fruit. The key lime is a hardy variety that will grow in southern Texas as long as it has winter protection from freezing weather. Do not plant the key lime near overhead wires or close to buildings and paved roads since it reaches a height of 12 feet.
Select a planting location for the lime that has a nutrient-rich and well-draining soil. The tree requires at least six hours direct sunlight from the south side of the home. This location will also give protection from the cold during the Texas winter months.
Test the soil pH prior to planting the key lime tree, as it grows best in a pH of 6.0 to 8.0. Work ground rock sulfur into the soil to lower the pH; add limestone to raise the pH.
Dig a hole for the key lime tree that is the same depth and twice the width as the container it came in. Add organic compost into the removed soil to increase water drainage, as many areas of Texas have clay soil. Set the tree in the hole and gently pack the amended soil around the root ball.
Water the key lime tree every other day for two weeks after planting. Continue to provide supplemental water during the first growing season when the soil becomes dry to 1 inch. Water established trees when the weekly rainfall is less than 1 inch during the growing season.
Fertilize key lime trees each month from April through October with a high-nitrogen fertilizer. Texas soils are generally low in nitrogen and require supplementation for proper growth.
Apply a 3- to 4-inch layer of organic mulch over the soil area under the canopy of the lime tree. Leave a 6-inch gap between the trunk of the tree and start of the mulch.
Pile soil around the lime tree trunk to a height just below the first set of branches in late November to provide freeze protection for Texas winters. Carefully remove the soil protection in early spring. The trunk bark will be tender and damage easily.