The dwarf Mexican lime tree, also called the key lime, is a citrus species native to subtropical regions. This species of lime produces glossy textured foliage with small, bright-green fruit. Mexican lime trees are good to plant outdoors in USDA growing zones 9 through 11, where there is little risk of freezing weather. While the tree is a dwarf variety, the Mexican lime will reach a height of 12 feet in some areas.
Choose an outdoor planting area for the Mexican lime that has a well-draining and nutrient-rich soil in full sunlight. The south side of a building works well, as it provides wind and cold protection.
Test the soil pH of the planting area to verify it is neutral to slightly acidic, with a pH of 6.0 to 8.0 for proper growth. Work ground rock sulfur into the soil with a tiller to lower the pH number, or limestone to raise the pH number. Monitor the soil pH each year and amend as needed using the package application instructions based on the type of soil.
Dig a planting hole that is two to three times as wide as (and the same depth as) the container it came in. Work organic compost into the soil removed from the hole at a rate of 1:1. Set the Mexican lime tree into the hole so the root ball is at ground level; pack the soil around the roots.
Apply 1 inch of water to the soil around the Mexican lime immediately after planting to compact the soil and hydrate the roots. Water the tree two to three times a week for the first months after planting to assist with root establishment. Provide supplemental water to an established Mexican lime tree when the weekly rainfall amount is less than 1 inch.
Fertilize Mexican lime trees with a high-nitrogen tree fertilizer once a month during the growing season of April through October. Follow the package application instructions based on the size of the tree.
Place a 3-inch layer of organic mulch under the branch drip line of the Mexican lime tree, starting 6 inches from the trunk to prevent moisture build up. Refresh the mulch each year to maintain an adequate level.
Prune the tree in spring to control the size of the canopy and remove dead or diseased branches. Regular pruning maintenance is not required for Mexican lime trees.