The Mexican lime tree is a small, bushy tree that is more commonly known in the United States as the key lime tree. The fruit is small, thin-skinned and yellow/green when ripe. There are a few varieties of Mexican lime; most have thorns and are sweeter and more acidic than the common Persian limes found in most grocery stores. The tree is hardy only where the temperature stays above 40 degrees, but it makes for an excellent container tree. Dwarf varieties are available for those with limited space.
Dig a hole three times the diameter of the container you purchased the tree in and the same depth. Clean all lawn turf, weeds and stones out of the dug-out soil. Amend the soil with 1 part compost to 3 parts original soil, if the soil is very heavy. If the soil is of good quality, no amendments are necessary.
Remove the tree from the container carefully, and rinse off most of the medium around the root ball. Do this with a gentle stream of water from a garden hose, so as not to damage the roots.
Create a small mound of soil in the bottom of the planting hole, and place the tree on the mound, draping the roots around it. The level of the tree should be slightly higher than it was in the container.
Fill in halfway up the root ball with soil. Water well to settle the soil around the roots and ensure that there are no air pockets. Continue to fill until the soil is level with the surrounding ground, and water again. Add a little more soil as it settles into the roots to form a small mound around the trunk.
Create a water ring with soil 2 feet from the trunk, 4 inches high and thick. Fill the ring immediately after planting. Water every 3 days for two weeks and once a week for two months thereafter. The ring will have disappeared by then. Continue with deep watering about once every 10 days, depending on rainfall.
Fertilize with a citrus tree fertilizer only after you start to see growth. Follow the manufacturer's directions for the amount to apply, depending on the age and size of the tree.
Keep lawn grass and weeds at least 2 feet from the trunk of the tree. Mexican lime trees do not compete well with weeds and grass for water and nutrition. Use a contact herbicide, or hand-pick the weeds from the soil. If using herbicide, don't allow it to touch the tree.