The avocado tree, or Persea Americana, originated in Mexico and now grows throughout Central America, the southern United States, the West Indies and parts of the Middle East and New Zealand.
Avocado trees grow best in a loose soil made up of sandy loam or decomposed granite. Excess moisture can damage plants, and as a result the best soil for avocado trees should drain well. Leaves and wood chips placed on the top of the soil protect roots against overheating and provide nutrients to the avocado tree.
Avocado trees tolerate acid and alkaline soils but prefer a soil pH between 6 and 6.5. A pH below 6.2 increases the likelihood of phytophthora root rot. Gardeners with soil naturally lower than 6.2 can raise the pH by adding calcium carbonate.
An excess of salt in the soil causes avocado leaves to turn brown. Salt can be cleared from the soil by watering slowly and deeply. For potted plants, irrigate the tree until water runs out the holes on the bottom of the plant for several minutes. Water plants in the ground by dripping only 1/2 gallon per hour for several hours.