The avocado tree is a species of tree native to the Caribbean, Central and South America. The tree produces a popular fruit with a rich flavor and buttery texture that is used in salads, dips and soups. Avocado trees can grow up to 80 feet in height when planted in their native soil under ideal conditions. They are also a popular house plant that can be grown from their egg-like seeds. Yellow leaves on an avocado tree are a sign of a deficiency in the plant's care.
Examine the leaves to determine the way in which they are yellowing. Specific yellowing behavior is indicative of specific problems. For example, if the leaves turn yellow while the veins remain green, this is an indicator of iron deficiency, while overall yellowing may be caused by nitrogen deficiency.
Check the soil's moisture level with the probe of a moisture meter by inserting the meter's probe into the ground or the potted tree. Then read the moisture level on the meter's read-out screen. Leaves that turn yellow and then eventually brown may not be getting enough water.
Apply chelated iron to the root zone if leaves turn yellow with green veins. This type of yellowing behavior is indicative of an iron deficiency. To do this, purchase chelated iron from a garden supply store. Mix chelated iron with water according to directions on the chelated iron packaging. Then spread the water around the drip-line of the tree. Mixing directions will vary depending on the chelated iron brand.
Add a nitrogen-based liquid fertilizer to the watering supply for avocados if the leaves are light-green. Leaves that turn yellow in this way are an indicator that the plant is low on nitrogen. To do this, purchase a nitrogen-rich liquid fertilizer from a garden supply store.
Mix fertilizer with water according to directions on the fertilizer packaging. Then spread the water around the drip-line of the tree. Mixing directions will vary depending on the fertilizer brand.
Water once weekly by turning a garden hose onto the ground in different root zones each time. Keep the hose on the ground until approximately an inch of standing water is on the ground, and then allow the water to soak in.
Allow ground to dry out between watering, and skip watering during rainy periods. Your soil should never feel like a saturated sponge. Watering in this way will help keep down the growth of cinnamon fungus. Signs of cinnamon fungus include leaves that fade to a pale green and droop, sparse foliage and dieback of branches near the top of the tree.