Soil Moisture Control for Hass Avocados

Irrigation Selection

• Because avocados thrive in full sunlight, their soil can quickly dry out without proper irrigation strategies; fruits abort or fail to develop at all without ample moisture. With their shallow root system only diving as deep as 6 inches, you should use a drip irrigation system around your trees and out to the drip line. Drip systems seep water from hoses laid on the soil for consistent moisture. These evergreens use more water between spring and fall with little absorption during winter. Avoid waterlogging the roots with high-pressure sprinkler systems; roots quickly rot with severe tree dieback.

Mulch

• Spread organic mulch around your trees to conserve soil moisture; you also add critical nutrients to the soil as the mulch decomposes. Maintain a mulch-free zone 6 inches away from the trunk as you cover the ground out to the drip line and slightly beyond. Your avocado tree trunk should remain bare and dry to avoid rot. A 4-inch layer of mulch is sufficient to allow water and air exchange between the soil and atmosphere -- a thicker layer creates a barrier to natural resources and causes root stress. Mulch also creates a physical barrier to spreading turfgrass. Competing grass roots may hinder moisture uptake for your tree if the turf grows under the canopy.

Soil Moisture Meters

• If you want a more accurate soil moisture control strategy, insert electronic moisture meters in the soil surrounding your trees. These devices use safe electrical pulses to read moisture levels; check them daily to schedule your watering sessions. You can even attach them to an automatic irrigation system if you cannot tend to the trees daily. Once the meter indicates dry conditions, it signals your watering system to turn on until the soil is damp. This moisture control choice prevents both under- and overwatering if it is calibrated and installed correctly.

Considering Whitewashing

• Whitewashing avocado tree trunks allows you to prevent bark sunscald during the winter. However, it is also a moisture control strategy for the trees' vascular system. As winter sun strikes one side of the tree, its vascular system becomes active and requires soil moisture; other cold tree sections remain dormant and do not pull moisture from the ground. Using whitewash across your bark creates a uniform trunk temperature as sunlight reflects off the light color. Your tree's vascular system remains dormant and does not pull excessive moisture into the limbs until spring arrives with warmer temperatures.