Roots – Back to basics
The majority of avocado roots are usually found in the top 30cm of soil. Feeder roots dominate the shallow root system with new healthy roots being white or pale yellow in colour and older thicker roots being darker and more woody in appearance. Feeder roots vary in thickness but are often much more brittle relative to other roots present in the soil and lack root hairs.
Avocado roots prefer loose well aerated soils with roots often found in or just below mulch layers. They naturally flush and die back and it has been shown in New Zealand that root flushes can occur throughout the year if conditions are suitable.
The shallow root systems means periods of prolonged or heavy rainfall can leach nutrients away from the majority of the root mass capable of taking them up. They are also very prone to damage from periods of flooding or excess soil moisture due to a lack of oxygen.
Phytophthora cinnamomi is the major root rot pathogen with root tip die back often visible on infected roots in the form of dark necrotic lesions starting at the tip of young roots.
For more information on how to maintain a healthy root system refer to the tree health chapter of the grower manual.