Dispelling the Myths of Mulch

  • Jan 10, 2019

In light of California’s recent bouts with drought and excessive heat, California avocado growers should give serious consideration to using organic mulch in their groves.

Research indicates that organic mulches that consist of coarse woody material are best — and can be created from the chipped leaves and branches of trees. The most effective mulches are coarse (1/2” or more in diameter), applied as soon as possible after chipping and applied at a depth of about 4”.

Mulch provides a number of benefits:

  • Moderates soil temperature
  • Conserves water
  • Reduces soil compaction
  • Provides nutrients and reduces the need for pesticides and fertilizers
  • Provides a habitat for beneficial insects
  • Controls weeds, disease and non-beneficial pests

A recent blog post from the University of California farm advisors addresses myths that often deter growers from using mulch. Below are mulch myths relevant to California avocado growers.

  • Mulch does not draw nitrogen from the soil unless it is incorporated into the soil.
  • Wood chip mulches, even from diseased trees, will not transmit root pathogens such as Phytophthora and Armillaria root rot to healthy tree roots. When chips are stored in a pile for a few days, microbes attack pathogens and severely reduce their numbers. If diseased chips are incorporated into the soil, there is a rare chance they could infect the tree’s roots.
  • Wood chips do not change the pH of the soil.
  • Wood chips do not lend themselves to tunneling and, in fact, tend to harbor beneficial insects and species that help control pests.