Now let’s look at some of the additional benefits that can be achieved by using organic mulches as opposed to non- organic varieties such as gravel or pebbles.

  • Over time the breakdown of organic material adds valuable nutrients and trace elements to the soil that are required for tree growth.
  • This gradual breakdown of the material also improves soil structure and aids in drainage, which in turn provides an environment which is more conducive to tree root growth.
  • The addition of organic material promotes soil micro-organism activity. This in turn supports an increase of beneficial organisms within the soil environment such as earthworms.
  • So now we have a basic understanding of the general benefits garden mulch can provide, how do we choose which path to go down? Generally speaking, it is my opinion that non-organic mulches provide a more uniform, consistent and formal appearance. Obviously leaf mulch spread around a Japanese water garden would look out of place, as would river pebbles in a large open garden bed full of mature established trees.

Clearly we need to consider the specific application and the desired final outcome in order to reach a sensible decision about which mulch we should use. So now you have the general information required to make the preliminary decision of what type of mulch to use, let’s look at the do’s and don’ts of how to apply the mulch.

What you should do:

  • Always apply the mulch to a depth of between 75 to 100 mm. At this depth weed suppression is achieved and moisture retention is optimised.
  • When applying mulch over the root zones of trees, always cover as much of the zone as possible. As a rule of thumb, the drip line of the trees crown provides a reasonable guide that will benefit tree health, but as large an area as the environment will allow should be covered, as tree roots grow well beyond the drip line of the trees crown.

What you should never do:

  • Never apply the mulch directly around the base of your trees and shrubs. As the decomposition process begins this can cause collar rot which often results in the death of the tree or plant. (See image)
  • When using organic mulches, live green materials should generally be avoided, as these can extract nitrogen from the soil as decomposition begins.

HAPPY MULCHING!

About the author: Dave is a qualified, experienced and passionate arborist working with the awesome team at Brisbane Tree Experts. “We care about your trees living”. And we hate seeing piles of grass clippings around the stems of trees!