Double Shredded or Wood Chip Mulch?

Why Mulch at All?

          Mulch has many positive benefits for the health of your trees.  Trees in the forest produce a large volume of mulch naturally, but it’s rarely done effectively in the urban environment.  Leaves, twigs and branches, and other organic matter drop to the forest floor and recycle nutrients back into the soil over the root zone.  Soil in the forest contains the nutrients and organisms that are essential for optimum tree health.

       Good soil contains much more than just the proper level of nutrients.  Good soil has to function properly.  There is an important balance or “ecosystem” that works together to keep the soil operating correctly.  It starts with a good source of organic matter.  That organic matter is broken down by organisms that include, among other things, worms and micro-organisms.  As the organic matter is broken down, the process naturally aerates the soil which helps to alleviate soil compaction.  It also releases available nitrogen for easy absorption by the root system.  

Good soil also contains mycorrhizae.  Mycorrhizae is a naturally occurring fungus that attaches to absorbing root hairs in a symbiotic relationship.  It spider-webs out into the surrounding soil, increasing the absorbing capability of the roots hairs by up to 100 times.  The natural mulching process in the forest is the ideal habitat for mycorrhizae to thrive.

Other benefits of mulch include moisture retention.  Mulch holds moisture in the soil during droughts.  It also regulates soil temperature, keeping roots at the proper temperature throughout the year.  It reduces mechanical damage to roots and trunks from lawn mowers and weed wackers.  These devices often cut through the bark into the vascular system, disrupting the vascular flow of water and nutrients.  The cuts also become openings for pests and diseases to breach natural defenses and attack the tree.

As beneficial as mulch can be, improper mulching can be worse than no mulch at all.  Initially, mulch should be spread in a 2-4 inch layer over the root zone, but should not come in contact with the root flare.  That can cause moisture to become trapped against the trunk and lead to trunk rot.  It also can become the perfect environment for harmful insects to flourish in close proximity to the trunk.

Wood chip mulch is much better than the commercially available double-shredded mulch.  Wood chip mulch is larger and heavier.  It breaks down slower, so it last longer.  Double shredded mulch can matt down and create an impermeable glaze that keeps water from penetrating into the soil.

A new layer of mulch can be added every year or so, but only one to two inches deep, depending on how much remains from the previous application.  The old mulch should be turned with a hard rake first, then the new layer placed on top. 

     As a service to our local community, Growing Earth delivers free truckloads of woodchip mulch when we’re working in your area.  Click here or call our office for details.