MULCH FOR TREE HEALTH
Research done at the Morton Arboretum in Lisle has shown that when
grass roots and tree roots compete for water and nutrients, the grass
always wins! If you remove the grass from around your trees and replace it
with an organic mulch, the tree quickly starts producing more roots. But,
be careful because over mulching is rapidly becoming the number one cause
of death to shrubs and trees.
Why? Because too thick a mulch (over two inches) suffocates plant
roots. Roots must respire and take in oxygen. When oxygen levels in the
soil drop below 10%, root growth declines, and soon the plant dies also.
Problems from over mulching accumulate slowly and it may take three to
five years for the damage to show. When mulch is placed against the stems
and trunks of trees more damage is done. Roots can survive continual
moisture; but, tree trunks can not. This contact of mulch and trunk causes
the trunk tissue to decay and fungal and bacterial disease to develop.
Many times bark beetles and borers will assist in the decline of the tree.
The continuous use of the same type of mulch can change the pH of the
soil. Monitoring the soil and rotating the type of mulch used can be a way
to correct any pH problems. Placing piles of mulch against a tree trunk
will provide cover for small rodents. They will live in the mulch and chew
on the tender nutritious inner bark to get at the sugars. Many fresh and
non-aged mulches may cause nitrogen deficiencies. Bacteria and fungi which
break down the mulch must have an ample supply of nitrogen to do their
job. They use up the nitrogen in the soil.. Some experts suggest when
using wood chips that you add a high nitrogen fertilizer to the mulch.
Types of Organic Mulch
Grass Clippings: Dry or compost before using and mix with other
materials to reduce matting.
Hardwood Chips: Apply a nitrogen fertilizer. (see above)
Composted Leaf Litter: This is an excellent source of natural
Manure: Compost before using and mix with coarse textured
materials to avoid burns.
Mushroom Compost: This is readily available and a good source of
Peat Moss: It is not recommended because it packs down and dries
Pine Boughs: This is a very good covering for perennials in
Pine Needles: This is good for providing acid, but should be
mixed with other materials.
The use of organic mulches mimics the natural processes that occur in a
deciduous forest where a blanket of leaves is deposited on the forest
floor every fall. Leaves insulate the soil during winter and are the
mechanism by which carbon and mineral nutrients are recycled through the
NEW TREE AND SHRUB HANDBOOK IN LIBRARY
The Illinois Department of Natural Resources, and the U.S. Forest
Service funded a project to donate a copy of the Tree and Shrub Handbook
published by the Morton Arboretum to each Tree City in Illinois. Our copy
is in the Palos Park Library. It is a part of the Tree Body Resource File
and can be used by any library patron. This is a loose leaf notebook with
material on a wide variety of topics about the selection, and care of
trees and shrubs, including pests, diseases, planting, pruning, and other