How to Mulch and
How Not to Mulch
Correct mulching around the base of your trees can be very beneficial to
the health and appearance of your trees; improper mulching can severely
damage and open your trees to invasion by insects and disease.
Trees growing in natural untouched settings, such as forest preserves,
have their feeder roots, which are located in the top 6 to 12 inches of
the soil, anchored in well-aerated soil full of essential nutrients. The
forest floor is covered with organic matter such as leaves and fallen
twigs. These decaying natural materials replenish nutrients and provide
an optimal environment for root growth and mineral uptake.
Landscapes in residential areas and yards have poorer soils, little
organic matter, competition with grasses for moisture and extreme
changes in soil temperature. Applying a 2 to 4 inch layer of mulch
around the base of a tree can provide a more natural environment and
improve tree health.
When to Mulch
Mulch can be applied any time of year when trees or shrubs are planted.
The best time to apply mulch around established trees or bed areas is
mid-spring, when soil temperatures have warmed up enough for sufficient
Mulch should be applied 2-4 inches in depth over relatively clean,
weed-free soils. Mulch should be no more than 2 inches if soil is not
well drained; up to 4 inches if drainage is good. More finely textured
mulches should be no thicker than 1 to 2 inches. Never pile mulch more
than 4 inches high. Do Not allow mulch to touch tree
trunks; keep mulch 3-5 inches away from trunks of young trees and 8-12
inches from trunks of older established trees.
Types of Mulch
There are mainly two types of mulch organic and inorganic. Inorganic
mulches include various types of stone, lava rock, rubber chippings and
other materials. Inorganic mulches do not decompose and do not need to
be replenished often. Inorganic mulches, however do not improve soil
structure, add organic materials, or provide nutrients. Organic mulches
include wood chips, pine needles, hardwood and softwood barks, cocoa
shells, leaves, compost mixes, and a variety of other products usually
derived from plants. Although most organic mulches decompose faster and
must be replenished often, the decomposition process improves soil
quality and fertility.
Benefits of Proper Mulching
-Helps maintain soil moisture.
-Reduces the germination and growth of weeds.
-Serves as nature’s insulating blanket. Mulch will keep soils warmer
in winter and cooler in summer.
-Improves soil aeration
-Can inhibit certain plant diseases.
-Can improve soils fertility
-Gives planting beds a uniform, well cared for look.
Problems Associated with Improper Mulching
-Mulch exceeding 4 inches around the root zone can stress the tree
causing root rot.
-Piling mulch against the trunk or stems of a tree can stress stem
tissue, and may lead to insect or disease problems.
-Thick layers of fine mulch can become matted, and may prevent the
penetration of water and air to the root zone.
-Deep mulch provides hiding places for rodents that can chew
extensively on the bark around the trunk.