Garden Column for the Salisbury Post
Darrell Blackwelder
January 24, 2002
Landscape
maintenance contractors often use this time of year to apply mulch. Mulch can be as
much a design element as plant materials. Now is an excellent time for homeowners to add
new or replace old mulch.
Mulch helps to insulate
plants and conserves moisture reducing water consumption and preventing loss of plant
material during hot, dry weather. Organic
mulches also enrich the soil and in many instances prevent lawn mower and trimmer
damage. Mulches also reduce weed competition and often prevent some weed seed
from germinating. But, mulches will not
prevent or delay weed growth forever.
Pine needles, bark
nuggets, ground limbs, twigs and wood shavings are popular organic mulching materials.
Mulching material containing green wood or cellulose attract termites including
ground limbs, sawdust, twigs etc. attract termites. Pine needles, bark nuggets and
composted material do not have viable cellulose that attracts termites, however, freshly
shredded limbs, twigs
and sawdust do attract termites. Those who
use this type of mulch around foundation plantings should be aware of possible termite
problems.
Mulches should be applied 3 to 4 inches deep over clean, weed
free soil. Excessive applications of fine mulch create problems with oxygen penetration
for root growth and potential water problems. I have observed mulches up to 12 inches deep
in some landscapes. Over mulching can cause serious problems with root development. Heavy
applications of fine mulch such as sawdust and finely ground bark inhibits oxygen uptake
of trees and shrubs.
Grass clippings create a "thatched roof
effect" prohibiting water penetration and create drought stress in some plantings.
These materials and any other “green” material should be composted before using
as a mulching material.
The ground around plant materials to be mulched should bare and
free of weeds before mulch is applied. Pre-emergence herbicides prevent germination
of weed seeds and should be applied in early spring and fall over the top of mulch.
Mulch often carries weed seed and can be controlled with a pre-emergence herbicide
over top of the mulch. When using
pre-emergence herbicides, always read and follow directions carefully.
Landscape fabric or geo-textile material placed under the mulch
retards and prevents germination of some weed species. This material will not prevent
growth of Bermuda grass. Bermuda grass, nutsedge and other perennial weeds or grasses must
be eliminated before applying geo-textile material.
Never use black plastic as mulch. Black plastic either
allows too little water or excessive amounts
of moisture to accumulate in or around the root system. There is practically no oxygen
penetration for root growth which is extremely important to root growth and development.
Trees and shrubs often do poorly when black plastic is used under a layer of mulch.
Many weeds such as bermuda grass easily penetrates plastic creating a nightmare to
maintain.
Other materials such as crushed
brick, gravel, lava rock, or pebbles can be successfully used as mulching material if the
sure the materials are compatible with the design. These materials are often used in
commercial situations to reduce fire hazards from smokers. However, many landscapes are
not compatible with use of these materials. Inorganic materials in many landscape
situations, require ground cloth or some geo-textile material to prevent red mud or
other soil types from staining the material.
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