1st If you are mulching to increase the health of your soil than bark mulch
may not be the way to go. Bark mulch is made up of outer bark of trees.
Outer bark of trees is made up of suberin. Suberin is long chains of fatty
acids. There is not a suitable carbon source available to help feed the
soil. Composted wood chips and leaves would be suitable to increase soil
health by feeding the soil. I say composted because fresh chips (from
symplast maintaining trees) has protoplasm spread all over the place. This
attracts micros that attack defenseless cells of your trees. Once the chips
are composted this is not an issue. Also the more you compost the chips the
less chance you will have of getting an undesired fungus on your house. I
have had good results with cutting the turf low with a weed wacker (KEEP
AWAY FROM YOUNG TREES) and placing the composted wood chips on top at about
4" in depth and flat. Contacting a tree company may lead you to some nice
composted wood chips.

"Suberin is a lipid that in the outer periderm of phellem waterproofs outer
bark. Suberin- impregnated phellem is called cork. The chains of carbon and
hydrogen in suberin are so varied that few enzymes from microorganisms are
able to cleave it for an energy source. This characteristic gives corks
their unique benefits for sealing bottles. Suberin is also in a layer in
absorbing roots called the Casparian strip. This layer is an effective
boundary essential in the absorption processes. Energy is required to
transport water and elements through the boundary into the tree. Suberin is
also a major compound in the barrier zone that forms after wounding. Outer
bark that contains suberin is often used for mulch, since bark mulch will
not be broken down by soil microorganisms because of the suberin. The bark
mulch has aesthetic value, but the bark is of little value for providing
energy-releasing compounds to soil microorganisms. Some trees store fats and
oils as their reserve energy source. The fats and oils are not soluble in
water. Many palms store oils. Waxes on leaves and fruits are also lipids."
Source http://www.treedictionary.com/DICT2003/shigo/CHEM.html


If you contemplate using chemicals to kill the grass you may desire to read
up of pesticides.
http://home.ccil.org/~treeman/spring.html


Sincerely,
John A. Keslick, Jr.
Arborist
http://home.ccil.org/~treeman
and www.treedictionary.com
Beware of so-called tree experts who do not understand tree biology.
Storms, fires, floods, earthquakes, and volcanic eruptions keep reminding us
that we are not the boss.

wrote in message
oups.com...
We would like to apply bark mulch in several areas around our home
where grass currently exists. Is there a need to get rid of the grass
before applying the mulch, either by lifting the sod or laying
cardboard and four inches of soil, as we do when preparing a new bed,
or can we just lay landscape fabric and 2-3 inches of mulch and that
will take care of the grass over time.
thanks
Teresa