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Organic Mulches
By Michigan State University - Extension
Apply
an organic mulch on most established ornamental
plants
in mid-spring when the soil has
warmed sufficiently
for
active root growth. If applied
before this time, the mulch will keep the ground cool and root growth may be retarded. Apply an organic mulch around newly set ornamental plants after they
are put into
place
and thoroughly watered.
How
Deep to Apply Organic Mulches
For
best results, apply mulch at least 2 to 4 inches deep
over
the whole area anytime during spring, summer or early fall
but
avoid covering the crowns of very low-growing
ornamental
plants. Tender ornamentals that
need winter
protection
may require an additional 1 to 2 inches of
mulch
around the crowns or bases of the plants during the
winter.
In the spring, this added mulch should be fanned
out
or away from the stems or crowns of the plants before
more
material is added for a summer mulch.
Fertilizing
Organically Mulched Plant Material
As
indicated previously, mulching with many organic
materials--including
wood chips, sawdust, straw or
shredded
bark--means you must apply extra fertilizer
around
the plants to reduce the chance of nitrogen
deficiency
or starvation. Apply 1/4 pound of
ammonium
nitrate
or ammonium sulfate for each bushel of mulch
material
used on the bed, or 2 pounds per
100 square feet
of
a complete fertilizer such as 5-10-5, 12-12-12 or
similar
analysis. This fertilizer should be
applied
before
the mulch is placed on the soil, or in early spring
before
more material is added to plants already mulched.
If
the lower foliage yellows and the plants lack vigor
during
early summer, apply additional fertilizer.
Do
Not Over mulch
The
roots of plants need a constant supply of oxygen at
all
times. Over mulching kills the roots
of shallow-rooted
plants
by suffocation.
Symptoms
of too much mulch include chlorotic foliage
(symptoms
often resemble iron deficiency), abnormally
small leaves, poor growth and dieback of older branches.
Disease organisms that are active under conditions of low oxygen and excessive moisture can become active and
attack rotted as the plant tries to send out new roots into the mulch layer. Excessive amounts of mulch applied around tree trunks can lead to
cankers on susceptible species.
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