Using Organic Mulches
Apply an organic mulch on most established ornamental plants in mid-spring when the soil has warmed sufficiently for active root growth.
Using Organic Mulches
By Michigan State University - Extension
When to Apply Mulch
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 the roots. Sometimes the old root system will be
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.