I saw it just today, landscape crews hard at work mulching trees, or should I say over-mulching trees. Mulch is piled against the trunk of the tree rather than spread out in a thin layer. This method of mulching, often referred to as "volcano" mulching slowly impacts tree health and vigor. Trees would be much better off having the same amount of mulch spread out across a larger area. This would promote proper root growth and tree vigor. Below is a news release from one of my colleagues Vinnie Cotrone, Extension Urban Forester, addressing this issue.
Epidemic Effecting Landscape Trees
There is an epidemic spreading
throughout the state and country that is slowly killing trees and shrubs in our
landscapes. No, it isn’t another disease
or insect we accidentally imported from another country like Asian Longhorned
Beetle which is killing trees in NYC and Chicago or Dutch Elm Disease which
changed our landscapes in the 1960’s and 70’s.
And unlike some of these imported pests, this epidemic can be prevented
very easily.
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| Don't over-mulch and create mulch "volcanoes!" |
This epidemic is caused by
misapplication of mulch around our trees and shrubs. “We are over-mulching our trees and shrubs to
death” says Vincent Cotrone, Penn State Urban Forester and certified
arborist. “Mulching is a terrific way to
add organic matter and nutrients, conserve soil moisture, and prevent lawn
mowers from injuring trees and shrubs, but it is just being put on way too thick
and piled too high on trunks and stems.”
When mulches are put on too thick
and piled against the stems of trees and shrubs, they begin to suffocate roots
and create a moist environment in which opportunistic decay fungi such as
Phytophora, Armillaria, and Leptographium attack the trunk and roots, causing
root rots, a decline in plant health, crown dieback, and tree failures. Besides causing the roots and stems to rot,
over-mulching prevents the movement of oxygen and carbon dioxide in and out of stems;
can lead to rodent chewing and stem
girdling; nutrient deficiencies and the production of toxic organic acids; and often causes roots
to grow up into thick mulch, only to dry out in hot summers, or form girdling
roots that encircle and the trunk.
“It seems to be fashionable these
days for landscapers and homeowners to create these mountainous mulch
“volcanoes” at the base of trees” says Cotrone.
“Unfortunately this continues because there is a lack of knowledge about
how trees really grow and the harm caused by this practice.” A quick walk in the woods will illustrate how
trees have a natural flare where their trunks meet the soil (visible even on
young trees). “It is important that we
not cover that flare with soil or mulch” says Cotrone. “Spread the mulch out in a layer that is no
thicker than 3-4 inches, and don’t pile it up on the trunks of trees and stems
of shrubs”.
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| A properly mulched tree! |
Mulching your trees and shrubs can
improve soils and grow healthy plants, but too much of a good thing can be
harmful. So take a closer look at your
mulch or your landscapers work this summer and make sure you don’t have
mulch-mountains or “volcanoes” in your landscape. Let’s stop this epidemic before it kills more
trees.
For
more information on mulching visit the following websites:
Penn State Extension: Planting Ornamentals
Trees Are Good: Proper Mulching Techniques
