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Mulch Volcano Madness! | Environment

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Mulch Volcano Madness!
Mulch Volcano Madness!

Excessive Mulching Kills Trees
June 14, 2011 

Spring is in the air, along with the appearance of a deadly perennial threat to the health of trees everywhere.  It is not an insect, nor is it a disease.  It is not a new and exotic scourge that has invaded our borders from some far off region of the planet.  No, it is much worse than any of these.

It is... the deadly mulch volcano.

This crime against arboriculture is annually perpetrated by “professional” landscapers and well-meaning homeowners who follow their example.  Each year, literally tons of mulch are piled high against the trunks of trees everywhere... and it’s killing them.

To some, this pile of mulch may look neat and tidy, but unfortunately it results in the slow decline and eventual death of the tree.  But what’s really maddening is the fact that people pay good money to “professional” landscapers to do this. 

Folks who care enough about their property to entrust it to a landscaper should be applauded.  They do so with the intent to keep it neat and well-maintained at a professional level. 
By the same token, many of those well-intentioned property owners are in essence paying good money to have someone kill their trees.  Trees are an expensive investment by any standard, and those who “professionally” maintain them should know better.  It’s their reputation on the line.

Further, the damage done by these poor examples of “professional” landscaping extends to the unsuspecting do-it-yourself homeowner.  They look to these “professionals” for a model of good practice.  Instead of a good example to follow, they unwittingly get irreversible damage to their landscape and their investment.  

A local homeowner recently told me that he “assumed the way landscapers mulched was the right way.”  Fortunately, he did some research on the internet and discovered that mulch volcanoes are very bad indeed!

“Mulching is a great practice,” according to Dr. Nina Bassuk of Cornell University.  “It keeps weeds down, moisture in the soil, and keeps weed whackers from damaging tree bark.”

Dr. Bassuk is program leader of the Urban Horticulture Institute at Cornell University, and co-chair of the Cornell Community Forestry Work Team.  She also sits on the board of the New York State Urban Forestry Council.

“Mulch should be 2-3" deep and not touch the trunk at all,” warns Dr. Bassuk.  “A nice wide radius of 3-4' for newly planted trees is sufficient.”

For young, newly planted trees, sufficient moisture during the first years after planting is critical. Because mulch volcanoes actually starve tree roots of water, many trees send roots out into the mulch pile, searching for badly needed moisture.

The deadly result is a tangled mess of girdling roots that are drought stressed, will stunt tree growth and eventually kill the tree.

Andrew Pleninger is Vice-President of Urban Forestry, an urban forestry and arboricultural consulting service to communities and clients in Western New York. Prior to forming Urban Forestry, LLC Pleninger was City Forester for the City of Rochester, NY for 10 years.  He received a B.S. in Natural Resource Management concentrating in Urban Forestry from Colorado State University.

Pleninger states, “Like many practices in life, a little mulch is a good thing and too much mulch is a bad thing.  Mulch piled against the tree trunk (volcano mulching) leads to the growth of advantageous roots into the mulch surface when it is damp.” 

These roots grow across the root ball, around the trunk, and literally strangle the tree to death. 

In examining a small mulch volcano over the weekend set in place by a well-meaning homeowner on a village tree, I found that even this miniature mulch volcano was causing disastrous effects. 

Small roots were already growing up into the mulch in a tangled mess across the root ball.  If left alone, the web of surface roots would have certainly caused a slow death for the tree.  

Pleninger goes on to say, “As the mulch dries out in the hot sun water is ’sucked’ out of the tree through these roots, desiccating the tree.  Three inches of mulch around the base of the tree but not touching the tree trunk helps retain moisture in the soil. It also reduces potential damage to the tree trunk by the lawnmower and string trimmer.”

Mulch volcanoes cause the most problems for young trees. When newly planted trees are subjected to excessive mulching, moisture can’t penetrate the mulch and reach the root ball, even if the area is irrigated heavily. These trees struggle to establish and, as a result often die within five years of planting. 

This is often seen in commercial developments where landscapers are hired to maintain the grounds.  What begins as a beautifully planned landscape on a commercial site, ends up as an eyesore with stunted, dying, and dead trees.

Jack Feltz is a Senior Forestry Supervisor and Arborist for National Grid.  He terms mulch volcanoes a “significant industry concern.” 

Said Feltz, “What I believe frequently happens is people like the looks of ‘new’ mulch and they forget to pull the old layers off before putting the new down.  After a couple of years you have built up ‘volcanoes.’”

And, like Bassuk and Pleninger, Feltz also states, “The (root)flare of the tree should always be exposed to the air.”  Never pile mulch against the root flare and tree trunk. 

Correctly applying mulch to a tree is not rocket science.  Apply a good organic mulch in a circle covering the entire root system of a tree.  The general recommended mulching depth is 2-3 inches.  Keep mulch at least 6 inches from the base of the tree trunk.  Water regularly, but do not over water.  Just keep the mulch and soil moist.

Maintain this method of mulching on your tree along with providing sufficient water, and you’ll be rewarded with vigorous, healthy growth, and a tree that will provide generations of beauty and enjoyment.

For more information on proper methods of tree mulching, what kinds of mulch to use,  and trees in general, visit these web sites:

Village of Medina Municipal Tree Board

Cornell University Urban Horticulture Institute

Urban Forestry, LLC

Ask This Old House: You’re Killing Your Trees with Too Much Mulch



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