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QUESTION: we have a 12 foot around black maple in our backyard and all but the last 5 years we were covering old mulch with new mulch every spring. we now have a 2 foot high hill around the tree that has tiny roots showing through dirt and old mulch. can we dig up the hill without hurting the tree or is there another suggestion for this area. also my dogs chase squirrels up this tree all day long

ANSWER: Are you saying the mulch pile is two feet deep?

This is not a good idea, and it will cause adventurous roots to grow.

You should never have mulch deeper than a few inches over the critical root zone, but will await your reply before I suggest or comment further, as do not want to go down paths which are only based upon assumptions.

Do you have any photos?


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QUESTION: we have not put any new mulch on in over 5 years, the pile is about 18 inches high and when ive picked through it in the past ive noticed that it is mostly dirt and some moldy old mulch. as i mentioned previously there are a lot of string like roots all around the tree

Well mulching, especially organic mulch is a great idea.   In fact is one of the best things you can do for your trees!

Many of the benefits, as you likely know are the increase in soil organic matter, increased water holding capacity, available nutrient increase, insulator from heat or cold allowing a buffer over the root zone, an effective control of weeds and a good way to keep lawn equipment away from trunk area.

However if done incorrectly can actually cause the death of a tree!  

So what are the rules, and how do we fix.   First rule is never too much.  Maximum should be two to four inches.

Unfortunately, many landscapes are over mulching, to the point the term "volcano mulching" has emerged.  

Some mulches last longer than others, but the replacement rate should never exceed the decomposition rate.  Why do landscape companies over mulch?  To bring back the color, or to create a more effective weed control are likely reasons.  Deep mulch can be an effective weed control, but can lead to other serious issues, so how do we fix.

We can not use spades, shovels or rakes.  But the mulch level should be taken down.   If you have 15 inches, I would suggest taking it down to a fairly low level, which will be likely unsightly and need a new fresh mulch on top for visual appeal.  

With this much mulch, it may be impossible to do by hand.  But if you wish to try, use gloved hands to remove mulch from the base of the tree, exposing the root flare (the area where the roots turn out and away from the tree).

As mentioned, do not use a rake or shovel, as this can damage delicate roots.

If removing these maniy years of layered mulch by hand is too difficult, then you will need to find and hire a tree care company that can use an air spade to remove the mulch by using high volumes of air flow.  This is an effective method of moving soil with no damage or minimal damage to root area.   You will find most of the full time tree service companies have air excavation tools to assist.

Remove the old mulch, and reapply new, to a depth of not more than around four inches.  


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Robin Wells


Most of my experience is in urban forestry and landscape environment. Questions related to tree identification, tree diseases or insect related problems, soil related issues or soil science, pruning techniques or practices, pesticide related questions, fertilization of trees or shrubs, tree support systems (cabling or bracing), tree planting, tree watering needs or tree risk assessment/management, although insect related we also have a specific area dealing with the emerald ash borer.


30 years work in urban forestry. Bachelor degree in forestry. ISA Certified Arborist. ISA Certified Tree Risk Assessor. Consulting Arborist. Ontario licensed pesticide applicator.

ISA Intrenational ISA Ontario Ontario Commercial Arborist Association Tree Care Industry Association American Society of Consulting Arborists

Midland Mirror ( newspaper )

Bachelor degree in forestry. Many other post university seminars and courses in Aboriculture.

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Various commercial, residential, municipal, real estate and legal clients. Typically do not list the names.

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