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Why improperly installed mulch around a tree in landscaping beds has consequences. Cipriano Landscape Design- Northern, NJ


Have you ever been driving around and seen a tree on someone’s front yard with a huge dome of mulch surrounding its trunk? This dome of mulch is what is referred to as the mulch volcano. Some homeowners, and even contractors, believe that a pile of mulch will protect the tree, but in reality what it does is slowly kill it overtime. It’s important to know about proper mulching techniques so you can properly care for the plants and trees in your yard.

The root flare is the part of the tree where the trunk begins to spread out to meet the roots. Root collaring occurs when this critical portion of the tree is either planted too deep in the ground or covered up with too much mulch.  When this happens the roots that enjoy being near the surface will begin to grow upwards in order to seek proper oxygen levels. The roots can actually end up circling the trunk of the tree, which is called girdling and causes strangulation that kills the tree over time.

There are other problems for the tree that too much mulch around the trunk will cause. The bark of the tree is the outer most layer of protection from the living inner portion of the tree. The bark of the tree needs to breathe and get air, and by adding mulch you are preventing the tree from doing that. Too much mulch also creates moisture around the bark which in turn weakens it. A weakened bark is in an invitation for insects and rodents to come and feast, and what is worse is they have a nice dome of mulch to hide in from predators. Mulch can also be home to bacteria, viruses and fungi which normally break down the mulch over time.

How to fix collaring:

Examine a tree and see if the flare is visible.

Gently remove the mulch by hand until you locate the flare.

If all the mulch is removed and you still haven’t found the flare, use a trowel or hand shovel and gently remove the soil around the trunk until the flare is exposed.

Remove a 6” wide swath of dirt around the trunk exposing more of the flare, which will allow more air to circulate around the trunk. You can fill the trench with lava rock to prevent excess water build up next to the trunk.

If you hit a significant amount of fibrous roots stop at once, this is girdling and if you remove or damage a significant portion of the fibrous roots the tree may go into shock and die.

I would suggest contacting a certified arborist or a professional familiar with air spading. Air spading is a technique that removes the dirt with a high-pressure air nozzle without damaging the roots.


Once you know all your tree flares are properly exposed you can safely re-mulch the planting beds. When installing new mulch, never cover up the tree flare or put any mulch around the base of shrubs. Poor mulching is a sign of inexperience and a lack of professionalism if it’s a contractor. Unfortunately it happens all too often on residential landscapes. Mulching is important throughout your yard because it has many benefits like keeping the soil cool and retaining moisture, but if it’s done incorrectly it can end up killing your plants.