Most Homeowners Turn Their Trees Into Ticking Time Bombs With This One “Helpful” Landscaping Practice

Walk through any suburban neighborhood and you’ll see them everywhere: neat, volcano-shaped mounds of mulch piled high around tree trunks. Most homeowners believe they’re doing their trees a favor by applying thick layers of mulch, but this common practice is actually one of the most damaging mistakes you can make. What looks like careful tree maintenance is slowly killing trees across America—and most property owners have no idea.

The Deadly Art of “Volcano Mulching”

A mulch volcano is when mulch is piled against the tree trunk, causing decay, disease, and root problems. Unfortunately, volcano mulching kills trees, yet this practice has become so commonplace that many homeowners assume it’s the correct way to mulch.

The concept is fairly simple: trees and shrubs have different parts that serve specific purposes, and each part has adapted to certain conditions. To be specific, the roots of a plant are designed to grow in the soil and soak up moisture. The trunk, in contrast, is designed to grow above ground where conditions are dry.

When mulch is piled against the trunk, the mulch holds too much moisture against the bark, which can cause it to start to break down. As the mulch starts to compost, it heats up, which can further damage the bark and the underlying vascular tissues, compromising the tree’s ability to transport water and nutrients.

The Hidden Damage Most Homeowners Miss

The insidious nature of volcano mulching is that a mountain of mulch, piled high against a tree trunk will not kill it immediately. Rather, it is a slow death, and homeowners don’t associate their actions with tree decline several years after they over-mulched a tree.

Furthermore, a mulch volcano provides an opportunity for the tree’s roots to grow around the trunk. As the roots elongate over the years inside of the mulch volcano, they encircle the trunk. This is called girdling. The girdling action literally strangles the tree and deprives roots and canopy of necessary resources.

Mulch volcanoes bury the roots of a tree and simulate it being planted too deeply. This limits the availability of oxygen and water which can cause stem girdling roots, roots that wrap around the trunk of the tree in search of oxygen and nutrients and inevitably “choke” the tree. Stem girdling roots can lead to dieback, stunted growth, and delayed or shrunken leaves popping out in the spring.

The Five Most Common Mulching Mistakes

1. Applying Too Much Mulch: One of the most prevalent mistakes gardeners make is applying an excessive layer of mulch. While mulch serves many purposes, too much of it can lead to several issues: Water Drainage Problems: Excessive mulch can hinder water penetration, leading to dry soil conditions at the root level.

2. The Dreaded Mulch Volcano: This is known as “volcano mulching,” where mulch is heaped up against the trunk of a tree or plant stem in a cone shape. Unfortunately, this common mulching mistake can cause serious harm to the plant. Mulch that’s piled against a trunk can hold too much moisture, creating an environment ripe for disease and rot.

3. Not Mulching to the Drip Line: The Virginia Cooperative Extension recommends mulching to the drip line of a plant or tree, which ensure the plant or tree will get the most out of the mulch. Mulching to the drip line also minimizes competition from the grass, leading to stronger plants and trees.

4. Failing to Weed First: Weeds should be removed PRIOR to mulching. If they’re not, the mulch can provide the same growing environment for weeds that you’re trying to create for your plants and trees.

5. Using Poor Quality Mulch: All mulches are not created equal. The free stuff can contain pesticides, weed seeds or insects.

The Right Way to Mulch: Professional Techniques That Work

Proper mulching is an art that requires understanding the science behind plant health. The generally recommended mulching depth is 2 to 4 inches, but the key is in the application technique.

Install the mulch around the tree to a depth of 2 to 4 inches. Extend the mulch to the outer edge of the tree’s canopy if possible. Make sure there is no mulch within 4 to 6 inches of the base of the tree. You might be surprised to learn that a mulch ring resembling a “donut” is the proper mulching method for a tree. The tree trunk should be at the center of the tree without any mulch piled up against it.

For different areas of your landscape, the ideal mulch thickness varies by garden area: 2-3 inches for flower beds, 3-4 inches for trees and shrubs, and 1-2 inches for vegetable gardens.

When Professional Help Makes the Difference

For Long Island homeowners dealing with established landscapes, professional tree care can make all the difference. Jones Tree is owned and operated by Thomas Jones – New York State Board Certified Arborist, and member of the Long Island Arborist Association. As a licensed arborist, Jones is committed to providing scientifically based landscape management and delivering quality services. Jones Tree and Plant Care will inspect your landscape, diagnose any problems, and make recommendations based on knowledge and expertise gained through over 10 years of experience in the industry.

Jones Tree and Plant Care tailors specific programs based on the needs of each individual customer and property. A total tree and plant care approach will improve growth, condition and curb appeal of your property, all while using environmentally sensitive, affordable treatments.

Saving Your Investment

Trees are significant investments in your property’s value and environmental health. If you do end up killing a larger, more mature tree, it’s basically irreplaceable in your lifetime. And the cost to remove it could range anywhere from $2,000 to $15,000 or more for one tree.

The good news is that many mulching mistakes can be corrected. If volcano mulching was already performed, and a tree is not severely damaged, in many cases it can be saved. The key is acting quickly and implementing proper mulching techniques before permanent damage occurs.

Don’t let good intentions harm your landscape investment. Understanding proper mulching techniques—and knowing when to call in certified professionals—can save your trees and enhance your property’s beauty for decades to come.