The Silent Killer in Your Garden: How 'Volcano Mulching' is Choking Our Trees

Picture this: a beautifully mulched tree, seemingly well-cared for. But look closer. Is that mulch piled high against the trunk, resembling a mini-volcano? If so, your well-intentioned gardening efforts might actually be a death sentence for your beloved tree. Horticultural expert Dr. Linda Chalker-Scott of Washington State University Extension calls it a "landscaping epidemic," and it’s silently choking trees across the nation.

The widespread practice known as "volcano mulching" involves piling organic material directly against a tree's trunk.

While mulch is undeniably beneficial when applied correctly, this method creates a detrimental environment. Instead of protecting, it becomes a killer. The mulch acts like a sponge, holding excessive moisture against the bark, leading to a host of problems including root rot, fungal diseases, and a welcoming haven for rodents and insects that chew on the tender bark.

This constant moisture also prevents the tree's essential gas exchange, effectively suffocating it.

Dr. Chalker-Scott emphasizes that trees are designed to have air and light at their base, not a perpetually damp shroud. When mulch is piled high, it encourages roots to grow into the mulch itself, rather than penetrating deep into the soil where they can properly anchor and access water and nutrients.

Furthermore, the base of the trunk, where it meets the soil, is called the root flare. This crucial area needs to be exposed. Burying it under mulch can lead to girdling roots, where roots grow in a circle around the trunk, slowly strangling the tree and cutting off its vital supply lines.

The consequences are dire: premature tree death, diminished health for surviving trees, and wasted investment for homeowners and municipalities.

It's a costly mistake that can be easily avoided with proper technique.

So, what’s the right way to mulch? The answer is simple and effective: think "donut," not "volcano." Apply a uniform layer of organic mulch, such as wood chips or shredded bark, about 2-4 inches deep. Crucially, keep the mulch 6-12 inches away from the tree trunk, creating a visible "donut hole" around the root flare.

This allows for proper air circulation and prevents moisture from accumulating against the bark. The mulched area should ideally extend out to the tree's drip line – the edge of its canopy – mimicking the natural leaf litter found in a forest ecosystem.

When applied correctly, mulch is a tree’s best friend.

It offers a multitude of benefits: it suppresses competing weeds, conserves soil moisture by reducing evaporation, moderates soil temperature (keeping roots cool in summer and warm in winter), prevents soil compaction, and enriches the soil with nutrients as it slowly decomposes. It also provides a protective barrier against damage from lawnmowers and string trimmers, which can easily wound a tree's delicate bark.

Choose your mulch wisely.

Opt for organic mulches like wood chips, shredded bark, or pine needles. Avoid dyed mulches, which can contain questionable chemicals, and steer clear of cypress mulch from unsustainable sources. While inorganic mulches like gravel or rock have their place, they can heat up the soil and are not recommended directly around trees.

By understanding the dangers of volcano mulching and adopting the correct "donut" method, you can transform a silent killer into a powerful protector, ensuring your trees thrive for years to come.

Let's end this landscaping epidemic, one properly mulched tree at a time!