Volcano Mulching, also known as Over Mulching, is the improper mulching technique that piles mulch high around the tree against the tree trunk. This excess mulch can promote surface roots that ultimately end up strangling and killing the tree. Additionally, it can cause too much moisture retention during the wet seasons, promoting fungus, rot, and pests. In the dry seasons, the mulch can completely dry out and repel water, not allowing water to get to the roots of the tree at all. Finally, when mounds of mulch decompose, it becomes a pile of compost and heats up, harming the roots even more.
If you have been Volcano Mulching for years, you may want to consider having Good Nature look at the health of your root system by performing a Root Collar Excavation. See the video below for more information. The pictures below show harmful stem girdling roots and decay due to improper mulching and planting techniques.
If you have smaller trees or trees that have only had Volcano Mulching for a few years, you can probably just excavate the mulch yourself with some garden tools. If you find a lot of surface roots, we recommend contacting a professional.
Trees appreciate mulch around their base so they are not competing with other plants for air and water. Mulch also helps the soil around the tree to stay in place and keeps the soil temperature consistent. It cuts down on weeds and adds nutrients to the soil surrounding the tree as it breaks down. “Donut Mulching” is the best way to mulch around trees. Leave the root flare exposed and pull the mulch a few inches away from the trunk altogether. Small trees can be mulched all the way to the drip line, or their full canopy size, but this is usually unnecessary and unwanted for mature trees, three feet around the tree is a fine maximum. Two to four inches of mulch is a great depth.
As discussed, the application of too much mulch can prove very problematic for the overall health of your trees. We advise that mulch be piled no higher than 3-4 inches off the ground. It's also imperative that mulch be kept away from the base of the tree, creating the appearance of a donut hole around the tree with the surrounding mulch. We recommend keeping mulch roughly 12-18 inches away from the trunk of any tree. Ideally, the mulch around your tree would extend the length of the branches, or at a minimus 4-5 feet in diameter area around the trunk of the tree. The larger the mulched area, the more beneficial.
Mulch should not be replaced or removed, just piled on top of. Mulch will break down and turn into compost, adding nutrients into the soil. We do recommend raking or fluffing up old mulch before applying new mulch on top of it. Raking old mulch will mix it up, making sure it doesn’t harden into a more solid mass and repel water.
Before applying mulch, we recommend removing existing grass or weeds first. Add or adjust your trim or edging to your mulched area to better define the space. And as we mentioned before, rake any old mulch before adding new.
We do not recommend that you use rocks as mulch around trees. While rocks can be a decorative feature, they tend to make their way into your yard and can damage your mower. They do act as a weed block but do not add nutrients to the soil like a plant-based mulch. Rocks can also heat up in the Summer and harm tree roots. We only recommend wood or leaf based mulch such as shredded wood, bark nuggets, or shredded leaves (which last the least amount of time). You also do not want to use pine needles as mulch under any trees that are not pines as it will alter the pH of your soil.
