Spreading mulch around trees doesn’t just serve an aesthetic purpose; it helps the tree to absorb water and nutrients as well. If you don’t mulch your trees correctly, however, it can actually do more harm than good. The most common mulching mistake is the practice of building mulch up around a tree trunk, rather than spreading it out and away from the tree.
You’ve probably trees like this before, where mulch around the base of the trunk rises up in the shape of a volcano. This cone of mulch might look nice, but it can have a number of negative effects on the health of the tree.
To begin with, a dense pile of mulch can effectively suffocate root systems by causing soil to become waterlogged and oxygen-deficient. All that excess moisture buildup in the mulch can also cause the living tissue in the inner bark of the tree trunk to rot and die. Finally, a wet, dense pile of mulch can promote harmful fungal growth and invite insects that feast on wood. You may not notice the effects of over-mulching right away, but over time it will compromise the health of a tree and potentially cause it to die.
Instead of mulching in a tall cone shape, a much better option is to mulch in a low, wide, doughnut shape. Spread the mulch out away from the trunk and create a low ring that’s no more than 2-4 inches high. This bowl shape will allow the tree’s root system to breathe while allowing moisture to soak gradually and evenly into the soil. The thin layer of mulch will also decompose over time, replenishing the soil with fresh nutrients.
Just remember: mulch out, not up. Your trees will thank you!