In reality, piling mulch around a tree trunk is very bad for the tree and could even kill it. Mulch up against the bark of the tree traps moisture, which can cause the trunk to rot. The bark needs exposure to air, to do its job properly. Instead of protecting the tree, the mulch harbors all types of animal threats, from mice and voles who like the cover of mulch to sneak up on trees for a tasty snack of bark, to pathogens and fungal spores that live in mulch and aid in its decomposition and can’t tell the difference from wood chips and your tree’s bark. There are plenty of insects that use mulch as a conduit to tunneling into your tree. Once the mulch starts the decomposition of the outer bark, it’s even easier for insects to get in.
Mulch is good for a young tree, in moderation. It is a great way to prevent damage from mowing and string trimming and it does help retain moisture and cool the soil, but it should be laid down as a ring, not a volcano. The mulch should extend to the drip line or at least a 2 - 3 radius around the trunk. But it should only be about 2 - 4 inches deep and, very importantly, don’t let it come in contact with the trunk. Mulch is there to serve the tree’s roots, the bark doesn’t need it’s protection. Till next time, Becky Litterer from Becky's Greenhouse, Dougherty Iowa