A layer of mulch around your trees helps protect them from mower blades and prevents soil from drying out. But piling it up like a volcano around your tree traps moisture against the trunk, which can cause rot or encourage pests/disease. Additionally, when mulch is too deep, it prevents tree roots from getting the oxygen they need. Always mulch out and not up. Using a hardwood mulch is recommended, which will slowly break down and provide some nutrients to the soil. Just keep your mulch layer to a depth of 2–3 inches.
Reasons for mulching around trees:
- Moisture retention for the tree
- Reduce grass and weeds around the tree trunk
- Helps protect the tree trunk from damage from mowers and weed-wachers
- Provides nutrients and soil conditioning
Proper method of mulching around trees:
Volcanos vs. Donuts?
See a picture of a correct mulch ring below.
No volcanos!
Mulching Guidelines:
Trees should be mulched when planted. The trees should then be mulched when needed. Mulch helps retain moisture in the soil, provides nutrients and soil conditioning, helps to retard weed and grass growth, helps to keep lawn mowers and weed whackers away from the tree trunk to prevent mechanical damage and is more aesthetically pleasing.
Mulching steps:
- Loosen up any existing mulch, if any, if it is crusted over. Crusted over mulch inhibits air transmission to the tree roots and deflects rain water away from the tree.
- Move any existing mulch, if any, away from the tree trunk if deeper than 1”.
- Pull any vegetation that is growing where the new mulch will be placed, if possible.
- Do not spray herbicide on the tree trunk. If herbicide is used, only use minimum amount needed and only use products approved for use around trees and over tree roots.
- Add no more than 3 inches of new mulch for a maximum of 3 inches thick of total mulch (existing and new). The mulch should be about 1” thick at the trunk, taper up to 3” thick, and then taper down to the edge. See the "correct" picture below.
- The mulch should form a ring around the tree, like a donut.
- Any posts or stakes should be incorporated into the mulch ring out to the dripline, if possible.
- The mulch ring should extend out past the root ball (3 to 4 feet in diameter, depending on the size of the tree and where the posts are, if any).
- Excessive mulch against the truck will promote bark rot, pest entry, and cause shallow roots to develop above the root flare.
