Avoid building a mulch volcano as shown in the picture.
Tips for placing mulch around a tree:
- Make sure the mulch is at least 5 inches away from the trunk of the tree and no more than 2 to 4 inches deep.
- Spread the mulch around the tree into the surrounding landscape as wide as you like, tapering out to the ground level at the edge of the ring.
- Use fresh natural mulch such as wood chips or bark chips. Mulch can change the pH of the soil, influencing nutrient availability. Pine needles and oak leaves can make the soil more acidic. Plastic mulch will prevent rain or irrigation from reaching the soil.
How does “volcano mulching” harm or kill trees?
- More than 4 inches of mulch depth restricts soil oxygen exchange with the tree and its roots.
- Mulch against the trunk of the tree also creates a moist environment which promotes cracking of the bark, creating an entry point for insects and fungal growth, as well as, favorable conditions for rodents to chew the bark and damage or girdle the tree.
- Mulch around the base of a young tree may promote the roots to grow into the mound of mulch and not into the surrounding soil.
Why put mulch around trees?
Mulch has many benefits:
- Moderates the temperature of the root zone.
- Encourages the conservation of moisture in the soil by reducing surface evaporation.
- Helps control weeds.
- Prevents the soil from crusting over, allowing water to penetrate and percolate.
- Improves soil aeration, soil structure (less soil compaction) and drainage.
- Adds organic matter to the soil, improving fertility.
- Restrains soil erosion, especially raindrop erosion.
- Reduces the chance of mechanical injury to trees and shrubs from lawn mowers and weed trimmers.
- Gives the landscape a more pleasing, manicured appearance.