Fresh mulch makes a landscape look tidy, and when applied well it protects trees. Applied poorly, it can shorten a tree’s life. Extension horticulturists describe the most common mistake as a mulch volcano, a cone of mulch piled against the trunk.
What good mulch does
Mulch holds soil moisture, moderates soil temperature, reduces compaction and suppresses weeds that compete with the tree. A ring of mulch also keeps lawn equipment well away from the trunk and roots.
Why volcanoes cause harm
Mulch piled against bark traps moisture and encourages decay, giving insects and diseases a way in. It can bury the root flare, the spot where the trunk widens into the roots, which needs to stay visible so roots can get oxygen. Deep piles can also trigger roots that grow from the trunk and eventually girdle the tree, and they give rodents such as voles cover for chewing on bark.
Think donut
- Spread mulch in a wide, even ring that reaches out toward the edge of the canopy, the drip zone.
- Keep it clear of the trunk. Recommendations range from at least 3 inches to 6 inches of open space.
- Apply 2 to 4 inches deep. Use a thinner layer, about 2 to 3 inches, on heavy soils that drain slowly.
- For a tree in a lawn, a mulch ring about 3 feet across for each inch of trunk diameter is a common guideline.
Mulch should be reapplied each year so the layer stays at the right depth.
Timing
Spring is a good time to add a ring, but it can be done at any time of year. When creating a new ring in turf, remove the sod carefully so you do not damage roots.
Filed under: Washington DC Home & Garden News
