Mulching
Mulching involves spreading a protective layer of material, called mulch, over the soil’s surface. Mulch may be either organic material, such as wood chips or leaves, or inorganic material, such as rocks.
Benefits of Mulch
Done properly, mulching is a simple and effective way to promote tree health. It has many benefits, including:
- Reducing moisture loss due to evaporation
- Insulating the soil against extreme heat and cold
- Choking out weeds
- Improving soil fertility as the organic matter in the mulch decomposes, releasing nutrients
- Protecting against “mower blight”—wounds caused by mowers or weed whackers that may lead to decay
- Beautifying your landscape—many homeowners prefer the tidy appearance of mulched beds
How to Apply Mulch
Winter is a great time to mulch before the extreme heat and drought of summer sets in.
Apply a moderate layer of mulch, 2–4 inches thick, over as much of the root zone as possible. At minimum, the mulch layer should cover a 3–5 foot radius around, but not touching, the trunk. A 10 foot radius is ideal.
If possible, use organic mulch for its beneficial impact on soil fertility as it decomposes.
Mulching Mistakes
The main goal when mulching is to cover the radius of the root zone without covering the trunk. “Mulch volcanoes,” excessive piles of mulch which form a cone around the base of the trunk, are the worst example of this problem.
Applying mulch against the trunk may soften the tissue and exacerbate insect and disease concerns. It may also lead to stem girdling roots which compress the stem and degrade the tree’s ability to take up water and nutrients from the soil.
Avoid overmulching. Layers of fine mulch that are too thick may become matted and prevent air and water from penetrating into the soil.
Avoid dyed mulch. The chemical dyes may leach into the soil as the mulch decomposes.
