Although using mulch has many benefits, it cal also be detrimental to the garden in mainly two ways:
- Overmulching can bury and suffocate plants
- Mulch provides a convenient hiding place for pests
- Bake your plants with excess heat if don incorrectly
With most organic mulches, a layer of 2 to 4 inches is plenty. The finer the material, the thinner the layer needed.
Unfortunately, mulch provides the perfect place for slugs, snails, and other pests to hide. Use shallow cups of beer to attract and drown them, or sprinkle wood ashes or diatomaceous earth around the base of precious plants to keep the slugs and snails at bay.
Impervious mulches, like black plastic, don’t let air or water in. Even matted leaves can have that same effect, so shred or chop them up first.
Light-colored, wood-based mulches, like sawdust or fresh woodchips, can steal nitrogen from the soil as they break down. Counter this effect by adding a nitrogen-rich fertilizer, such as soybean meal, alfalfa, or cottonseed meal, to the mulch.