A little bit about mulch from North Carolina State University:
A 2" to 4" layer should prevent most weed seeds from germinating. Mulch should be applied to a weed-free soil surface. Simply covering perennial weeds such as bermudagrass or nutsedge will not prevent their growth. The mulch should cover as much of the root zone as possible.
- Reduces landscape maintenance & keep plants healthy
- Conserves moisture - 10% to 25% reduction in soil moisture loss
- Keeps the soil well aerated by reducing soil compaction
- Reduces water runoff & soil erosion
- Prevents soil & fungi from splashing on the foliage, thus reducing the likelihood of soil-borne diseases
- Helps maintain a more uniform soil temperature (warmer in the winter and cooler in the summer)
- Promotes the growth of soil microorganisms & earth worms
- Provides a barrier between plants & the mower to prevent damage
For beds mulch the entire area. For individual plants, such as trees, the mulched area should extend at least 3 to 6
feet out from the base of the plant. It is advisable to pull the mulch 1 to 2 inches from the base of plants to prevent bark decay.