Benefits of Proper Mulching

  • Helps maintain soil moisture. Evaporation is reduced, and the need for watering can be minimized.
  • Helps control weeds. A 2- to 4-inch layer of mulch will reduce the germination and growth of weeds.
  • Mulch serves as nature’s insulating blanket. Mulch keeps soils warmer in the winter and cooler in the summer.
  • Many types of mulch can improve soil aeration, structure (aggregation of soil particles), and drainage over time.
  • Some mulches can improve soil fertility.
  • A layer of mulch can inhibit certain plant diseases.
  • Mulching around trees helps facilitate maintenance and can reduce the likelihood of damage from “weed whackers” or the dreaded “lawn mower blight.”
  • Mulch can give planting beds a uniform, well-cared-for look.

Trees growing in a natural forest environment have their roots anchored in a rich, well-aerated soil full of essential nutrients. The soil is blanketed by leaves and organic materials that replenish nutrients and provide an optimal environment for root growth and mineral uptake. Urban landscapes, however, are typically a much harsher environment with poor soils, little organic matter, and large fluctuations in temperature and moisture. Applying a 2- to 4-inch layer of organic mulch can mimic a more natural environment and improve plant health.

The root system of a tree is not a mirror image of the top. The roots of most trees can extend out a significant distance from the tree trunk. Although the guideline for many maintenance practices is the drip line—the outermost extension of the canopy—the roots can grow many times that distance. In addition, most of the fine, absorbing roots are located within inches of the soil surface. These roots, which are essential for taking up water and minerals, require oxygen to survive. A thin layer of mulch, applied as broadly as practical, can improve the soil structure, oxygen levels, temperature, and moisture availability where these roots grow.