Mulching is another form of composting. A layer of organic material is added on top of the soil. It mimics what happens on the forest floor where leaves and needles drop to the ground, break down over time and then are taken back up into the plants as food. It is a very slow but efficient way of composting.

Benefits of mulching include:

• water/moisture conservation - mulch acts as a sponge to hold water and nutrients close to the soil, blocking the drying effects of sun and wind to reduce evaporation by more than 70 percent. This encourages healthy plant growth, prevents drying of shallow roots and results in less watering. Mulches also attract earthworms that tunnel through the soil, providing aeration which allows for improved water absorption.
  
• weed control - thick layers can reduce germination and growth of weeds, eliminating the need for herbicides.
  
• insulation - stabilizes soil temperatures, keeping root zones cooler in summer and protects soil from heaving during winter temperature fluctuations (apply after ground has frozen). By covering bare soil, mulch prevents soil compaction and erosion caused by heavy rains and wind.
  soil enrichment - replenishes and enriches the soil as it decomposes, reducing the need for compost, manure and fertilizers. Increased organic matter results in less digging, tilling and cultivation. It improves the soil’s texture: making sandy soil more water retentive and clay soil more porous. It helps to create an ideal environment for earthworms and micro-organisms, essential to healthy soil.
  
• adaptable - may be selected either for its rapid decomposition, its longevity or a combination of both. Most natural or organic mulches gradually break down and decompose to add nutrients to the soil and improve texture and drainage. This is helpful in vegetable plots. In ornamental plantings of flowers, shrubs and trees, you may prefer a more decorative and long-lasting mulch.

Tips on Mulching

• Spread the organic material on top of the soil, around plants and on garden paths. Wood chips, leaves from deciduous trees and shrubs, lawn clippings and sawdust are suitable mulch materials around perennial plants. Around vegetable and annual flower gardens, it is best to use nitrogen-rich (“Greens”) materials like lawn clippings and other green garden trimmings.
  
• Leave grass clippings on the lawn after mowing to add nutrients and reduce water loss.
  
• Annuals, perennials and vegetable seedlings can benefit from a mulch which is moved aside at planting time and then pulled back around the plant as it grows.
  
• Don’t mulch too closely around the trunks of trees (you’ll smother the roots) or too closely at the base of heat-loving vegetables and flowers (mulches cool the soil). Mulch trees out to the drip line, which is the outer perimeter of the tree’s branches.
  
• Mulches can be an ideal hiding place for insects such as slugs and snails. Remove or turn mulch under during the Spring to discourage egg-laying.
  
• Mulch should be no deeper than 5 to 7.5 centimetres (2 - 3 inches) to ensure circulation of air into the soil.
  
• Don’t mulch with weeds containing seeds or persistent roots.

With special thanks to the Greater Vancouver Regional District (604-736-2250) and the City of Toronto (416-392-4689) for use of their informational materials to produce this factsheet.