Bark provides an attractive type of mulch with good longevity, but if bark is not partially decomposed it may cause a nitrogen deficiency. Some species of trees, such as hardwoods, have bark that decomposes much slower than other species. Bark is relatively inexpensive and can be purchased in bags or by the yard from most garden centres or landscape supply companies. Bark is effective in reducing compaction and is not easily blown by the wind.
Pine needles are attractive, resist compaction, and decompose slowly. They are not readily available for purchase; however, they can be taken from beneath pines found on your own property at no cost. Pine needles will acidify the soil in time (this is a long process if the soil in your area is naturally alkaline).
Both fine and coarse textured wood chips can be purchased, though fine textured mulches decompose at a greater rate and more frequent applications will be required. Coarse textured mulches may be considered less aesthetically pleasing. Wood chips can be obtained from municipalities for little or no cost. You may also need to provide additional nitrogen to prevent depletion in the soil.
Leaves have a pleasing appearance and can be shredded with a composting mower or lawn mower and added to the garden. Shredded leaves decompose quickly, however, and must be replenished regularly. While leaves are available at no cost, theymay cause a nitrogen deficiency. Whole leaves should not be added as they tend to mat and block water from infiltrating the soil. Well-rotted leaf mulch is perhaps the best mulch, providing nutrients as it breaks down into beneficial humus.
Straw has a coarse appearance that may be undesirable for some and will require frequent applications. Straw is inexpensive mulch that is ideal in vegetable gardens: while it provides the benefits of other mulches, it also keeps the fruits and vegetables clean. Note that nitrogen should be added to prevent depletion of this nutrient and that straw may carry weed seeds.