For growing vegetables and fruit, black plastic and straw are the most commonly used forms of mulch, while shrub beds and trees thrive on wood chips, bark chunks and pine needles. Annual and perennial beds are attractive with fine mulches such as cocoa shells, buckwheat hulls and bark granules, while gravel and crushed stone look best in rock gardens.
Black plastic mulch is good at warming the soil in the spring, but it can also cause the soil to heat up too much in the summer. For those who want to control soil moisture, black plastic mulch prevents evaporation from the soil. However, it also prevents moisture from entering the soil. Organic materials, such as pine needles, leaves and bark, insulate well in the winter but are slow to warm the soil in the spring. Synthetic mulch adds no new nutrients to the soil, but it is sometimes able to help prevent the growth of weeds and spread of disease.
Plants that are highly acidic, such as blueberries, rhododendrons and other evergreens, do well with sawdust or pine needles as a mulch. While straw is a good insulating mulch for the winter, it is highly flammable and can attract rodents.