| (Find out more at a Water Efficient Landscapes Workshop)
Mulching is one of the most beneficial landscape practices. Mulches conserve moisture by preventing evaporative water loss from the soil surface and reducing the need for supplemental irrigation during periods of limited rainfall. By maintaining an even moisture supply in the soil, mulches prevent fluctuations in soil moisture that can damage roots. Mulches also prevent crusting of the soil surface and allow water to penetrate readily to plant roots. They insulate the roots of plants from summer heat and winter cold and help control weeds that compete with plants for moisture. By serving as a barrier between the plant and soil, mulches help discourage soilborne diseases that stress plants and cause them to have a higher demand for water.
Islands of unplanted organic mulch designed to blend with the landscape are an economical way to retrofit an existing landscape to make it more water efficient while reducing maintenance requirements. Aside from occasional weed control and topdressing with additional mulch, unplanted mulched areas require no water and little routine maintenance.
Pine straw, pine-bark, mini-nuggets and shredded hardwood mulch or chips are some of the best mulches for a water-wise landscape. These fine-textured mulches hold moisture in the soil better than coarse-textured mulches like large-nugget pine bark. They also are nonmatting and allow water, nutrients and oxygen to freely penetrate to plant roots. Inorganic mulches, on the other hand, such as rock, gravel and marble, absorb and reradiate heat from the sun and increase water loss from plants and soil.
Apply approximately 3 inches of mulch under ornamental plants in the landscape. Avoid applying too much mulch because it encourages shallow roots, which are easily damaged by excessive cold, heat or drought.
Where possible, extend the mulched area two to three times the canopy spread of ornamental trees and shrubs. Research shows that the roots of ornamental plants grow far beyond the canopy spread, so mulching as large an area as practical is important. Once mulch is in place, use your hand to pull it back 2 to 3 inches away from the trunk of trees and shrubs. Keeping mulch away from the trunk will help prevent wood rotting diseases. During periods of limited rainfall, make certain sufficient mulch is maintained beneath plants. If watering restrictions prevent you from irrigating, mulches will help conserve the moisture remaining in the soil.
Placing newspapers under organic mulches not only improves water conservation in the soil but also is an excellent way to recycle. Place them on the soil surface under organic mulch at planting time. They may also be used on established ornamentals by carefully removing the organic mulch from around the plants, placing the newspapers two sheets thick on the soil surface and reapplying the mulch. Be sure to wet the newspapers thoroughly immediately after application; otherwise, they may pull moisture from the soil.
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