Mulch to Reduce Evaporation

Mulching is one of the simplest ways to enhance your garden. Mulch insulates the soil, protects it from erosion, conserves moisture, reduces weed growth, reduces soil compaction from heavy rain, provides a beautiful finishing touch to your garden, and may even improve soil quality.

Mulching, or top dress, refers to covering the bare ground in your garden by spreading an organic material, or some sort of rock. Many materials have been tried and proven effective as mulches: compost, manure from poultry and herbivores, including chickens, horses, and goats, ground bark, leaves, sawdust, straw, processed by-products (grape and apple pumice), lawn clippings, and old newspapers.

Most medium and high water-use plants will benefit from a two-inch protective layer of organic mulch on the soil surface above the root area. Mulch will moderate soil temperature (keep soil cool), reduce water evaporation between watering, and reduce undesirable weeds. For plants that live in dry climates, substitute crushed rock as a cover for bare ground. It also reduces evaporation and weeds.

•	Purchase organic mulches that are guaranteed weed-free. Straw, hay, and many types of manure, for instance, may contain weed seeds.

•	To protect plants from insects and rot, which thrive in moist conditions, keep organic mulches a few inches back from the crowns and trunks of woody plants.

•	On steep slopes where terracing is not practical, mulch areas with coarse-grade bark, which is heavy enough not to be easily blown or washed off by rain.

•	Under existing oak trees, use a stone mulch to cover the bare soil and do not plant anything, leaving the stone mulch itself as a ground cover.

•

Sheet mulching is the process of covering the soil with a layer of cardboard and/or newspaper and mulch to kill stubborn weeds. It works better than herbicides and at a much lower cost to the environment. Cover the soil with one to three layers of corrugated cardboard or 4-6 sheets of newspaper. The cardboard and newspaper decompose in place, adding valuable organic matter to the soil. When you are ready to plant, make a slit or cut an “X” through the cardboard or newspaper and plant as usual. Keep mulch six inches away from the trunks of trees and shrubs. Contact between mulch and trunks can harbor pathogens and possibly harm the plants.

•

Newspaper - Use only black and white text pages. Cover the soil with newspapers 4-6 sheets thick, layer with clippings and manure (turkey manure works well) to keep the papers from blowing away. Wet down with a hose and cover with chipped bark. This method is especially good for weed control; newspapers do not contain weed seeds. If you want to plant within the area of the newspaper mulch, cut an “X” through the newspaper, fold it back, loosen the soil with a trowel, and plant. Fold the newspaper back, making sure the mulch is clear of the plant’s stem to avoid rot.

Myth No. 1: Mulch provides a permanent barrier to weeds. While mulch reduces the number of weeds, some pesky nuisances may still manage to grow through the mulch, or on top of it. Weeds are especially likely in a new landscape for the first year or two, even with mulch, because of the abundance of weed seeds in the soil. However, once the weeds are brought under control, fewer will follow. Organic mulch needs to be replenished when decomposed to less than 1 inch thick.

Myth No. 2: Mulch placed against your house will attract termites. In reality, it’s moisture, not mulch, which attracts termites. So any landscaping, including shrubs, can lure the unwanted critters. Irrigation systems up against the house also create a termite-conducive environment. Even gravel or rocks around the base of a house can hold in the moisture attractive to termites.

Myth No. 3: There’s no wrong way to mulch. When mulching, keep the bark or rock one to two inches away from stems. Mulch creates a warm and humid environment that is perfect for the establishment of various fungi that can injure or kill the plants. Also, avoid covering the crown of dormant perennials.