#620 Mulching for Healthier Plants

A good practice for better landscapes

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Would you like to have healthier plants, better soil and use less water? Regular use of mulches can give you all this and more. What, exactly, is mulch? Mulch is organic or inorganic material that is used as a protective covering placed around plants to prevent evaporation of moisture, insulate roots, and prevent weed growth. It can be coarse or fine and even consist of rocks in some landscapes. “Compost” is mulch that had completed the composting (or decomposition) process. Mulch is for surface applications only, while compost can be used as a mulch or planting mix.


Regular use of mulch also helps drainage and improves the soil. Most mulches release natural humic acids when broken down by soil microbes. These acids neutralize alkali deposits frequently found in our native soils and make nutrients more readily available to plants. Mulch also cools the soil while reducing water use during the hot summer months. Some mulches like bark and rock are highly decorative in the landscape. Others can also be used as amendments to improve soil at planting time. Here are examples of the most common mulches normally used in our area:


Dr. Q’s®Paydirt™ Premium Planting Mix and Mulch is a peat moss based, fully composted product with a small charge of long-lasting organic fertilizer added. It is free of sewer sludge and adds to soil structure, over time, when used as surface mulch. Best when applied as a 1 or 2 inch layer twice a year in spring and fall. Specially formulated for our tough desert soils, Paydirt™ is also the best soil amendment available! Mix it with landscape soil to get all your plants, flowers and vegetables off to the best possible start.


Humus Gro and Top Dressing are fully composted, humus-based products that give a rich color to the soil surface when used as mulch. They also break down naturally when used as surface mulches and release beneficial humic acids. These products can also be used as seed covers and soil amendments. Apply 1 or 2 inch layer in spring and fall to provide maximum benefit to plants.


Bark mulches insulate the soil from heat and cold as well as control evaporation. Coarse, medium and large bark mulches are especially useful in high-wind areas since they aren’t likely to blow around like fine-grained products. Apply a 2 inch layer around plants and in shrub beds. Do not mix bark mulches into soil. They remove nitrogen during the composting process and can cause plant stress if used incorrectly. Scatter fertilizer on top of the bark when feeding your plants. It will speed composting while providing proper plant nutrition.


Bulk or bagged rock is a decorative landscape product that doubles as mulch by reducing evaporation from soil in covered areas around desert shrubs, trees and cactus. Rock is normally applied in 1 to 2 inch layers. Since it is highly heat reflective, be careful when using it around traditional plants. Leave a 2 or 3 foot circle around those plants and use bark or humus-based mulch instead. If using rock over a large surface area, keep in mind that sandstone rock decomposes into soil rather quickly, while quartz rock does not.


Grass clippings and leaves are frequently used as mulches by the home gardener. If using these materials, do not mix them into the soil as they remove nitrogen while undergoing the natural composting process. This can cause severe plant stress. Consider building a composting bin (wire fencing works well). Add the leaves and clippings, sprinkle with high nitrogen fertilizer like Ammonium Sulfate (21-0-0) or a commercial compost starter product. Water and turn the pile over every 2 weeks or so. You’ll have a fully composted mulch in about 6 weeks which will be fine to use around your flowers, trees and shrubs.