A Living Mulch vs a Traditional Mulch Approach

Adding mulch to a garden is an efficient and easy way to improve your garden's quality and drought tolerance in our dry hot summers with low precipitation. Benefits of mulch include helping to prevent excessive evaporation and dryness by holding and maintaining moisture, keeping the soil underneath cooler for beneficial organisms, and reducing weed growth.

Traditional mulching involves spreading material on the soil surface. This may be straw, shredded leaves, grass clippings, wood shavings, bark chips, garden cloth barriers, plastic or other material. The choice should reflect what you want out of the mulch and how it will affect the soil. For example, with a lighter, finer mulch seedlings can grow through it. Eventually the mulch will break down or can be turned into the soil — desirable in a small or raised vegetable garden. Use as a weed barrier or for moisture retention in landscape areas or between large garden rows may require a heavier or coarser mulch like tree bark chips or wood shavings which can also be laid on top of cardboard or placed directly on top of the soil. Sea shells, stones and rubber mulches do not break down, nor do they add beneficial content to soil.

When spreading mulch material such as straw or wood chips, use a depth of 2-3 inches over the soil but keep a clear perimeter of 4 inches around the base of the plant so that the mulch won't rot or mold at the crown and possibly introduce disease. You may want to compost or fertilize the soil with slow release nutrients per treatment recommendations and water in prior to mulching.

A “living mulch” involves growing “fill in” plants either as a ground cover, cover crop or low growing plants that provide several purposes. A mixture of plants can grow longer depending on seasonal and zone (USDA or Sunset™)appropriate plant choices which can promote the overall health of the soil.

Plants produce sugars through photosynthesis and small amounts of these exude from the roots back into the soil. This process draws and concentrates microbes around the roots providing better access to nutrition for the plant, and can also improve soil structure and ability for rain permeation, deeper root growth, better water holding capacity, nutrient forming capacity and hummus formation, all which contribute to overall healthier long term soil building.

Cover crops that are legumes such as cowpeas or clover build nitrogen in the soil. Thus, these may pair well with vegetables such as corn or brassicas that are heavy feeders and can grow above the lower growing mulch plantings. Taller plants may provide light shade for crop plants such as lettuce. Consider mixing in flowers and taller herbs that bloom, such as dill, as well as cornflowers which will help to draw pollinators. For an edible living mulch seed mix consider using root vegetables such as beets or fast growing golden turnip, a colorful mix like rainbow chard, non-invasive flowers, various green edibles such as rocket, corn salad, purslane, parsley, oregano, creeping thyme and other herbs.

Of course weeds are weeds and you may still have to do some pulling, especially before they go to seed. However there should be much less weeding and you will have a nice variety of plants, edibles, soil builders and color.

You can find out more on several You Tube videos about living mulches if you're interested, but remember to use plants appropriate for the Great Basin and not coastal California for the best success. 

If you have questions about mulch, living or otherwise, please contact our helpline at immg@ucanr.edu.