Mulch in the Garden

February 26, 2005

By Suzzanna Walsh, Master Gardener

Let‘s cover the subject of mulch. How can I make mulch sound like a fun subject? How about this? Does less watering sound like fun? Does less weeding sound like fun? Does more sitting, sipping ice tea, and enjoying your garden sound like fun? Maybe I’ve succeeded in making mulch a fun subject.

So, exactly what is mulch? The University of California Master Gardener Handbook tells us mulch is “Any materials placed on the soil to conserve soil moisture, moderate soil temperature, prevent soil erosion, or prevent weed growth."

This simple definition explains a lot. Use mulch for all these purposes. Let’s look at each purpose.

1. To conserve soil moisture - This allows the soil to soak up and retain more water. Apply 2 to 6 inches (depending on the material), or use a landscape fabric underlay.

2. To moderate soil temperature - Mulch reduces fluctuations in soil temperature that could be harmful to plant roots - especially young ones.

3. Mulch helps to prevent soil erosion by lessening the impact of rain on soil surface.

4. Mulch helps to prevent weed growth. For this purpose apply mulch 1 - 3 inches deep.

Apply mulch in late spring. Do not lay mulch next to tree trunks to avoid crown rot and other potential problems. There are organic and inorganic mulches. Here is a sampling of organic mulches: bark, wood chips, sawdust, straw, pine straw, and shredded leaves; and inorganic mulches: crushed stone, gravel, volcanic rock, and plastics.

When deciding how much mulch, or what type of mulch to use, think tender or hardy. For tender, shallow-rooted plants like vegetables or annuals apply light mulch thinly. For hardier plants like shrubs, apply mulch thicker using chipped or shredded wood. Also bear in mind that using an undecomposed mulch can temporarily tie up nutrients at the soil surface.

Mulches look attractive in your landscape, and are beneficial to your plants, soil, spinal health and free time. Do yourself, your yard, and your environment a favor: do some winter planning and then some springtime mulching.

University of California Cooperative Extension Master Gardener Volunteers can provide additional gardening information upon request .Call the San Luis Obispo office at 781-5939 on Mondays and Thursdays from 1 to 5 PM. You may also call the Paso Robles office at 237-3100 on Wednesdays from 9 AM to 12 PM. The San Luis Obispo Master Gardeners website is at http://groups.ucanr.org/slomg/. Questions can be e-mailed to: mgsanluisobispo@ucdavis.edu.