MASTER GARDENER’S CORNER: Using mulch in the landscape


Anything used to cover the surface of the soil is called mulch. It may be inorganic, like rock or chipped rubber; it may be organic like straw, shredded leaves, chipped wood, or bark.

Why mulch?

Much research has been done over the years to determine the effects of using different types of mulch. The following benefits of organic mulch have been repeatedly confirmed.

Less water is lost from the soil. With the surface covered, less evaporation happens.

Soil temperatures fluctuate less. The soil stays cooler in summer and warmer in winter. This is a healthier environment for root growth.

Weeds are reduced. Excluding light reduces the number of weed seeds that sprout.

Water infiltration increases. Covering the soil prevents the soil from forming a crust.

What type of mulch and how deep?

Many times the type of mulch is a personal choice.

Larger chunks stay put in windy areas and under trees. A 4-inch layer should last three years before needing to be topped off. Be sure to keep mulch 3 to 12 inches away from the base of the plant. The shredded “gorilla-hair” type product weaves together and holds best on slopes. Smaller bark nuggets or chipped wood work nicely in beds with smaller plants. A two- to three-inch layer will provide benefits without smothering plants. Small nuggets will breakdown and need to be topped off every other year.

Don’t forget to mulch large landscape pots and planters.

Though often overlooked, large landscape pots would benefit greatly from the addition of one- to two-inch layer of mulch.

— This article is from North Carolina Cooperative Extension. For more information visit

The Master Gardeners of Colusa County can be contacted by: - Email us at - Call us at 530-458-0570 - Visit us at our plant clinics, farmers markets, Colusa County Fair and at other county events - Visit us at our office, 100 Sunrise Blvd., Ste. E, Colusa, Ca 95932, our office hours are, Tuesdays 9am to 12:00 and 1pm to 4:00