Mulch could be a gardener’s most effective secret weapon, especially in the fall.

Stu Campbell, author of The Mulch Book: A Complete Guide for Gardeners, explains that adding mulch to your gardens in cooler months not only reduces water loss in soil and suppresses weed growth, it also protects plants from temperature extremes.

If you think of mulch as insulation, then you can understand how it can keep underground soil and plant roots cool or warm during fall’s rapid the temperature shifts.

Typically, plants that need mulch protection are rhododendrons, azaleas, roses, bulbs and annuals.

Depending on the plant, several types of mulch can be applied. For rhododendrons and azaleas, an organic mulch like leaves or pine needles may be appropriate. Weathered wood chips and sawdust or peat moss can be substituted for pine needles. Other appropriate materials are corncobs, nut shells, grape clippings, rotted manure and compost.

Campbell says to mulch annual beds early before the first frost has settled into the soil, “so that earthworms and beneficial microorganisms can stay at work longer during the cold months.”

Volunteer for Maple Valley Make A Difference Day, Saturday, Oct. 26.

Visit LakeWildernessArboretum.org, email info@lakewildernessarboretum.org or call 253-293-5103 to volunteer or donate.