FALL MULCHING

Enlarge Image Image Gallery Sandy Langhorst, of Santa Rosa, California, prepares her autumn garden with a dried-leaf mulch. PHOTOGRAPH ? DAVID CAVAGNARO

SEASONS OF THE GARDEN

The why's, what's, and how's of taking cover this autumn

By Stu Campbell

FALL MULCHING HAS MANY BENEFITS not the least of which, as far as I'm concerned, is that you can walk around in your garden on rainy days and not have three inches of sticky mud on the soles of your shoes when you come back inside.

But besides acting as organic StainMaster, laying mulch in the fall (and mulching anytime, really) reduces water loss in soil, suppresses weed growth, and protects plants from temperature extremes—the final warm October days and first wintry November nights.

Soil Moisture Retention

Mulch's ability to conserve soil moisture has long been documented. It may be its most universally recognized virtue. While authorities and test results differ, it is clear that moisture evaporation from soil covered with mulch is reduced anywhere from 10 to 50%. Whichever you accept, the water-conserving value of mulching can't be overemphasized, especially in these times of water restrictions and shortages.

Mulch keeps the soil from drying out partly because it prevents dew and water drawn up from the subsoil from escaping. Contrary to what a lot of people believe, dew is not simply condensation of water from the atmosphere. It is also condensation of moisture from the air pockets found in the soil. Most dew is completely wasted, as far as plant growth is concerned, unless there is something on the surface to catch it and prevent it from evaporating.

Weed Suppression

As for weed control, one study has found weeding time to be reduced by almost two-thirds through the use of mulches. Proper mulching can practically eliminate the need for weeding and cultivating.

There are a few catches, however. First, the mulch itself must be weed-free. Many a gardener has had the best mulching intentions go astray with one application of weed-strewn hay or manure. They end up introducing more weeds to their garden than they controlled.

Second, a mulch must be deep enough to prevent existing weed seeds from germinating. As with most other seeds, weeds need light to germinate. Those weeds trying to come up under a mulch sprout in darkness and wither away. If a mulch is apold too thinly or unevenly, weeds may still find their way through. So when applying your mulch, you'll want to think like a weed and cover all the open areas.