Regional Gardening Reports :: National Gardening Association

In the Garden:
Pacific Northwest
October, 2004
Regional Report

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As the weather cools, this maple provides fall's last gasp of color. The leaves will eventually become mulch for my flower bed.

Fall is a Good Time for Mulching

I've heard mulches described as "silent gardeners," and I wholeheartedly agree. Properly applied and maintained, mulched areas prevent loss of water from the soil by evaporation, suppress weeds, moderate soil temperatures, prevent crusting of the soil surface, improve the soil structure, and add beauty to the landscape.

And while I'm contemplating the virtues of mulching, I don't think it is merely a coincidence that leaves fall in the autumn to provide nurturing mulch around plants. Mother Nature has carefully orchestrated this annual event, and I'm taking my gardening cues from her. Mulching, as practiced by gardeners, is merely an adaptation of this natural process.

Advantages of Mulching
Organic mulch never stops working for you. While doing its tasks of keeping moisture in the soil and suppressing the growth of weeds, mulch creates a rich, unified background for plants, shrubs, and trees.

Mulch lowers the soil temperature in summer and keeps temperatures more uniform, favoring beneficial bacterial activity. In the dormant season, winter mulch reduces injury by moderating temperature fluctuations and reducing moisture loss from the leaves.

What Mulch to Use
Any mulch derived from living organisms is termed "organic." Shredded leaves, straw, wood chips, pine bark, and loose pine needles will all break down into humus, improving soil structure and providing nutrients along the way. Inorganic mulches, such as black plastic, will moderate soil temperatures and suppress weeds but will not improve the soil.

How to Apply It
Speedy decomposition is acceptable in a summer mulch, but a winter mulch applied now should be sturdy enough to hold up against the elements and provide season-long protection through winter. I use maple leaves and pine needles because they're so readily available in my garden and because they're slow to decompose. After cleaning debris from the perennial beds and removing any weeds, I apply a 3- to 4-inch layer of organic material over the soil, taking care not to pack it against plant stems or tree trunks. I tuck it around the crowns of low-growing plants, allowing some space for air circulation. Mulch placed too near a crown may hold in excess moisture and cause the crown to rot.

It's Mulch Time
There are two schools of thought as to when to apply mulch. Some insist mulching should be done before the ground freezes, and others insist it should be done after the ground freezes. I'm not sure it matters much, as long as mulch is applied. But it's not a bad idea to follow nature's lead; mulch in the late fall, just before the ground freezes.

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