Regional Gardening Reports :: National Gardening Association

In the Garden:
Upper South
October, 2010
Regional Report

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Think of autumn leaves as a free way to make your garden better.

Autumn Leaves, Garden Gold

The allure of alchemy, of transforming base metals into gold, has intrigued human beings since ancient Egypt. Although the theory of alchemy may be dismissed by modern science today, it seems to be a natural human inclination to look for ways to turn next-to-nothing into something, whether it's get-rich-quick schemes or dumpster diving. Yet, as gardeners, we often pass up a version of alchemy in our own yards. We stress and strain raking (or even worse, blowing) leaves each autumn and filling landfills, when, with almost no work at all, we could have a wondrous soil amendment and mulch. For free!

This miraculous substance: leaf mold, otherwise known as decomposed leaves. When ready to use in the garden, leaf mold is dark brown to black, has a lovely earthy aroma, and a crumbly texture. Why decomposed leaves are referred to as leaf mold, as they really aren't moldy at all, may be because the decomposition is mainly accomplished by fungi rather than by bacteria as with compost.

Why make leaf mold in addition to compost? While compost is a great soil amendment for improving soil texture and fertility, leaf mold is much better at improving other aspects of your garden soil.

Benefits and Uses of Leaf Mold
Did you deal with drought conditions this year? Want to be able to water less in your garden? Leaf mold can help as it acts as a soil conditioner, increasing the water -holding capacity of soils. University studies have shown that the addition of leaf mold increases water retention in soils by over 50 percent. This same concept make leaf mold a good addition to potting soils as well. In fact, leaf mold (a renewable resource) can be used to replace peat moss (a non-renewable resource) in homemade potting soils.

Leaf mold also improves soil structure. Why care about soil structure? Good soil structure makes it easier for roots to penetrate soil and take up nutrients. Hence, flourishing plants! Plus, leaf mold encourages the soil organisms, like earthworms and beneficial bacteria, that make soil more fertile.

Now think about leaf mold in terms of mulch since it can hold up to 500 times its own weight in water. Placed around, but not touching, your annuals, perennials, vegetables, shrubs, and trees, you can help them maintain even moisture even during the driest of summers. Leaf mold can also be used as a winter mulch to cover bare soil and to protect perennial plants from cold winter temperatures.

Some gardeners even use leaf mold to make their own nutrient-rich seed-starting mix. Simply mix one part leaf mold with one part well-aged compost or worm castings.

Methods of Making Leaf Mold
Basically, leaf mold is simply decomposed leaves. At it's most elementary, you pile up leaves in an obscure corner of your yard and wait at least two years. For those who like neatness and order, make a 3-by-3 foot cage from stakes and chicken wire.

Want to speed up the process to a year, or even six months? Use a leaf shredder or run over the leaves with a lawn mower. Another way to make leaf mold faster is to water and turn the pile occasionally. Or, throw an old tarp (preferably one torn and with holes) over the top. An old piece of carpet will work, too.

Another method of making leaf mold is to fill large plastic garbage bags with either whole or shredded leaves, spray them with water, close the bag, and poke a few holes at the top and bottom for air flow and drainage. Throwing in a shovel of soil or a high-nitrogen fertilizer like blood meal will speed up the decay process.

Two caveats when gathering leaves for making leaf mold: don't use leaves from near roads and highways, as they may be contaminated by vehicle exhausts, and don't collect leaves from woods and forests, where the leaves are already part of a healthy ecosystem. If you don't have enough leaves in your own yard to make leaf mold, then I bet your neighbor's will be glad to give you some of theirs. And don't forget to jump into a big pile of leaves at least once this fall, to celebrate another piece of garden alchemy.

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