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Still, Dr. Brinton explains, chemical contamination is not a significant concern with leaf mold because its lengthy decomposition time allows for chemicals to break down as well. Do not use leaves that have been raked into the street for municipal pickup, because they may contain lots of sand, fuel, or oil residues.
What Is Leaf Mold?
Leaves that have fully decomposed over a long time.
Compost made by mixing leaves with other organic materials.
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The dark, spongy material created when microorganisms break down organic matter. Leaf mold and leaf compost both eventually turn into humus.
Do-It-Yourself Leaf Mold
Making leaf mold couldn't be easier. Start by ensuring that the leaves are thoroughly moistened, says Abigail Maynard, Ph.D., of the Connecticut Agriculture Experiment Station. Dehydrated leaves begin to lose nitrogen, and this hinders the decomposition process. Here are two ways to transform leaves into leaf mold.
The Lazy Gardener
Pile leaves in a sheltered, inconspicuous area of your yard and leave them for two years.
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The Ambitious Gardener
Make a 3-by-3-foot leaf mold "cage" from stakes and chicken wire. Speed up the leaves' rate of decomposition by running a lawn mower over the pile a few times. To ensure even decomposition, Dr. Maynard suggests, turn the pile occasionally.
How To Use Leaf Mold
Now, here's how to use this nutrient-rich soil conditioner.
Use leaf mold in place of peat because it has similar qualities and it's a renewable resource.
Leaf mold can hold up to 500 times its own weight in water. Place it around (but not touching) the crowns of annuals, perennials, and vegetables to help them maintain moisture during summer.
It's easier for roots to penetrate soil and take up nutrients when the soil is not as dense. Dr. Maynard and her colleagues in Connecticut completed a 12-year study on the role leaf mold plays in changing soil characteristics. They found that garden soil amended with leaf mold had a 20 percent lower bulk density than soil to which leaf mold was not added.
The Connecticut study also found that soils amended with leaf mold increased their water-holding capacity by almost 50 percent. The amended soil could hold nearly a two-week supply of water for vegetables. Caution: This water-holding capacity can be a problem for seeds planted in early spring, because they may rot in the cool, wet soil. Dr. Maynard suggests planting extra seeds to compensate for seeds lost to rot.
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Mix one part leaf mold with one part well-aged compost or worm castings for a nutrient-rich potting mixture for seedlings.