Gardening: Don’t toss leaves – they are free fertilizer

Nancy Szerlag
Special to The Detroit News
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Autumn leaves are Mother Nature’s way of returning nutrients to the soil that trees, flowers and shrubs extract throughout the growing season. That’s what she used to grow the giant redwoods in California. Sadly, too many homeowners collect this free fertilizer and take it to curb side marked as yard waste.

When shredded, leaves make great mulch for the garden, but you can also turn them into leaf mold, which makes a great soil amendment for the garden that’s biologically active and has natural moisture holding capacity as well as nutrients

Don’t freak out over the word mold. Leaf mold is nothing more than composted leaves and it has no nasty odors – just a rich earthy smell, like the forest floor. And the best news is it doesn’t attract animals or contain weed seeds.

If you let Mother Nature do her thing it may take a year or more for leaf mold to develop from a pile of leaves. However, you can help things along by shredding the leaves with a lawn mower or a leaf vac. Shredded leaves decompose more quickly and they don’t fly around like whole leaves that become airborne like tiny kites when the wind blows.

To speed up the process even more, mix in a nitrogen source as you build your pile. Grass clippings, leftover organic fertilizer, composted chicken manure or a combination of any of the above works. I also toss in coffee grounds. If you can find grass clippings, mix them up to half and half with the leaves. When using organic fertilizers to accelerate decomposition, pile up 6 inches of the shredded leaves and water down the material so it’s moist but not sodden. Then scatter a quarter of a cup of the organic granules on the surface of the pile, and continue building.

All is not lost if leaf piles are verboten where you live. Forty-gallon black plastic bags with holes punched in them also work and you can store them in the garage. Rolling them around every few weeks helps speed up the process and your leaf mold should be ready in 9 months to a year.

Even partially decomposed leaves make great garden mulch. If you’re short on time and space, mix freshly shredded leaves in with the top 2 or 3 inches of garden soil this fall to enrich the soil.

When your leaf mold is “done,” sift it through a hardware cloth screen and use the fine particles to make a premium moisture holding, biologically active additive for potting soil.

Did I mention it’s free?

Nancy Szerlag is a master gardener and Metro Detroit freelance writer. Her column appears Fridays in Homestyle. To ask her a question go to and click on Ask Nancy. You can also read her previous columns at /homestyle.

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