Sheet Mulching

My least favorite job as a gardener is breaking sod for a new bed. Sure, it’s fun jumping on your digging spade like a pogo stick until it sinks into the soil, but I don’t get a lot of give in my hard clay soils—it kind of gives me a headache. And then there’s the picking up of the sod clumps, shaking off the soil, and throwing the rest on the compost pile. No matter how thorough you try to be, you always miss some sod clumps and have small patches of grass growing in the middle of your bed—I hate that! And if organic gardening is supposed be more true to the natural cycles of the Earth, doesn’t all of that work poking and prodding seem a little contrary? When is nature ever that disruptive and manipulative. There’s got to be a better way!

This spring I tried something new; sheet mulching. When I first heard about sheet mulching it sounded too good to be true. It requires no digging or breaking up of sod, it prevents weeds, and builds up the soil with organic matter, providing nutrients, and attracting earthworms. On top of that, it’s a good way to usefully dispose of newspapers, old phone books, paper bags, cardboard, wood shavings, wood chips, and even carpet and old clothes!

The concept was inspired by the functioning of a forest floor. Stick your hand in the dirt in the forest and you’ll notice it’s much fluffier than the dirt that your grass is growing in. It gets that way from all of the dried leaves and debris that accumulate on the forest floor. And as the leaves and debris decompose, they add organic matter and nutrients to the soil, making it light and fluffy—just like the soil you’d want in your garden. Maybe that’s what the settlers were thinking when they cut down all of the trees. The problem is that when they cut down all the trees, they destroyed their automatic composting system which dropped nutrient-rich, dried organic matter (leaves) on the forest floor every fall. Without that amendment of organic matter every fall the soil lost structure, water retention, and nutrients.

Sheet mulching is a lot like composting except that you accumulate all of the materials at once and spread them on the ground in layers. Just like composting in your compost bin, the layers slowly merge together to form an extremely fertile, nutrient-rich garden bed with great soil structure, making the perfect home for the beneficial insects, worms, and microorganisms necessary for a healthy organic garden.

This is how it works: first mow or cut down all vegetation. This is your first sheet of mulch. Next take a spade or a pitch fork and poke the ground to aerate the area. Now is the perfect opportunity to sprinkle any amendments that you know your soil is lacking. Make sure every layer you put down is wet; this speeds decomposition. Next add a thin layer of a high-nitrogen material like manure, produce scraps, bonemeal or fresh grass clippings. This layer will attract worms and bugs that will aerate the soil. And then comes the most important layer: a weed barrier. That can be newspaper, cardboard, even non-synthetic carpeting or old clothing. Anything that will eventually decompose will work. Don’t use shiny print from newspapers or magazines because the ink contains metal pigments. Make sure there are no gaps in this layer because weeds will find them and grow up through them. Next you can get creative. Look around and use what you have easy access to. Put down a layer of wood shavings, pine needles, manure, food scraps, and/or straw. The more layers, the more active the soil life will be because of the diverse mix of nutrients, but using straw alone will work too. Hay isn’t the best because it has a lot of weed seeds in it. A layer of compost on the top is nice so you can plant seeds into it. However many different layers you have, you want an end product that’s about 8 to 12 inches thick. To plant in your bed just make a hole through the layers and plant right in it. It’s best to sheet mulch in the fall but it does work to sheet mulch in the spring and plant into it after it has settled for at least a couple of weeks.

Everyone tells me, although I have no definitive evidence of my own as of yet, that next spring I’ll be able to dig my spade deep into my garden bed where once compacted life-less, clay soil dwelled. What will have taken its place is the soft, fluffy, nutrient-rich, water-retaining, dynamic and lively soil of a forest floor. It does seem too good to be true– I’ll let you know next spring.

Katie Schmitz

Organic Gardening Specialist

Safe Lawn and Garden Campaign


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