Lasagna gardening is a no-dig, no-spray way to start a garden
- Perhaps you should plant to try one this spring.
The first time someone called my office to ask about lasagna gardens, I was certain that they were trying to pull a fast one on me. I’d seen all the April Fools articles about marshmallow bushes and spaghetti trees, and I thought this was another gag. Turns out, though, this is a seriously neat way to start a new garden area without needing to dig up the existing sod or spraying herbicides to kill it.
Lasagna gardening is also known as “sheet composting,” “sheet mulching,” or “no-dig garden beds.” This uncomplicated and easy gardening method is appropriate for everyone (including people who may be physically limited or unable to dig traditional garden beds). It’s also a good way to convert grassy areas to gardens without using herbicides or tillers. The sod is left in place, where it gets converted into soil organic matter. The process can be done at any time and at any scale, even piecemeal as materials are available.
There are several benefits of lasagna gardening over composting. First, you don’t need to buy or build bins, although some gardeners do use lumber or bricks to make a short raised bed and prevent the layers from spilling out. Also, there is no turning or aerating of the pile needed. Earthworms will work their way up through the wet cardboard and materials, and will aerate the bed for you.
Lasagna gardens, over time, create a high-quality soil without any of the drawbacks of tilling the garden. Tilling the soil can bring weed seeds to the surface, increasing your weed problems. If you are gardening on a slope, soil erosion is a concern. Over-tilling (often done with mini-tillers between the rows as a weed-control chore) can break down soil structure, and affect the levels of beneficial bacteria, fungi and earthworms.
Where and When to Start
Lasagna gardens are normally built several months before it’s time to plant to give the materials time to decompose. However, for those of you who want to build one and plant this spring, I’ll include a tip to do that successfully toward the end of this article.
Start by planning where you want to place this garden. A lasagna garden is not the most attractive thing you’ll see in your landscape, so most gardeners tend to hide these in corners. Be sure, however, that the site is conducive to whatever you’re growing (full sun for vegetables for example). Avoid installing the bed over tree roots, septic fields or other utilities.
The bed should be no wider than 4 feet. This way, you can reach the center from either side for planting or harvesting. The lasagna garden will be extremely loose and fluffy, and any walking on it will compress the material and decrease its usefulness.
The first layer of the lasagna garden should be corrugated cardboard. Large boxes from refrigerators or other appliances are ideal, but even smaller pieces can be used if they are overlapped. This layer blocks light from reaching the soil, preventing weed seedlings from penetrating. It also serves as a carbon source. If you can’t get cardboard, use six to 10 sheets of newspaper, being sure to overlap the edges by 4 to 6 inches.
The cardboard needs to be moistened before laying it down; however, hosing down a sheet of cardboard rarely works well, as the water just runs off. Experienced gardeners tell me that filling a barrel or even a wheelbarrow with water and letting the cardboard soak in there will allow the water to penetrate.
Next, place a layer of nitrogen-rich “green” yard waste, like grass clippings or fresh vegetable peelings. Compost or rotted manure can also be used. On top of this add a layer of carbon-rich “brown” material, such as dry leaves, sawdust, or straw; you can even use shredded paper, if you have access to large amounts of it. Each layer should be about 3 to 4 inches thick. Continue alternating layers until the bed is as tall as you desire (usually between 18 and 36 inches thick). Be sure to moisten down each layer with your garden hose to encourage decomposition.
When the bed is as high as you want, cover it with burlap, bark chips or sheets of plastic. This will keep the heat in, allowing decomposition to work faster. It also helps prevent the ingredients from blowing around the yard. Even with the covering, lasagna gardening is considered a “cold” decomposition process. The seed-killing temperatures we seek in compost piles (130 to 160 F) won’t be reached in sheet composting. This means you need to be extra careful not to include weeds that have gone to seed when adding to your green layers.
Another item to avoid is any meat scraps, bones, grease or other animal products. As with standard compost piles, these materials draw rats and other vermin, and can become rancid and produce foul odors.
Normally, it would take about six months for this material to decompose well enough to plant in. For gardeners who wish to plant into the lasagna garden immediately, they can add a 2- to 3-inch layer of topsoil mixed with compost as the uppermost layer. Again, since we’re not going to build up high temperatures as we would with a larger compost pile, there should be little risk to young seedlings.
Plant It Up
To plant into the bed, make a planting hole by pulling the layers apart with your hands. Set the plant in the hole, pull the materials back around the roots, and water thoroughly. If you want to plant seeds, spread fine compost or damp peat moss where the seeds are to go. Set the seeds on the surface and sift more fine material to cover them.
Over the course of the gardening season, the bed will shrink in height as the various materials decompose. This is expected, and is not a big problem. In the fall, rebuild the bed with alternating layers of “greens” and “browns,” and let it decompose over the winter. Be aware, though, that as the various layers break down, there will be temporary deficiencies of mineral nutrients, so be prepared to side-dress your crops with garden fertilizer several times during the season.
Many gardeners will stockpile the raw “ingredients” of their lasagna garden during the off-season, so they don’t have to scramble for it when they’re ready to build the next section. Cardboard can be unfolded and stored flat in a garage or shed. Newspaper can be stacked and tied into neat, easily handled bundles. Dried leaves can be shredded with a lawnmower and stored in yard bags. During the winter, vegetable peelings and other kitchen scraps can be stored in airtight containers outside where it can freeze, but not be accessible to raccoons, rats and other vermin.
I hope you try lasagna gardening this year. Drop us a line and tell us how it worked!
A version of this article appeared in print in Indiana Gardening Volume VI Issue 2.
Photography by Patrick Byers.