by Erin LaFaive, UW Extension
Lasagna gardening is a method of gardening somewhere in-between creating a raised bed and composting. This type of gardening is also known as sheet composting, sheet mulching, and no-dig.
There are many benefits to this type of gardening: • Use up existing materials. • Less weeding and watering requirements. • No tilling necessary. • Great garden method for poor soils.
In general, lasagna gardening is similar to cold composting. Cold composting doesn’t require much attention except adding organic material and some moisture, and time to break down. In contrast, hot composting requires regular turning of the materials and monitoring of temperature to get the organic material to break down at a faster rate.
Rather than tilling the ground to create a conventional in-ground garden, lasagna gardening is created on top of the soil surface. Because of this there are less weeds. Starting a garden in an existing lawn or garden has a seed bank waiting for optimum condition to grow. Even if you take out a foot of soil from the ground and replace it with something else, seeds are still alive in the soil below and may get rotated in through tilling. Some weed seeds could be in the materials used during lasagna gardening; however, the amount is greatly reduced. Each year organic materials are added to maintain the height of the garden, thus weed seeds are smothered by organic material and are unable to get sunlight, which they need to grow.
Since the garden is high in organic material, it retains moisture well, and less watering is needed. The only soil (sand, silt, and clay) that’s added to the garden is added by you. Using the organic materials around you is not only frugal, it’s environmentally friendly. Some lasagna gardeners do purchase materials if they are low on organic materials. If you’re in this situation, consider swapping materials with someone. If you have a surplus of one material, perhaps you can trade with someone who has too much of another organic material. In many cases, people are more than willing to give away leaves. Be certain there aren’t any black walnut trees in their yard. Those leaves have toxins that can stunt or kill certain plants.
The best time to start a lasagna garden is in fall; the next best time is spring; and the least desirable is in summer. Fall is the best time to start the garden because during the winter and early spring, the pile of organic material has time to break down. The spring time allows for some breakdown, and the summer is so hot that the materials may produce an odor from breaking down quickly.
Step by Step
1. Gather at least three different types of organic material.
2. Lay down the first layer using cardboard, newspaper, or wood chips. When using cardboard, overlap seams 3-4 inches to keep creeping weeds out and remove any packaging tape. When using newspaper, use 6-10 sheets thick. Wood chips should be at least 3 inches thick and slightly composted.
3. Start layering materials until the bed is 18-24 inches deep. As it breaks down, it will compress to about 6-12 inches.
4. Put transplants in the garden by moving away the organic material to produce a hole, set the plant in, and move the material back around the roots.
5. To plant seeds, make a shallow trench and add some soil. Seeds need good seed to soil contact in order to germinate. As they grow, the plant will take root in the organic material.
6. Water thoroughly.
7. Each fall, add more organic layers to keep the garden about 6-12 inches (after it compresses).
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Use more browns than greens. A general rule of thumb is to use the ratio 3 part brown to 1 part green material.
Some compostable materials requiring special handling
• Cardboard is slow to break down. It’s best to use only for the first layer close to the turf. Because of the slow break down time, it smothers turf and weeds effectively. • Corn cobs are also slow to decompose; therefore, shred or chop into small pieces and make sure to add a nitrogen source. • Some diseases overwinter on plant debris. Put diseased plants (such as tomato plants with blight) in a black plastic bag and leave in the sun at least one week until the material is thoroughly dried. Hot composting gets the material up to 140 degrees Fahrenheit and kills the diseases too. • Grass clippings that have been treated with pesticides should be allowed to break down for 6-8 weeks before using. If pesticides were used, check the label for recommendations on when grass clippings are compostable after treatment.
For a short video on lasagna gardening watch Roger Reynolds and Shelly Ryan on Wisconsin Public Television http://video.wpt2.org/video/1572896528/.
Erin LaFaive is the Horticulture Educator for UW-Extension in Eau Claire County. Erin earned a M.S. in Environmental Studies from the Nelson Institute for Environmental Studies at the University of Madison-Wisconsin. She also earn a B.S. in Geography with an emphasis in Natural Resource Management at the University of Wisconsin-Eau Claire. Her coursework and studies focused on botany, ethnobotany, and citizen science.