RRWA Environmental Column – May 2011
Sheet mulching allows you to compost existing vegetation in place, be it lawn or weeds, while keeping the existing soil intact. This helps suppress weeds, retain soil moisture, and eliminates the need to strip the lawn or apply herbicides in preparation of your new beautiful water conserving garden. Sheet mulching saves time, money, organic matter and topsoil, and helps create thriving new landscapes.
What is sheet mulching?
Sheet mulching is the process that is intended to mimic the natural mulching process in a forest. A common way to do this is to cover existing lawns or weeds with layers of compost (mow it first to knock down the height!), cardboard or paper, and then mulch. This layering system covers the existing vegetation and decomposes it in place to enrich the soil, provide a weed barrier, and retain soil moisture to lessen the water needs.New plantings are planted through the mulch, and you can make a small opening to accommodate established plants and trees.
What will you need?
Biodegradable weed barrier such as cardboard, or newspaper
Wheelbarrow, shovel, rake, etc.
Step 1: Measure the area & calculate quantities
Making an effort up front to figure out how much material you need will help you complete the project successfully. Cardboard or newspaper should be overlapped 4 to 6 inches to prevent weeds from emerging in open spaces. You will need enough mulch to cover the area to a depth of 3-4 inches.
Step 2: Site Preparation
If you are covering a lawn area, cut it very short. Other vegetation and weedy areas can be flattened or chopped down. In either case, leave the clippings on site because they will decay and add nutrients to the soil. Remove only large woody materials. Soak the ground with water to start the natural decomposition process and spread out 1-2 inches of compost (optional).
Step 3: Weed Barrier
Cover the area with the cardboard, or a 5-7 page layer of newspaper. These weed barriers are permeable to air and water and will eventually break down in the soil. Do not use plastic. Overlap the materials as noted above. Completely soak with water, but take care not to step on it after it’s saturated or you will create holes.
Step 4: Mulch
This top layer mimics the newly fallen organic matter in a forest. Good materials include wood chips, tree prunings, leaves or straw. The entire layer should be 3-4 inches thick. It will provide additional weed control, help retain soil moisture and give the area an attractive and finished appearance.
Step 5: Planting
Simply cut a hole through the weed barrier with a sharp knife or other tool and place plants directly in the soil under the sheet mulch. Be careful not to pile the mulch up around the trunk or stems to prevent disease. Also, don’t forget to add a little more water to each plant.
In time, all the added materials will decay and break-down into the soil, providing much needed nutrients for the soil, greatly reduced water usage, and a beautiful new landscape.
Find more information about sheet mulching and other sustainable landscape practices in the Russian River-Friendly Landscape Guidelines, available on line at http://www.rrwatershed.org/RRFLG/index.html
This article was authored by Damien O’Bid and Kevin Fredrickson of the City of Cotati on behalf of RRWA. RRWA (www.rrwatershed.org) is an association of local public agencies in the Russian River Watershed that have come together to coordinate regional programs for clean water, fisheries restoration, and watershed enhancement.