Water for landscape and lawn use may not be as critical an issue in other parts of the country as it is in the Western states, but the use of fertilizers and pesticides, electricity or gas to mow, and labor to care for lawns are universal issues. If you’re thinking of retrofitting an existing lawn, your options for design are many, but you still have the starting point of: “What to do to get rid of this big green carpet?”
As a small scale residential practitioner, I work with many Do-It-Yourself clients who want very much to tackle their landscape retrofits themselves. They want to save water and are tired of either paying for a Mow-Blow-and-Go service or mowing the yard themselves. Also, they are often ecologically-minded people who don’t like the idea of all that sod going to the landfill. Not to mention that most suburban landscapes have been completely scraped clean of any decent topsoil when the houses and yards were put in. To further scrape off the precious little soil and all the valuable green matter in the lawn and root zone under the lawn with a sod cutter would be a waste.
The sod cutter also uses energy in the form of gas and oil, is heavy to handle, requires a truck to haul to the site, and can compact the earth under its blades. So, how can you compost the lawn in place, retain the nutrients on site, and keep down the complexity of the project? Sheetmulching! Born from the practice of Permaculture which advocates saving resources while layering uses (such as building an arbor out of recycled wood to provide shade as well as support for the grape vine, which in turn provides food), sheetmulching is a method of covering the lawn or weedy area with paper products, thereby letting the moisture in and keeping the sun out. The paper is then capped with mulch, which kills the lawn in a matter of weeks.
The paper products can be recycled cardboard from bike stores, appliance stores, or moving day. They can also be multiple sheets of newspaper wetted down with water to keep the wind from making a kite out of them. Then begins the composting process. I recommend that clients contact the arborist who cares for their trees to provide a truckload of chipped tree mulch to go on top of the cardboard or newspaper to a thickness of 4-6 inches. They will often provide it for free. The paper will decompose along with the lawn and can stay in place. No “Round Up” is needed, and the lawn can be living or dead before starting the process. Sheetmulching can be done any time of year, but it’s helpful to have some rain or moisture to aid the composting process and keep the mulch from drying out.
You may also add a layer of your own composted material or purchase commercial compost to add the mycorrhizae and other nutrients to kick start the composting process. If you’re impatient to begin installing plants to replace the old lawn, you can plant right into this cardboard layer by cutting an ‘X’ through it, pouring in some new soil to cover your new plant’s roots, and plopping the plant right in. Fold the cardboard over the rootball and tuck the mulch over the cardboard.
Most of the clients I work with want to get rid of the entire lawn, so if they have an irrigation system, retrofitting the irrigation is as easy as cutting off all the spray heads except one, and so the remaining head and valve will provide drip irrigation for the new, drought-tolerant garden. Some folks still like that little slice of green, so you should use landscape paint on the lawn to draw a diagram showing the existing watering limits of each spray head. Then, all the heads not watering the desired slice of lawn can be shut off. That way, no excessive digging is needed to shave off one or two spray heads. In clay soils, no digging is a big bonus.
If hardscape borders the existing lawn, be sure to take care so that your mulch sandwich doesn’t run over onto the sidewalk or the neighbor’s driveway. Digging down along the edge of the hardscape a few inches and then pulling up the sod pieces in 12 inch x 12 inch chunks is sufficient to get the cardboard to lay below the edge of the hardscaping, and therefore giving the mulch somewhere to go.
If you are doing the sheetmulching for a client, a landscape construction crew that uses locally-available rolls of cardboard can also accomplish this process. You will have to make some calculation for the first project to estimate the job cost, and you will also have to educate the workforce to do this successfully. But the process is so simple and resource-efficient that it’s worth the extra effort on the first few jobs. No dump runs! No scraping and cutting! And if you’re ready, no waiting. You can install plants in the sheetmulch the very same day.
The sheetmulching process is highlighted in a YouTube video at: http://www.youtube.com/watch?v=4PB0Ym_iXmc.
by Kat Weiss, ASLA
Kat Weiss, ASLA, is the owner of Kat Weiss Landscape Design in Livermore, California, and provides services in the San Francisco East Bay area. She can be reached at: firstname.lastname@example.org.