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Eliminating Lawn - #2     by Gila Shoshany

From our newsletters:

Eliminating Lawn #1             Eliminating Lawn #2           Eliminating Lawn #3 
Eliminating Lawn Without Digging or Using Chemicals

My own current garden was recycled from lawn by means of the tarp method described below, and was pushing up tomatoes, beans, perennials and annuals in the same summer as the lawn was eliminated. But I was extremely lucky—my lawn happened to be a converted hayfield that had never been chemicalized, and that had been mowed for 30 years and more as a suburban lawn in an post-war subdivision in the Midwest. Depending on what kind of lawn you're starting with, eliminating your lawn without digging or a shovel can take a few weeks, or it can take a few years.

A thick manicured lawn with two species of grass and no weeds is unquestionably the result of a chemical miracle. A scraggly lawn with dandelions, chicory, clover, ground ivy and violets sprawled in what is left of the grass, is unlikely to be chemicalized, but more likely to turn up old boots, broken glass and the like. Neither one is ideal—the chemicals residual in the “perfect” lawn are not likely to let vegetables or ornamental grasses thrive until several years have passed, while boots and glass are not a desirable growing medium. A third common problem: the lawn may actually be growing in a thin layer of top soil laid over a substrate of the “builder’s soil” created by the heavy equipment used to build the house.

Tincture of time is the solution for all these problems. You might have to repeat the processes laid out here several times until the earthworms and bacteria once again act in a natural cycle, or until enough organic matter has been incorporated to dilute the old boots or subsoil into something more like garden soil. If your soil is good, these methods will take several weeks in the spring or summer, perhaps. But, if your soil is poor, and you choose these methods, then you must realistically expect to trade in your shovel for a year or two of patience.

Eliminating a Lawn by Sheet Composting Under a Tarp:
(for use in an open area away from trees)

Sheet composting under a plastic tarp will eliminate sod easily, but can only really be used in an open area away from trees (and away from any other plants you want to save.) You might use this method in the middle of a suburban lawn to create space for a vegetable garden or ornamental planting. Or, you might want to convert rough land (pasture, old hayfield) to friable, tillable ground without actually tilling. The below amounts of bulk organic matter are for a roughly 20 foot x 25 foot patch. Scale up or down as needed.

How To:

a. Make the existing vegetation lie flat (trample it, mow it, string trim it).

b. Dump whatever BULK organic matter you have on hand onto the area, and spread it as evenly as you can. (Note: If you can’t readily get bulk organic materials, keep reading, there is a modification to this system that might work for you.) Your coffee grounds and orange peels don’t count as “bulk materials:” an ordinary household is never going generate sufficient kitchen waste. For a 20 foot x 25 foot plot, the ideal amounts in contemplation might be:

  • A dump truck (not pickup truck—a dump truck) full of sea- or lake-weed. A dump truck load seems like a lot, but water weeds have a great deal of moisture.
  • 15-20 leaf bags full of autumn leaves de-clumped and spread evenly
  • 12-15 bales of straw, opened and fluffed out, then trampled down into an even layer.

The above are ideal amounts. Half these amounts is acceptable, but much less will simply disappear without much of a trace. Hay is not a wonderful material to use because it contains weed seeds but if you have nothing else, go for it. Wood chips, cocoa hulls and other ultra-dry materials don’t work very well with this method, because they take too long to break down. Except for avoiding very dry materials, however, it doesn’t matter very much what organic material you use, and the more organic matter you use, the better the results. If you want to use a concentrated soil amendment (blood, bone or alfalfa meal) or if you need to add lime to an acidic soil, sprinkle the amendment(s) on in layers with your organic matter—like a soil lasagna.

c. Make the bulk organic layer very wet all the way through A good soaking rainstorm is best, and you can simply leave all this laying out until a good rainstorm comes along. However, if you’re impatient, or live in a dry climate, then leaving the sprinkler running full tilt overnight would achieve the same effect.

Gila is sheet composting in her backyard

d. Lay a tarp or overlapping tarps over the area, and weigh it/them down along all the edges (otherwise the tarps will sail off in the first stiff breeze). Throw a couple of weights in the middle of each tarp, also. If you have nothing better with which to weight the tarp(s), use clods of soil dug up from the plot.

Why it Works:

Sheet composting under a tarp works because the tarp traps both moisture and heat. Hot, dark moisture is one of the very best conditions for rotting. On a sunny summer day, temperature under the tarp will soar within minutes. In spring, fall or winter, the temperature will go up more slowly, but even so, on a crisp sunny fall day, you’ll probably see the sheet of organic matter steaming if you pull back the tarp. In summer, you could expect that in 2-4 weeks, the organic matter will be a rotting, the earthworms will be in overdrive, and within 3-5 weeks, you’ll have a patch of bare earth covered with a crust of organic matter, and no plants still living in it. Things will go faster if you pull the tarp back when a rainstorm is expected, or pull the tarp back and soak with a sprinkler when the organic material gets dry. Remember to cover up again as soon as the rain/watering ends to trap the maximum amount of moisture and heat under the tarp. After a week or two (summer) you can also speed the process along by roughly digging in some of the organic matter. This kind of rough mixing spreads soil bacteria up onto the organic matter, and speeds decomposition. If you know someone whose (organic) garden you particularly admire, beg a bushel basket or two of soil (if they’ll let you have that much) and sprinkle that about too. Whatever beneficial soil bacteria they have going will be added to your soil under very favorable (warm, wet, dark) growing conditions.

If you tarp your plot in spring, fall or winter, you must leave the tarp on until you get the results you need, and the time can vary greatly—if you do this in late spring and you live in a warm climate, it might go almost as fast as in summer; if you do this in fall and you live on the Canadian border, you might have to wait until the next spring, or even early summer, until the sun is high and hot enough to do the work of rotting the organic matter and activating the worms.

If you leave the tarp on until the organic matter is really rotted, and even until the underlying soil becomes heated through for several inches, there’s an added bonus: heating substantially reduces weed seed germination rates and viability. This level of heating is called “solarizing” your soil. If you’ve used hay for your bulk organic matter, you really must leave the tarp on until the entire layer of hay, as well as the top few inches of soil are solarized. This will deactivate all the weed and grass seeds which were in the hay. To be certain the seeds are really dead, it would be best to take off the tarp, toss the layer of hay around with a hay fork, re-water, re-cover and re-solarize.) Solarizing soil also reduces the viability of insect eggs and grubs

An aside for vegetable and annual gardeners (or those rejuvenating an exhausted perennial bed, but take the perennials out first…) Sheet composting under a tarp works very well as an annual treatment for a vegetable or annual garden. There is no need to do a fall clean up—just dump bulk organic matter right over all the old bean vines and dead tomato plants, rotten onions and missed potatoes. When the cold rains have come, or a solid snow cover is on, and the area is as wet as it is going to get for the winter, cover the area with the tarp and weight it. Admittedly, when you’re out there in mittens and Sno-Pac boots trying to spread a stiff crackling tarp in the fading light of a late January afternoon, you’ll wonder if my advice is really sound. But next spring (later in the spring—not in time for the peas, but in plenty of time for the tomatoes and beans) you’ll pull back the tarp to find last year’s old plants and rotten produce are reduced to the stray tomato vine skeleton, your eggplant will not suffer from flea-beetles, cabbage looper eggs will not hatch, soil borne diseases are much reduced, and your soil is warm and ready for planting, maybe even 1-2 weeks before untarped soil would be ready (and certainly 2-3 weeks before heavily mulched soil would be ready because a heavy layer of mulch keeps the soil cold longer into the spring).

Like everything else in life, sheet composting under a tarp does have a price. The extra heat generated under the tarp rots the sheet of organic matter into the soil, but it also burns out soil organic matter rather quickly. Ultimately, this is a good thing, because humus (organic matter which cannot be further decomposed) is actually the best possible soil amendment. Burning large amounts of organic matter into your soil with solar power under a tarp will create humus at a great clip. However, the downside is that you really need to have access to generous amounts of bulk organic materials to make this method work.

If you want to install a more-or-less permanent mulch layer on an annual or perennial garden, but have a hard time getting lots of bulk mulch materials, you must modify this method, because otherwise it will quickly burn up your mulch. In this mulch-preserving modification, you tarp an area of sod or old pasture into bare soil without adding any organic materials at all—if you wet down the sod very well, then soak it again after 5-7 days, the sod will be dead under a tarp in about 1-2 weeks in high summer. Next, remove the tarp, add a mulch layer over the top of the dead sod, then push aside the mulch in the desired spots, and plant vegetables or ornamental perennials through the mulch layer and into the now-dead sod and the earth beneath. (In my experience, it’s a lot faster and less hair-raising to put the mulch down first, push it aside and plant through it, than to plant first, then try to mulch around new little plants.) Because the mulch is never placed under the tarp, the mulch isn’t burned up by the heat and moisture. Of course, you also don’t add as much humus to the soil as you do by putting the mulch under the tarp to heat and rot, but the mulch lasts a lot longer, so there is a lot less hauling around of bulk organic materials.

--Gila Shoshany
Madison, Wisconsin, USA