Sheet Mulching with Greg Peterson
Building healthy soil is one of the biggest challenges in growing healthy food. Healthy soil is a balanced mix of: dirt, which contains minerals from broken-down rock; organic material like leaves, sticks and mulch; air space, so your soil is not too compact; living organisms like worms and microorganisms and, of course; water. My favorite and the fastest way to add oodles of organic material is by sheet mulching which, if you plan it right, can also be the most cost effective way to build the soil in your garden.
Sheet mulching or lasagna gardening is the simple process of combining different organic materials, most of which are readily available on or near most urban and rural lots. Not only does this process build incredibly healthy soil, it also adds a thick layer of mulch/organic compost to your garden beds to help retain water. Sheet mulching consumes a LOT of organic resources—think the green and brown leftovers from your garden/farm—so it is always a good idea to keep your eyes open for organic material such as leaves, small branches and grass clippings that a neighbor might be disposing of.
The good news is that, if you are starting a garden from scratch, sheet mulching gives you a wonderful jumpstart on building your garden beds; or, if you’ve been gardening for years, this method boosts your bounty because you build your garden right on top of your existing soil. This really nurtures the lazy gardener in me as in many cases there is no digging required. It takes a little work up front, but is well worth the effort and quite simple.
Step 1 – Finding your materials. There are many different materials that you could use in your sheet mulching process—the limit here is your imagination. As with traditional hot (thermophilic) composting there are two types of materials that you want to select: the greens and the browns. The greens are typically still alive and have a higher concentration of nitrogen, acting as the booster to jump start the breaking down process, and the browns are typically dried and higher in carbon. Generally, you need less greens than browns. A good ratio for them would be 30:70. However, this process is one of slow composing in place and the ratios are not all that important. What is important is that you have fun and get the job done.
- Green yard waste, leftover plant going to seed, grass clippings – minus seeds. This could include lettuce, okra, broccoli, or any other plants that have grown up and you have harvested from.
- Alfalfa hay
- Seaweed, seagrass
- Manure – cow, chicken, goat, or really most of the manures you might think of getting. Horse manure can be a little problematic as they do not digest the seeds they are eating. Hence if they are eating Bermuda grass and you use their manure you are giving the seed a huge boost in their growing process.
- Organic fertilizers, rock phosphate, bone meal, rock dust, kelp meal, blood meal
- Leaves, wood shavings, bark, pine needles, grain hulls, nut husks, spent corn stalks, get creative
- Straw, hay
- Newsprint which has nontoxic color (minus the glossy sections)but no paper that has been copied or printed on as it contains chemicals
- Cardboard, minus all packing tape
And my favorite – I purchase bales of straw and spread them in the chicken coop area as bedding for the chickens. Next, I add leaves, kitchen scraps, yard clippings and really everything else I can think of that the chickens might eat and I let them have at it for a few months. That way I have a nicely mixed bunch of greens and browns (remember they have been adding manure to the process) and I apply that directly to my beds in 6 to 12 inch layers.
Step 2 – Select a site.
It is best to pick a manageable site your first time around. In my video I started with a 5’ x 10’ garden bed. Remember: the bigger the site you are mulching the more materials you will need.
Step 3 – Clear the site.
This is very important, especially when it comes to removing noxious/invasive weeds. In our area this includes nut grass and Bermuda both of which need to be dug out strand by strand. If they are not they will likely completely take over your garden quite quickly. Most of the rest of the plants growing on the site can either be pulled up or cut off just below the surface and left there to rot.
Step 4 – Layer one: cardboard or newspapers.
This can be an effective first layer to help reduce the amount of weed seeds that sprout and grow up through your sheet mulch. One effective method of weed seed control is adding a small amount of organic fertilizer to the ground before you put the cardboard or newspaper down. This gives the seeds a boost and makes them sprout – then they hit the cardboard and give up. This is NOT a solution however for Bermuda or nut grass—sorry, but you have to dig them out!
Step 5 – Add a layer of browns.
Your first layer of browns can be made of pretty much anything from the browns list from above or whatever else you have that fits in the browns category. I have been known to put spent corn stalks, small fruit tree branches (smaller than a pencil), leaves, hay, straw. I usually take a little more liberty here as it will be the bottom layer as they will have a bit more time to break down. However stumps in the ground and larger branches are not the best things to use as they do take a significantly longer time to break down. Remember that the smaller the particles you use the faster it will break down. You want to create a layer of brown organic material about six inches deep before adding a thin layer of manure.
Step 6 – Add the greens.
The greens are the jumpstart for the composting process. They can include any of the green things that you can harvest from your yard, alfalfa hay, manure or organic fertilizer. When adding greens such as the bok choy I used in my video you can liberally add them. If you are adding manure or fertilizer, a couple of shovelfuls will do the trick. If you are using sheet mulching on a bed that has shrubs or trees, leave at least six inches between the mulch to the trunks of the plants, this will help prevent disease with the live plants.
Step 7 – Add more browns.
As I progress up through the sheet mulch layers I typically add smaller and smaller things, so no corn stalks or branches, only hay and leaves.
Steps 8, 9, 10 or more.
Repeat steps 5, 6 & 7 as many times as you would like. I have been known to build sheet mulch up to 36 inches. The cool thing is that as the ‘sheet mulch’ breaks down the bed sinks, in 6 months 36 inches of stuff becomes 2 or 3 inches of great garden soil.
Your Final Step.
Water periodically, this will greatly speed up the process.
Your Final Final Step.
Now comes the fun part—planting. Pick a place in your sheet-mulched garden, hollow out a bowl-sized area and fill it with some of your potting soil or compost. You can plant your seeds directly into this soil bowl and they will flourish, because this process provides breathing room for the roots as well as water retention. As the mulched area ages and shrinks, the plants will move down with the mulch and do just fine.
Sheet mulching is one of the easiest ways to create healthy soil that I have found. This process can be repeated on a yearly schedule until you are happy with the amount of growing soil you’ve gained. So sheet mulch to your heart’s content and grow some great veggies.