Wednesday, November 15, 2017

Lasagna Gardening Might Be The Answer To The Question You Didn't Know To Ask

For the homeowner who doesn't spend hours each week immersed in gardening journals, tweets and blogs, the term "lasagna garden" probably conjures up visions of tidy plots of Italian herbs and Roma tomatoes. But lasagna in this case refers to the process, not the product, of the garden. Also known as "kill mulch" or "sheet mulch" gardening, lasagna gardening is a no-till method which uses layers of mulch and compost to create a stratified growing medium while simultaneously enhancing the underlying soil.

I stumbled across the idea a few years ago while, ironically, expanding my Square Foot Garden. I wanted to reclaim space for several new raised beds from my lawn and didn't want to use any sort of herbicide to kill the grass. I got the bright idea of cutting the grass as short as my mower would allow, then covering it with a layer of newspaper and several inches of shredded leaves. It was a fall project and effectively allowed me to kill two birds with one stone. My intent was simply to kill the grass in a natural way, but when spring rolled around I was surprised to see that the creeping myrtle from an adjacent bed zoomed in to cover the unused spaces. A little digging on the Internet confirmed that I was not the first to discover this concept and that, in fact, versions of the method had been in use for hundreds of years. Some additional tinkering led me to a system that I am confident is repeatable and will work well for just about any garden situation.

Now, you may be asking, if you are a proponent of Square Foot Gardening (which I am) then why are you promoting a different method? There are two answers to that question. First of all, while you can grow ANYTHING in a Square Foot Garden, some plants are not very practically grown that way. The "umbrella" squashes like zucchini, for instance, are just not well-suited for that method, as even the smaller hybrids will quickly grow to cover an entire raised bed. Second, the initial investment required for a larger Square Foot project can be prohibitive for some gardeners. Yes, it is true that a 4' X 4' Square Foot Garden will produce as much as a larger row garden, but it will also cost around $100 to build. For hobby use, there is a justification for that cost in terms of seed, water and fertilizer savings, but for a larger scale or semi-commercial gardening operation those costs get out of hand very quickly. So, what I have developed for the cost-conscious gardener is something of a hybrid approach which incorporates some of the advantages of the Square Foot method with the minimal investment of the no-till lasagna method.

Fall is the best time to start a lasagna garden, since there is a ready supply of fibrous mulch (shredded leaves) and the time between now and spring planting will give the garden time to "age." As implied by the term no-till, there is no digging required to start, the garden is built on top of the ground. The first step is to lay out the area that will become the garden. Following one of the Square Foot principles, the area can be any length but should be no more than four feet wide -- 4' X 8' or 4' X 10' are good to start -- and there should be at least two feet (I prefer three) between the beds. I use mason's line and landscape pegs to define the area and then use a lawnmower or string trimmer to cut the grass inside the lines as low as possible.

Next, place a layer of newspaper 2 or 3 sheets thick directly on the grass/ground. You will want to wet the newspaper as you are laying it to prevent it from blowing away and to begin the decomposition process. Once the area is completely covered in paper, add a layer of organic material eight to ten inches thick on top. You can use just about any organic material available to you including shredded leaves, grass clippings, coffee grounds, shredded newspaper, etc. While you should try to have some of both "brown" and "green" materials, there is no particular formula you need to follow. If you are using shredded leaves almost exclusively, however, you may want to add a little blood meal as a source of additional nitrogen. 

Again, to prevent the material from moving and to help start decomposition, wet your "stack" thoroughly at this point. It is okay to leave the stack at this stage for a few days or even a couple of weeks. As the material settles and begins to decompose, the stack will decrease in height and it's okay, although not necessary, to add another couple of inches of mulch as is does.

The next layer can be either a single layer of corrugated cardboard or a layer of newspaper five or six sheets thick. Be sure to use only uncoated cardboard as the glossy type does not decompose well. On top of the cardboard or paper, add a layer of good quality compost two to four inches thick and water the whole stack thoroughly. From this point all you need to do is wait for spring! Your seeds or seedlings will be planted in the compost where they will grow down into the decomposing mulch. Worms will be attracted to the rich organic matter and break up the underlying soil in the process. Weed growth will be minimal, just as in a Square Foot Garden, and you can even use the Square Foot planting rules as a guideline for your lasagna garden. Each fall, a new layer of mulch and compost will be added, maintaining a permaculture cycle. 

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