This week I got a complimentary copy of Urban Farm, dedicated to “sustainable city living.” The cover story is Lasagna Giardino – follow this recipe for a lasagna garden that grows perfect plants – Italian or not.
This is not a new idea, but was popularized several years ago as a way of preparing soil for planting. The article relates the steps:
1) Prepare the ground by mowing the lawn
2) Dig up the first 12″ of soil (double digging)
3) Place a layer of “noodles” (paper and cardboard are popular) – the low nutrient material
4) Place a layer of “sauce” (the green material)
5) Repeat as often as you like and “let it cook”
I like the first step of this. But my second step would be:
2) Add a thick layer (12″) of arborist wood chips and “let it cook.”
Double digging the soil 12″ isn’t necessary: we do it because it’s hard work, and we think we need to put elbow grease into the project. Making layers of noodles and sauce isn’t necessary: we do it because appeals to us -lasagna is a tasty comfort food.
There’s a lot of damage that this “recipe” can cause. Double digging the soil 12″ destroys soils structure. Don’t do it. The layers of noodles and sauce (especially the sauce) can create an overload of plant nutrients. Furthermore, the “noodle” layers – the sheet mulches – impede water and air movement. They’re not needed to keep the grass from growing through. Wood chips do this just fine on their own. And don’t worry about that initial 12″ of chips. Within a few weeks it will settle to about 8″. Let it sit for several weeks. Then pull aside some of the chips and take a look. If the process is done, the grass and/or weeds will be dead and decomposing – a natural compost layer. You can then plant whatever you like. Reuse the chips somewhere else in your garden.
It doesn’t look like lasagna, but it’s a heck of a lot easier and more closely mimics a natural mulch layer than lasagna does.
Does your recommendation against double digging apply to traditional gardens also? I ask because the only areas of my gardens that have thrived with little additional work are those which I dug 12-15″ deep and worked in compost, peat moss, and woods humus, probably 25 years ago. Those beds are still friable and only need a light top dressing with fertilizer and mulch whereas all other beds require much more work annually to keep them growing well. One which was built using a traditional lasagna “recipe” about 10 years ago is now almost back to the original condition. (Our native soil is an acidic clay with a very thin layer of topsoil.)
Sandy, double digging (the equivalent of tilling in agriculture) disrupts natural soil building. No-till agriculture is increasingly preferred as being more protective of the soil ecosystem. I think the same philosophy could be applied to home gardens as well. You’re right, you can boost production with a more aggressive approach to soil amendment – a similar argument is often made in conventional agriculture (compared to organic agriculture) to till, use excessive fertilizers, pesticides, etc. I guess it depends on how you regard the soil – as a medium for growing vegetables or as an ecosystem (and I’m not being judgmental). It’s a philosophical choice.
Personally I prefer the herbicide and mulch method but I have some clients that object to the use of roundup so I find certain parts of the lasagna method – call it a ‘diet version’ – that are effective. For proposed sites where there are a lot of weeds I like using the paper or carboard method and then adding woodchips. Afterwards I let it sit like that for about 6 weeks before planting. It sure beats rototilling or double digging – which agree is ridiculous.
Forgive me going off topic , but as a city dwelling GARDENER i find the term urban farm/agriculture foolishly pretentious. I wonder what terms these “urban farmers” would come up with for staking tomatoes or deadheading roses.
I’ve done lasagna gardening or a really modified version in Panama (home of slash and burn agriculture and low organic content tropical soils).
It was recommended that we dig down 18 inches, and then layer in ash, chopped up banana plants and leguminous tree leaves between layers of the native clay soil.
I didn’t notice an increased fertility of the soil in the bed I tried in my own front yard. Eventually I gave up and just made quick compost and grew my vegetables directly out of that.
What would you recommend to improve soil fertility quickly in a garden?
Adding a layer of compost to the soil as a mulch is a great way to improve soil fertility quickly. The difference is letting nature do the incorporation (through animal activity and rainfall, for example) rather than disrupting the soil ecosystem.
For quite a while we have just rolled round bales of hay over the area we grow tomatoes, peppers, cucumbers, squash. We do this by hand to avoid compaction by equipment and we roll it out pretty thick. Over time we have built up a wonderful soil with good tilth. I just pull back the hay a little and plant the seeds or plants where I want them. Also keeps the weeds down to a very manageable level.
I have recommended “lasagna garden beds” to my fellow gardeners for years. I have never recommended double digging. Layers of newspaper, arbor chips, soil, sand, compost, wood ash, etc. have created wonderful, friable, pH-neutral beds on top of otherwise terrible sites. Around here, typical soil with pH less than 5 is very thin on top of sheets of rock that go on forever. The advice here is to create workable, and fertile beds on top of existing conditions – not to beat ourselves up trying to break through the tough stuff. I let worms and strong, soil-busting roots work for me in that regard. Gardening is a pleasure not an overwhelming, self-defeating task.
My favorite planting bed preparation is to designate the area to become the new bed, cover it with corregated cardboard from boxes without a lot of colored printing on them, hold cardboard edges down with rocks, cover cardboard with wood chip mulch, let steep until weeds and grass are dead and worms have worked the soil (usually the cardboard has decayed), plant, remulch. Voila. I spend more time enjoying my gardens, my back does not hurt, and I’ve not destroyed messed up layers of soil.
What do you think about a broadfork as an alternative to double digging? At least in the case of heavily compacted soils?
Erik, a broadfork is certainly less destructive than double digging, so if I felt the need to aerate a bit (and couldn’t mulch for some reason) it seems a good alternative.
And I did see your article! Thanks for helping get the word out on the importance of university extension research and education.
Sorry for the double comment! Forgot to say thanks for your participation in an article I wrote in the same issue of Urban Farm. And to veggie&roses–point well taken. Though I write for Urban Farm I call myself a gardener.
We’ve got a big pile of wood chips from a tree we had cut. But it wsan English walnut. I’ve read that walnuts have allelopathic properties. Are the chips safe to use as mulch? Will they become OK if alowed to sit for a while?
Christine, there isn’t any practical research to show that these chips would be a problem as a mulch. However, I would play it safe and only use them around established plants (not seedlings). Even allelopathic plants have a tough time killing off mature competitors. It’s only seedlings that tend to be affected. And yes, if you let the chips compost a while, the juglone will break down.
Will all those wood chips attract termites?
Betty, research has shown that termites really don’t like wood chips. They prefer mulches made of paper and cardboard, presumably because they’re more digestible.
Would lasagna gardening be effective for weed control if the layer of cardboard was covered by a layer of straw only?
Jim, the straw wouldn’t really make any difference. The trick with weed control is to keep light away from seeds (or root crowns in the case of perennial weeds). Cardboard does this on its own, but it also inhibits water and air movement. Thick coarse mulches will restrict light penetration to the soil, but won’t interfere with water and air exchange. And while cardboard and newspaper eventually break down, until they do they are impacting the entire soil system – a broad spectrum kill, rather than targeted towards weeds. Rather than kill off the local soil ecosystem (or at least stress it unnecessarily), we should choose methods that target the problem.
Last summer, we filled a huge hole with 3 dump truck loads of sand. The hole appeared when the house was five years old. (The builder buried all the trees on the lot when clearing the half acre for the new home.) After last years record snowfalls the hole sunk again about 2 more feet. So now we’re trying to figure out how to get the last 2 feet filled with manmade topsoil. We have over 40 bales of seed filled straw and had 1 dump truck load of mixed cottonwood shavings and chips and have a 10 foot pile of branch trimmings (mostly dead wood from willow and cottonwood). So our first “layer” is 10 feet of pure gravel put sand. Think we’ll put the entire pile of brush down next. Then what? Should we layer the straw between the green cottonwood chips all freshly cut yesterday? Should we set aside some of the sand to layer that between cottonwood layers too? How can we speed the composting process up with our average summer temps being only 60 degrees? We are trying to get a small pickup load of aged horse and chicken manure this week to either layer that in with the chips or to add to our separate compost pile that can’t get above 80 since last fall. Help. We don’t want the chips too close to the house where we have dandelion patches for fear of attracting too many ants or slugs. So how can we eliminate all the weeds with all this stuff rapidly? Is the cottonwood too fresh to use as a mulch around the already planted blueberry and raspberry patch? Do we age it first?
I would caution against putting thick layers of organic material within your soil profile. They will decompose (just like those trees did) and your yard will continue to sink. You need no more than 10% organic matter within your profile – that’s what’s generally sustainable around Anchorage (my guess as to where you are located). Therefore, you should use a soil mix that mimics a natural loam – primarily sand, about 20% v:v screened clay, and 10% v:v organic matter. That would pretty much mimic a sandy loam. Save the rest of your organic stuff for topdressing the bare soil to protect it from weeds, compaction, etc. Put the richest stuff down first as a thin layer, then your coarser material. The mulch layer textures should resemble what you see in a forest duff layer. It doesn’t have to be aged first, since it’s a topdressing.
My question about the lasagna method has always been what happens over time. Sure you may get a year or two of “weed-free” gardening. But what happens when weed seeds blow in and sprout in that layer of rich, friable organic matter you’ve made. I garden in a rural area where evil goldenrods and mile-a-minute run rampant.
I think it is interesting how often I read about using newspaper or cardboard. Most people trying to use a lasagna garden are also trying to use natural, organic materials. What about all that glue in cardboard? That doesn’t seem very natural to me. I’m really glad you talked about how the wood chips, or other layers, will easily smother the weeds or grass growing on the ground. There is no need for cardboard, and wood chips are a great natural alternative. Just don’t use cedar!
Is cedar really a problem?
I got a truck load of woodchips a couple months ago and have been using it in lots of areas of the garden, as well as making paths. There’s definitely a lot of cedar–I’d guess close to half (actually chamaecyparis and thuja most likely).
I do see smears of white stuff, presumably a fungal something, as I dig around now to plant, but the turned-ever turf is pretty much broken down. And there’s an interesting fungal “sheet” growing on the remaining mountain of woodchips today–looks like yeast that’s foaming in a bowl waiting to be added to the bread mixture, only solid.
So, is cedar OK?
Cedar chips are just fine. It’s a myth that they will kill plants. See this online article: http://puyallup.wsu.edu/~Linda%20Chalker-Scott/Horticultural%20Myths_files/Myths/Allelopathic%20wood%20chips.pdf.
Where I live, in southwestern Ohio, the developers scraped all the topsoil up and sold it before they built the houses. Apparently a very common practice here, and perhaps elsewhere too. So I have a thin layer of crappy sod over a dense highly alkaline sandy/clay subsoil. My strategy is to try to create good gardening soil by adding lots of wood chips, and tilling them several inches into the compact subsoil. There doesn’t appear to be much native soil ecosystem present; there’s hardly any organic matter in this light tan subsoil, which also contains lots of chunks of limestone. I’m hoping to re-establish something like the soil that accumulated here after the glaciers retreated, but in only one year instead of 10,000. What do you think?
Ted, I’d only till in composted wood chips, and then only about 10% by volume. Fresh chips will tie up your nitrogen if you till them in, and you don’t want to have too much organic in your soil (it’s not sustainable). But even better, I’d avoid tilling altogether. It destroys soil structure. Just let it develop on its own.
I know this is an older post, but I have a yard full of weeds that I need to get under control and want to avoid chemicals. What time of year is generally best to put down the thick layer of wood chips in the Pacific Northwest?
Adam, if they haven’t started growing yet do it now. Mow the area to the ground, then chip. if you can afford to wait until summer when everything is pretty dry, it works even better. But as long as you use a thick enough layer now, and mow it flat, it will still work.
Thank you Linda for continuing to reply to these posts! I have learned so much 🙂
I live in southern New Mexico where the soil is extremely alkaline and has very little organic matter. I can see from your replies that you consistently advocate for not using cardboard as an initial layer due to it disturbing the micro-organisms that live in the soil. I am also an advocate for using the earth’s own energy for gardening and not working against it 🙂
My question is what to do about very compacted, rocky, non-organic soil full of Bermuda grass? This is the only area sheltered enough from wind to viably grow a garden. I was planning on using cardboard but since reading this post, I am a tad lost on how to maintain the microbiology of the soil but not have Bermuda grass growing through it for the duration. Any help is much appreciated! Thank you 🙂
Hi
I have used the lasagna method in an old hayfield to create low raised garden beds. I did double dig as the soil was extremally compacted. In this situation do you think I should do the double dig? We are still making more beds, it’s a large garden and it would be great if I didn’t need to double dig.
I would suggest covering your compacted area with a very thick layer of arborist wood chips. This will allow the soil to decompact naturally. After a month or so you can move the chips aside and plant. This method preserves soil structure and soil organisms.
I love this blog and this particular conversation. I garden in Chapel Hill NC and have clay soil. I have a new perennial garden and have been using shredded leaves and wood chips for mulch. When I plant a new shrub or perennial, I’ve been digging a hole, adding some compost and Permatill and then planting. Does this sound right or is there something i should be doing or not doing?
thanks!
Laurie
Hi Laurie –
You shouldn’t put anything into the planting hole except the roots of the plant and the soil that came out of it. Roots have a difficult time getting established when there are soil textural differences to overcome. Take a look at this link: http://puyallup.wsu.edu/wp-content/uploads/sites/403/2015/03/soil-amendments.pdf
And thanks for your kind words!
Thanks – as I say when in Mexico about my spanish, “Estoy aprendiendo”- I am still learning!
And one more- how about improving drainage in this clay soil for my perennials?
The best way to improve drainage for a permanent bed is to prevent compaction. We also have clay soils and the best treatment has been mulching with wood chips and letting plant roots do the de-compacting.
Hi there,
I am starting a new bed in a new-ish subdivision with heavily compacted clay soil. I am going to put the wood chips on top of the sod to kill the grass. Should i put a layer of compost on the sod first to speed up the process?
Also, if i let the garden sit with wood chips on it for a year before planting, would the soil become more manageable(as in improving the soil structure)?
When you first apply wood chips, adding some compost is a nice way to get the process established. With time, your chips make their own compost layer. And yes, you will be amazed at how much your soil tilth is improved after being protected with the chips for some time.
Thank you! I’m excited to give this a try! No more digging!
What is your recommendation for people that want instant garden beds where there is currently a lawn? I’ve tried renting a sod cutter and then adding topsoil, but this is quite labor intensive.
There is no “instant.” We have to start thinking about what’s naturally possible and sustainable over the long term. Soil disruption is bad, period. Killing weeds naturally by restricting light is the best way to go. If people want an instant garden they should either use container plants or plastic ones.
I have a business to run and although I agree with your philosophy – my clients don’t. As I’d rather not have them go to another business who is more than willing to do anything they ask for, what is another option for creating garden beds from lawn?
I would try to persuade them to go the mow and mulch route (if you haven’t seen that post search “how to kill your lawn” in the search box. They can still buy the plants they want and place them in different areas of that vast sea of chips. Now is not the time to plant, anyway – it should be done in the fall for best root establishment.
Other than that, I can’t recommend anything that is based on plant and soil sciences. If they aren’t interested in that I would just do whatever they ask you to do so that when things fail it will be their fault, not yours.
This is a great article and thread! I live in Northern NJ and we typically get a lot of rain. We have sandy soil and lush lawns with a lot of clover and plantain. I have done lasagna methods with cardboard and organic matter – but have a huge bug problem. There are also tons of slugs. To expand these garden beds is the best thing just a thick layer of mulch? Should I remove the existing lasagna bed material to the compost pile?
Thank you,
David
Remove the cardboard and throw it away. Don’t compost it.
The lasagna method can lend itself to slug and bud infestations by creating pockets within the layered materials. These spaces give pests a place to hide.
A thick layer of mulch can help with pest control but slugs will still travel over it. Hand picking or beer traps work well for control.