I cannot take responsibility for writing this. However, I thought the information was very important and should be shared.
Text inside spoilers to make it easier to read.
I suppose I should explain what sheet mulching is, and why its important before I go over the steps eh?
What is it?
Sheet mulching is a practice which harnesses the goodness of large volumes of organic material collected in your own yard and neighbourhood to create rich, healthy soil for your garden plants (this material often ends up in the landfill or the curbside yard trimmings collection program). It is a layering technique that sort of resembles an “organic sandwich”, with the actual sheet mulch layer itself being the secret – it actually blocks out weeds and encourages the development of wonderfully nutrient-filled soil. The following sections will tell you how to do it, step by step.
Why Sheet Mulching?
The benefits to sheet mulching are many and varied. Here are just a few:
- It Requires LIttle Labor – Who doesn’t want to enjoy their garden more and sweat over it less? With just a little preparation, sheet mulching will allow you to do just that.
- It Builds Soil, Adds Rare Micronutruients, and Prevents Erosion – The key to a garden worth showing off is not fertilizers and pesticides but rather rich, healthy soil. Sheet mulching can help you get it!
- Recycles Waste – Processing organic waste is extremely costly, even if it’s composted through your municipal yard trimmings collection program. By processing it at home into something useful, you are saving resources and money (read “taxes”) for the municipality, and therefore for yourself.
- Reduces Watering – As our population grows, water conservation is becoming more and more important. It is important that we all think about how much water our gardens use so as to lower our collective impact.
- Bioremediation of Toxic Soils – An inexpensive way to return sick soils to health.
Nitrogenous Materials:
You can source these materials from your own yard,or from neighbours’ yards (i.e., ask them to save their lawn clippings and weeds for you for a couple of weeks pre-mulchin – just make sure they aren’t using pesticides in their yard). The idea is to not have to go too far from home to complete this project. Here are some ideas and tips:
Grass clippings: Collect them early in the spring and summer and store in an old garbage can – it will smell strongly. At this time the grass has no weed seeds and is very high in nitrogen – it is useful in the garden during the growing season, but can kill small plants (also be sure there is no dog feces in the grass, as it is a serious problem for salad and root crops and not nice to have around).
Seaweed: There is some controversy about this particular material, as using it removes nutrients from an already impoverished ecosystem (i.e., urban beaches). Try others instead.
Soya grits: Grits are what remains after the soya beans are pressed for tofu. They are high in both nitrogen and phosphorus. Contact local soy processors for sources.
Death Bucket: There are quite a few weeds that will overpower a cold compost, even in the dark. Try putting them in a large bucket of water (with a lid – try an old garbage can) and setting it in the sun. Usually after 2 warm months the roots are dead. Couch grass, canary grass, forget-me-not, bindweed, horsetails and anything in seed works well. This stinky mixture is high in nitrogen and nutrients thanks to the weeds’ hard work. Be sure not to leave it around during the spring or summer as it is a breeding place for mosquitoes.
Compost with Unfinished Kitchen Scraps: These are good, especially when there has not been enough carbon introduced to the compost or it has been too wet. It will be rich and stinky and full of nitrogen (do not use fresh kitchen scraps, as they will attract animals).
Chicken Manure: When it’s fresh is when it is the strongest. It is the most nutrient-filled nitrogen and phosphorus source known. As it is so acid, lime is usually added to reduce the acidity, and to prevent the nitrogen from breaking down. After it is composted it is usually easier to use and less likely to burn your plants (this happens when too high a nitrogen source is introduced to plants) or smell strongly.
Horse Manure: Often what is sold as horse manure is really a pile of cedar woodchips and a little old manure. The cedar has alleopathic (poisonous) compounds that stop the growth of most plants and it breaks down very slowly. The horse manure actually has very low nitrogen levels to begin with, and after only one season there will be very little nitrogen left, with the woodchips pulling out whatever remains. Try to source pure manure from local stables or horsekeepers (try LauraLynn Stables at 604.986.8714) and then plan on using other materials to get the nitrogen in.
Alfalfa: Feed stores often have broken or rotten bales that they will give away.
Nettles: A good source of nitrogen and iron but difficult to handle. The plant proliferates by spreading roots and can quickly get “out of control”. Not recommended for small gardens.
Comfrey: There are three different species that are common. Comfrey is a spreading weed in some jurisdictions and it is difficult to clear an entire field when it is well established. The recommended variety is a Russian Comfrey variety called Bocking #4, as it has the highest nitrogen and phosphorus levels in its leaves and has sterile seed. It can be propagated from its roots. Comfrey is considered a permaculture wonder-plant. Call Edible Landscape Creations to purchase some plants for your garden – call 604.645.9529.
There are many other sources of nitrogen. Just become aware of what is around your home and the homes of your neighbours.
Carbonous Materials:
Straw,hay,woodchips,hedge trimmings (not too much laurel or cedar), leaves, tops of perennials in the fall, sawdust, cotton and wool clothing, ruined futons (really good source – peel the layers off and use as sheet mulch!), bracken and sword ferns, pampas grass and other big grasses, bull rushes, pond detritus (when your pond fills up dig it out and lime it and add it to a mulch). Most fleshy green plants have carbon but also a fair bit of nitrogen and are available in large quantities: Japanese Bamboo, Jerusalem artichoke tops, daylilies, etc. There are many materials that could be used, so keep your eye out for sources in your neighbourhood.
Futons/Carpet,etc.: Here’s an idea try using old wool carpet for the sheet mulch layer (instead of newspaper and/or cardboard). It’s an even thickness, it won’t let the weeds through, and it will rot away in one to two years, just like newspaper or cardboard. Just be sure that there haven’t been any pesticides (flea powder, etc.) or fungicides sprayed on the carpet at any time, as these are not good for your plants. Also, consider old futon matresses for the mulch layer – they are perfect for those more difficult jobs such as bamboo thickets.
Newspaper and Corrugated Cardboard: These materials are easily found around your house, from your neighbours or from local businesses. Ask all your neighbours to save their newspapers for a week, or talk to your local appliance supply store to get the boxes that stoves, fridges and dishwashers are shipped in (these cover large areas very quickly).
Top dressing materials:
Top Dressing Materials: This is the only layer that might cost you a little money. The type of garden you have or are planning to create will dictate what kind of material you use for the aesthetic layer of the mulched plot. Whatever material you decide to use, be sure it is sourced locally and does the job – that is, it covers the newspaper well, doesn’t end up strewn about your yard, and is weed- and seed-free. Fraser Richmond Biocycle has a variety of mulch grades that look great in any garden, but you can also use straight straw, leaf mulch, or any other organic material that is attractive and easy to work with. Have a look around your community – use your imagination!
Or you can grow your own mulch:
Grow your own mulch:
Instead of sourcing mulch materials, you can grow your own. Consider the following:
Comfrey – High in nitrogen, potassium and a source of phosphorus, comfrey is easy to grow. Traditionally, it was grown around compost piles/bins both to capture nutrients and use as a compost starter (it adds enough nitrogen fast enough to get the compost working quickly).
Straw Substitutes – It can sometimes be difficult to source straw. Sword fern or pampas grass are attractive, weed- and seed-free, and easy to grow.
Fertility Patches – This a technique developed in England for increasing the organic content and nutrients of soil, especially nitrogen and phosphorus, and is perfect for sandy, low nutrient soils such as those we have on the Coast. The suggested planting is up to one third of the area under production be grown in alternating rows of comfrey and alfalfa for up to 6 years. Alfalfa does not grow that well in this area, so white clover and lupines might be a better option. Several harvests a year can then be mulched or incorporated into the soil of any areas that are in intensive annual vegetable production.
Classic Sheet Mulch Sequence
Basically a sheet mulch is like composting in layers directly on the ground. One general rule to keep in mind: each layer is usually 3 inches (10 cm) thick unless it is fresh chicken manure – then it is better to have at most 2 inches (5 cm).
Step 1: Plan the Plot
A great garden starts with good planning. Before planting any garden, it is important that you know your soil type (expecially pH levels – test kits can be bought quite inexpensively at most garden supply stores). The advantage to knowing your soil is that you will then know what plants are appropriate for the site, or, conversely, what remediation will be required for special- needs plants to thrive in your garden. Develop a plant list and a list of the materials you will require for your sheet mulch (see steps below) – and remember that you are creating a rich new growing medium for plants. In your plan, include fast-growing ground covers and plants that will keep the weeds down long after the sheet mulch has decomposed into the soil. Think through how you are going to keep weeds out for the long haul – the plants you pick should be to be easy to look after and require little water or special care.
Step 2: Collect the Materials
The size of the plot you will be creating will dictate how much material you will need to gather for your sheet mulching project. Generally, each layer will be about 3 inches (10 cm) thick. You will require the following materials:
- Dolomite lime and/or rock phosphate/bonemeal (depending on your soil type and planting plans)
- Nitrogenous materials
- Carbonous materials
- Lots of newspaper and/or corrugated cardboard
- Top dressing material
- The plants and/or large seeds you wish to set in your new plot
- Some friends to make the job go fast!
Step 3: Lay Out the Shape of the Area to Be Sheet Mulched
The best thing to use for this is an old garden hose, or something similarly “bendable” – this will allow you to create rounded corners for a more interesting garden design. Lay out the hose and try it in a variety of different positions on the ground so as to design the “perfect” layout for your new garden plot, perennial bed or berry patch, etc. Once you’ve decided on a shape…
Step 4: Water the Soil Until it Can Hold No More
Using a conventional sprinkler, water the soil in the area you want to sheet mulch for about 1 hour. If your soil is good and loamy (with a bit of clay), water it for one half hour more (1.5 hours total). The object is to put about 1 inch of water in the soil, as that is about as much as most soils can hold (assuming a high water table and no desert conditions!). Very dry places may need much more.
Step 5: Trample the Vegetation!
If the area to be sheet mulched contains growing vegetation, take a few minutes to trample it down, as flat as possible. Try not to cut the vegetation, as the technique works better if you don’t. This is the first layer of your sheet mulch. Your plot should now look like, well, a trampled mess!
Step 6: Lay Down a Carbonous Layer
Take weeds from other parts of the garden (or your neighbour’s gardens – they’ll love you!) and strew them about the space to be mulched. Then, lay down a layer of carbon material such as brown leaves, dried grass clippings, etc.
Step 7: The Soil Conditioner Layer
Sprinkle a few handfuls of dolomite or agricultural lime (organic but not labeled so) or rock phosphate/bone meal around your chosen sheet mulching site – your soil pH test results and planting plan will tell you what’s required. As a point of interest, most soils in the Lower Mainland are very acidic, resulting in weak calcium uptake (an important mineral for plant growth).
To Make Your Own Bone Meal – If your family and friends eat meat, save the bones for a few weeks in the freezer then dry them overnight in large batches in the oven. You can either store them in a dry place in this form until required, or you can crush them into bonemeal right away. To do this, place the bones in a strong cloth bag and crush them with the back of an ax or a sledgehammer. Then, come time to use bonemeal, spread them around – bonemeal contains nitrogen and calcium and raises the pH. Though this is a simple procedure, it’s often difficult to get enough bones to produce large volumes of bonemeal. Save this precious resource for use around your newly planted fruit trees and shrubs.
Step 8: The Nitrogen Layer
You now need a layer of high-nitrogen organic material to kick-start the decompostion process underneath the mulch. This layer can be full of weeds and weed seeds, as it will be blocked out by the newspaper/cardboard layer you will be putting on next. Typically, manure or grass clippings or cut comfrey work very well. Also, compost materials that don’t have enough carbon or have been kept too wet are good to use, as they are full of nitrogen. One word of advice – It is not a good idea to use fresh kitchen scraps due to their attractiveness to rats and mice, not to mention dogs, raccoons, bears, etc. (stick to materials that are not so tasty to our four-legged friends). This layer should be at least 3 inches thick (10 cm), but can be thicker if you have lots of material to dispose of.
Step 9: The Inocculation Layer
This layer is required to kick-start the decomposition process in your sheet mulch. Because some mulches are very thick, and have very poor soils under- neath which contain few decomposition organisms, it is a good idea to “inocculate” the sheet mulch with some additional “good bugs”. The best thing to use for this layer is compost – just a few handfuls scattered over the area to be mulched is perfect (don’t use more than this, as compost has better, more valuable uses). Compost both innoculates the mulch with beneficial bacteria and fungi, and introduces good insects, such as beetles and worms. If you don’t have access to compost, just use plain garden soil.
Step 10: The Sheet Mulch Layer
Now comes the critical component of sheet mulching – the sheet mulch itself. The best and most easily accessible materials to use are newspaper and/or corrugated cardboard, though you can also use old wool carpet or a variety of other materials (see page 11). You will need enough newspaper and/or corrugated cardboard to cover your desired space [i.e., 10 or so pages thick for light weeds in a veggie patch, 15 or 20 pages thick for a lawn, and 30 or more pages thick if it’s bindweed (morning glory)]. Open the newspapers up and lay them down in sections across the plot. Obviously, using large pieces of corrugated cardboard makes the job alot easier! While you’re covering the entire space to the edges, be careful to overlap the edges of each section by at least 4 inches (12 cm) so as to not allow the weeds to creep through, then water the whole thing again, very well. The newspapers and/or cardboard will need to be saturated to create a paper mache-type material (obviously, newspapers will work better for this than cardboard) to keep the weeds and unwanted plants down. There is no hard and fast recipe for sheet mulching – it’s mostly an artform developed by trial and error. The trick is to find out what works for you on your particular site, using the guidelines outlined here. The basic thing to remember is that the tougher the weed, the tougher the sheet mulch needs to be – the Coordinator of the Vancouver Permaculture Network has seen newspaper sheet mulches up to 1 inch thick! Here’s a tip – for the toughest jobs, use old carpet (see Page 11 for more informa- tion).
Step 11: Carbon Layer
This layer is not required, but it is preferred. The more layers a mulch has the better it becomes, increasing the variety of nutrients. Just remember that the carbon layer is above the sheet mulch layer – everything used here should be free of seeds (that includes hay, weeds, and grasses). If you use any materials containing seeds above the sheet mulch (newspaper/ cardboard) layer, you will end up with a very lush but weedy garden plot!
Step 12: The Aesthetic Layer
Once the mulch layer is good and wet, and you’ve added your carbon layer, it’s time to load on the aesthetic layer, which is the top layer designed to make the plot look attractive in your yard. You can use a variety of high-carbon materials, from straw to wood chips (note that there is a difference between wood chips and bark mulch – use the latter only as a very last resort as it has a tendency, because of it’s acidity, to kill plants fairly quickly, which isn’t so good if you are trying to grow a brand new garden). The type of material you choose will depend on your design, what materials are available, and how much money you want to spend, if any. Try hardwood chips (alder and maple), sword or bracken fern, or pampas grass as some alterna- tives. The most important thing is to try to locate local materials for your mulching project, which saves on fossil fuel use and air pollution. See Page 12 for ideas on other types of top- dressings. And remember – like the carbon layer in Step 11, any organic material used in the aesthetic layer must be weed and seed-free…
Step 13: The Plant Layer
And now you’re ready to plant – the same day you mulch is the same day the plants can go in the ground! Just pull back the top-dressing in the spots you wish to plant, use a garden knife to cut through the newspaper/corrugated cardboard mulch layer (cut an “x”), dig a hole large enough for the transplant or seed, fill it with a planting medium (garden soil from Fraser Richmond Biocycle (at the North Shore Transfer Station Chipping Yard – 924.9252) will work great, but so will other, weed-free garden soils), and pop in the plant or seed as you would in any garden. Then replace the mulch layers back around the plant and voila – the materials underneath the mulch will slowly decompose, helping to create balanced, healthy, biologically rich and diverse soils for your plants and garden. Planting in this way give the roots a choice to either grow down through the soil or out into the mulch. What could be better than that?
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