Three Easy Sheet Mulching Methods

Freshly sheet mulched area. The mulch will settle at soil level after decomposition.

Sheet mulching is a gardening technique that suppresses weeds and builds fertile soil. In sheet mulching thick layers of organic matter are placed on the ground lasagna style. These layers are then left to decompose ultimately creating a rich planting medium (compost) that is terrific for vegetable gardens and ornamental planting beds.

The advantage of sheet mulching over composting in a bin is that the finished compost does not have to be hauled to the actual planting bed. It is created right on top the planting bed. The process can take three to six months so it is best to plan ahead and sheet mulch the season before you want to install your plants. However, it is possible to install some plants right after you sheet-mulch by punching a hole through the sheet mulch for each plant and popping them in.

Sheet mulching is effective at suppressing weeds because it is so thick – as much as 12 inches – and because one of the bottom layers has no holes in it for air and light to sneak in. The weeds and anything else underneath are snuffed out. You can even sheet mulch right over the top of sod. There is no need to remove the lawn ahead of time.

I’ve taught many people how to sheet mulch in the permaculture workshops I used to lead at Kenwood Permaculture. My goal in this article is to describe various sheet mulching options. Each one is progressively more complex.  But they are all easy and fun, especially with a group of people at a sheet-mulching party.

Materials:

Don’t worry about the length of this list. You can successfully sheet mulch with just three of these items.

a. Sheet Mulch*. The sheet mulch layer is a solid layer of overlapping cardboard pieces (remove tape – it doesn’t decompose), newspaper (¼” thick -no glossies), old 100% cotton sheets or blankets, or wool carpet. No synthetics.

The most commonly used sheet mulch material is cardboard. Try to find plenty of big pieces from house-hold appliances or computers. They cover a lot more square footage than a shoe box.

b.Soil Amendments. This depends on your soil needs. Use gypsum for clay soil or compacted soil. Use bone meal, blood meal, or cottonseed meal to increase nitrogen. Use lime if your soil is too acid. Green sand, rock dust and kelp have trace minerals. Elemental sulfur increases soil acidity.

c. Bulk organic mulch*. Straw, weed free garden waste, garden trimmings, leaves, bark, stable straw.

Straw from bales is easy to work. It often peels off in nice layers and is compacted so it doesn’t blow around in the wind. Straw bales cost more than other bulk mulches obtained from your own backyard.  Other bulk mulches (yard waste, trimmings, leaves tend to be courser than straw and can have a lot of air pockets when you put them down. If you are aiming for a 6” thickness they will settle out much lower – maybe 3-4” so you have to compensate by adding more. Don’t use hay. It has seeds in it

d. Compost.

e. Manure. Goat, sheep, horse, chicken, steer. See if you can find some for free at local stables. Don’t use dog or cat feces.

f. Top mulch layer. Shredded bark, leaves, straw. This is basically the same material as the bulk mulch layer.

g. Water*. You’ll need a fair bit of water. But a proper compost pile is moist – not soggy. You might be concerned about adding water at every level if you live in an arid or semi-arid location. The trade-off is that you are building rich, organic soil that will hold  moisture more effectively and will produce beautiful crops and ornamental plants.

* – Required materials.

Tools.

1) Gloves
2) Scissors to cut twine from straw bales
3) Tarps to hold your compost, manure and other amendments close to the sheet mulch area
4) Large buckets, transfer shovels, pitchforks to move amendments around
5) Hose(s) with sprayer(s)

Planning:

1) Ideally you’ll sheet mulch the season before you plan to actually use the planting bed. In regions with a distinct rainy season it is best to sheet mulch right before the rains as more consistent moisture assists decomposition.

2) Calculate the square footage of the area you will sheet mulch to determine how much material you will need. It isn’t much fun to get geared up for a sheet mulching project and then run out of cardboard half-way through the job. For a 23’ by 7’ planting bed you’ll need (23 x 7 = 161) 161 square feet.

3) Choose the sheet mulching method you will use. Based on this calculate the cubic footage of bulk mulch, compost, manure or other amendments you will need. An online calculator for cubic feet is http://www.gardeners.com/Soil-Calculator/7558,default,pg.html. Eight inches of bulk mulch on top of that 161 square foot area requires about 4 cubic yards of mulch. First, convert to inches – (23’x7’) = (276” x 84”) x 8”. Then use the online calculator which gives you 108 cubic feet or 3.975 cubic yards of mulch.

4) Gather all your materials and tools ahead of time. It is easiest if you have them all staged near the sheet mulch area.

Three Easy Sheet Mulching Methods

I call these approaches: a) simple; b) advanced; and, c) super. The simple approach is faster and cheaper. The more complex approaches take more time, materials and money but they potentiate long-term soil fertility by aiming for a balanced carbon to nitrogen ratio that is ideal for composting.

Option 1) Simple SHEET MULCHING

1) Slash down tall weeds. Leave the weeds on the ground.

2) Water the area to be sheet mulched.

3) Put down a good layer of cardboard (or newspaper ¼” thick). Make sure there are no gaps between the cardboard. The pieces must overlap. This is the “sheet” layer. Water generously.

4) Put down 6” of straw. Water generously.

5) Wait 3-6 months for it to decompose.

Option 2) Advanced SHEET MULCHING

1) Slash down weeds. Leave the weeds on the ground.

2) Water the area to be sheet mulched.

3) Add compost and/or manure. This layer can be 1/4″ – 3” thick. Water generously.

4) Put down a layer of cardboard (or newspaper ¼” thick). Water generously.

5) Add more compost and/or manure – 1/4″ – 3” thick. Water generously.

6) Put down 6-12” straw or mulch. Water again.

7) Wait 3-6 months for it to decompose.

Option 3) Super SHEET MULCHING

1) Water the area thoroughly beforehand.

2) Slash down tall weeds. No need to pull them out.

3) Add soil amendments as needed. Sprinkle them around generously. Water.

4) If your soil is compacted, break it up a little with a pitch fork or spade.

5) Add a 1/2″-1″ of manure, blood meal, fish meal, cottonseed meal, grass, and/or kitchen scraps. Add water.

6) Lay down the cardboard or ¼” newspaper. Remember that all pieces should overlap.

7) Add another 1/2″ – 1″ of manure, blood meal, fish meal, cottonseed meal, grass, and/or kitchen scraps. Water generously.

8) Bulk organic mulch – (straw, yard waste, etc) 6-12″. Water generously.

9) Add 2” of compost. And more water. Supplement with soil/manure if you don’t have enough compost.

10) Add a 2” Finish layer of mulch, straw, or shredded bark(looks nicest if it is in a visible area) Add a final dose of water.

11) Wait 3-6 months for it to decompose.


 


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17 Responses to Three Easy Sheet Mulching Methods

  1. Pingback: The Fall « kentgarden.org

  2. Onyekachukwu says:

    I have done this with great success. I used whole neaspwpers and made sure they are overlapped. Don’t worry about wetting them though unless it is extremely windy. A couple of sheets will break down pretty quickly so I think the extra thickness is what does the trick. I used this around shrubs and then applied 5″ of wood chip for shrub beds. I left an area of 8″ x 8″ around each shrub to allow for water penetration. No weeds from underneath ever, it has now been 5 years. You will always get wind borne weed seeds sprouting in the top mulch but I didn’t even weed the seasonal grasses before I laid the mulch down. No plant can grow without light. My newsagent will give you the neaspwpers (yesterdays that no one bought, saves him paying to have them recycled), I collect them over a period and it gives me great quantities to use over big areas.I wouldn’t use this method in flower beds or perennial borders it would take the paper to long to breakdown. Even though the news paper is now completely broken down I’m only getting weeds in the top mulch, the seed cycle for the weeds underneath seems to have been broken. Hope this helps.References :

  3. Dawn Trautwein says:

    I would love to try this method over a half-acre plot that abuts the woods, however I do not currently compost so Im worried about getting my hands on “kitchen compost”. My neighbor has horses so I have plenty of manure and stable straw. Can I substitute manure and straw for those two layers?

  4. johanna says:

    one thing to be aware of: straw and hay are sprayed with some very toxic stuff these days that are ”weed” suppressors–ie they will *also* suppress vegetables and other desirable things, except grass species for hay. examples of common sprays on straw, hay or alfalfa are: Roundup, Graze-On, 2,4-D, Express , Quadris, Stratego, Headline, Axial XL, and so on… they are pretty toxic.
    these compounds also are found in animals that are grazed on these pastures, even after the ”60 day wait” period.
    so while straw etc has worked amazingly well for me as mulch, it’s a good idea to be careful where you get your manure and mulch from (get organic at least!), because it can also make a great planting go bad 🙁

  5. johanna says:

    i meant to say ”these compounds are also found in THE MANURE OF animals grazed on these pastures…
    thanks 🙂

  6. Kim wilson says:

    So excited to try this. However, I’m late this year. What are the suggestions for getting started in a smaller area with plans to expand into next spring?

    • Karen says:

      Kim, There is no problem with sheet mulching a small area first and then expanding to another area later. Just follow the sheet mulching instructions for each area when you get to it. Good luck!

  7. Matt says:

    Hi, this is a great resource. I am working on a large yard that has no grass already. I plant to super sheet mulch and I have a few questions.

    The top layer can be bark mulch, is that correct? Once I am done sheet mulching the yard, can I plant certain areas before the 3-6 months of decomposition? If so, what’s the best way to plant the materials?

    • Karen says:

      Hi Matt,

      Yes, The top layer can be bark.

      If you plant in the sheet mulch before it decomposes cut or dig a planting hole in the sheet mulch and install the plant in existing soil. The planting hole should be twice as wide as the root ball. You can amend the hole with 25-50% compost/potting soil if it is a veggie, fruit tree or any other plant requiring richer soil. Otherwise you can simply back fill the hole with native soil. Sometimes this is tricky if your sheet mulch is really thick and your plant is tiny. Keep an eye on the new plant so it doesn’t get buried by the sheet mulch layers folding in on it.

  8. Pam says:

    Have you acts used chicken manure? I’ve read that typically it is “hot” and high in salts and care should be used when using it

  9. Evelyn Hurley says:

    I live in Northern California – not expecting any rain until fall – if I sheet mulch now should I plan to water the area periodically? and if so how often?

    • Karen says:

      Hello Evelyn, You don’t have to water your sheet mulch area over the summer. However, keeping the sheet mulch moist will speed up decomposition. If that is what you want try watering it once a month.

  10. Linda says:

    I’m in the high desert, Western Slope of CO, a good elevation, just over 5,000 ft. I started various veges inside but when I moved them to the long ago used garden area they could not grow bigger, (in spite of my surrounding them with the organic potting mix) while the ones I gave my neighbors are doing great. Squashes, mostly. I had spread some chicken manure and straw last fall but evidently it was not enough. I cannot buy anything (the seeds are free at our seed exchange at the library) the clean cardboard near me is free. I am wondering about the ink in the newsprint, there is plenty of that available but am concerned as I need to grow food. What do you know about that for veges? I have some compost, one person doesn’t generate a lot. Perhaps I should start with a smaller area. I appreciate finding this site, thanks for any help.

    • Karen says:

      Linda, Most newspapers use soy based ink and the consensus seams to be that this ink is safe for composting. I do recommend you start small with sheet mulching. Gathering the materials for a large area is a lot of work. Plus, you can more easily observe how your sheet mulch breaks down and adjust the recipe as you move on to the next area.

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