Sheet Mulching

Sheet mulching is probably the best way to build organic matter and microorganisms into the soil. By composting in place, you are allowing all the by-products of composting to actually be utilized by the plants you are trying to benefit.

Every time you turn a compost pile or dig into your compost to bring it to the garden, you are killing millions of organisms simply by exposing them to air and sunshine. Colonies of fungi and bacteria are busily creating a network of communication and chemistry, all beneficial to our plants. So composting in place, also called sheet composting or sheet mulching, is preferred.

You can use various techniques for sheet mulching. But some basic concepts should be kept in mind: just as with building a compost pile, you want about 2/3 “browns,” or carbon sources, to 1/3 “greens,” or nitrogen sources (manure being a nitrogen source, though not  green in color).  Be sure to water all the layers well.

Sheet mulching can be as easy as placing down layers of cardboard followed by wood chips on top or as extravagant as a 16-layer cake.  

Here is a list of some good materials for sheet mulching.

"Greens," or nitrogen-rich materials:

• Grass clippings

• Compost

• Manure

• Fresh weeds (without seeds)

• Waste produce from the kitchen

• Blood meal

• Seaweed

• Coffee grounds                                        

And "browns" that are carbon-rich materials:

• Cardboard

• Newspaper

• Straw

• Dried leaves

• Wood shavings or chips

• Bark

You want to alternate the greens and the browns, and you also want to be sure to layer in some compost to introduce micro- and macro-organisms into the pile.  

​Finish up your sheet mulching project with some wood chips to encourage fungal microorganisms, increasing diversity and resilience. Watch these slides to see the process:

1: Set out your plants

Take some time to understand how big your plants are going to get and set them in place in their pots to visualize the arrangement. Create a map so you can recreate this arrangement once your sheet mulching is complete.

2: First layer

You can create a line to be the edge of the bed with a hose. If your soil is compacted open up the soil and loosen it slightly with a garden fork or spade over the entire area. Sprinkle some compost over the ground or sod for your first layer. It's best if this is homemade compost and has some worms in it.

3: Spreading your minerals

Next you can add your bonemeal or rock phosphate, greensand, and wood ash..

4: Lay wet cardboard

After you have the ground well watered, layer on your wet cardboard overlapping a few inches.

5: Water again

You will want all the material to be moist so the beneficial microorganisms are happy.

6: Bring on organic matter

Add leaves, weeds, any green plant material, etc. Water well.

7: Manure is next

It is ideal to have manure from a local source. Watering after each layer!

8: Top layer

If you have plenty of material you can repeat some layers, always alternating your greens and browns. The final layer in this sheet mulching project was salt marsh hay. Some people use wood chips or any carbon rich material.

9: Planting

Planting through the mulch is easy. Push the layers to the side in a small circular area and use your hands or a trowel to make a hole through the cardboard and in the underlying soil.

10: Planting

Place your plant in the hole and fill the soil back around the roots. Replace the layers back around the root ball.