Sheet Mulching 101

– the What, the Why and the How

By Kim Dostaler, Employee-Owner
Close-up of honeybee on a flower

One of the quickest ways to create thriving healthy soil for a garden and to reduce the amount of lawn you have is to sheet mulch. Sheet mulching (sometimes called lasagna mulching) is a process of creating a new garden bed or planting zone over an area of grass by layering on “sheets” of organic matter. The process serves several functions: it suppresses grass and weeds, it adds a lot of organic matter all at once, it will serve to hold more water, over time it will break up the compacted soil underneath it, and it will save you time, money and fossil fuels by reducing the amount of lawn you need to mow. Not to mention it’s a fun fall or springtime project that you can involve the whole family in. You can use this method to build perennial beds as wells as annual beds.

Make sure you do some preliminary work before starting:

Pulling soil cores to send in for soil analysis.

Get your soil analyzed. You will want to add any mineral amendments your soil might need before you start this process. Usually you can get your soil tested at a near by university or agricultural program. If you don’t have time to do this, just add Gardener’s Greensand for a quick mineral boost. A very large problem with food today, even organic, is its lack of minerals. We’ve tilled and grown and tilled and grown in fields for so long that most of the soil in this country has become mineral depleted. We forget that if we grow food, nutrients and minerals are being taken up by plants, and it’s our responsibility to replenish those things.

Gather your materials:

Depending on the size of the area you want to cover, you’ll need a decent amount of supplies.

  • Soil Amendments – Green sand, and any other mineral amendments your soil needs
  • Nitrogen rich material – blood meal, fresh manure, Super Hot Compost Starter, fresh food scraps, diluted clean urine
  • Cardboard or newspaper. You’ll want enough to overlap the pieces by about 6”. If you are using newspaper, you’ll want it ½”-1” thick
  • 8”-10” layer of brown material – dried grass (without seed heads), old leaves, straw
  • Compost or quality top soil, enough to cover the area with 2”-3”
  • Mulch- more straw, leaves, Gardener’s Mulch Block
Sheet much layers

The process:

1. Make sure the area to be mulch is decently wet before you start. Rain the night before is good, or water it thoroughly before starting.

2. Chop down any existing vegetation and leave in place.

3. Aerate the area with a ground breaking tool or pitch/broadfork.

4. Amend your soil with the green sand or other mineral amendments. Broadcast over the whole area.

5. Lay down a material high in nitrogen – blood meal, manure, even urine diluted with water. Wet this layer down.

Thoroughly wet the cardboard to speed up decomposition.

6. Weed suppression step! This definitely takes the longest of all the steps. You need to thoroughly wet your cardboard or newspaper as you lay it. With cardboard this will take a while. Do both sides to really wet the cardboard through. Wetting it will help speed up decomposition. Now, lay the cardboard or newspaper down to form the square footage of your planting area. You’ll want to overlap by about 6” to make sure no grass or weeds can poke through.

7. Lay down another layer of material high in nitrogen on top of the cardboard. This will entice the worms and other soil good guys to eat through the cardboard and come up to join the party in your soil. This is also where you might add fresh food scraps. Wet this down.

Sheet much layers

8. Now you will be laying the bulk of your organic material on top of the cardboard. What you are looking for here is dead brown matter. Old dead grasses, strawbale or leaves, are generally what I have seen used. You will want to layer this material on 8-10” thick, and then wet it down to the consistency of a sponge.

9. Here comes a point of difference, depending on whether you got it together enough to do this process in the fall or if you are doing it in the spring. If you managed to get to it in the fall, you are done for now! Let all that goodness sit over the winter and break down. Come spring you should add a layer 2-3” thick of compost down and plant away. You could also lay the compost down now if you are worried about your brown material blowing away.

Adding compost in sheet mulch processAdding 2-3 inches of compost

10. If you are a procrastinator like me, you probably didn’t get to the process in fall. No fear, you can still plant into these beds, by making some adjustments when you plant. First, layer on the compost on 2-3” thick.

  • If you are sowing seeds, before you sow, stick a long knife down into your sheet mulch and cut some holes in the cardboard for roots to go through (if they are particularly deep rooted plants).
  • If you are planting starts, do the same as above, cutting an X in the cardboard under your seedling. Additionally, make a little hole in your sheet mulch and fill it with compost, and plant your seedling into this filled in hole.
Sheet much layers

11. Now, whether you sheet mulched in the fall or spring, the final step is the same. You want to mulch on top of your compost and around your plants. This is a crucial step and will save you work down the road. Mulch keeps your soil cool and moist, helping it hold water longer, which means less frequent watering for you. It also suppresses weeds, and thirdly it will eventually break down and add even more organic matter to your soil. Good mulch choices are straw, old leaves, or Gardener’s Mulch Bricks. If you are making a perennial bed, you could choose to plant a living ground cover, like clover. Clover is a great choice as it adds nitrogen to the soil (ie “fixes nitrogen”), and you can chop and drop it several times a year to add even more organic matter to your beds.

From this point forward instead of rototilling every year, just add an inch or two of compost or something like chicken manure (pull back your mulch first if you still have some left over on the beds). Over several years you will build up a thick, rich layer of gorgeous soil that your plants will thrive in.

Sheet mulching accomplishes many goals in one process – suppressing weeds, adding organic matter, bringing good soil life to your garden beds. It does this by mimicking the way mother nature would accomplish the same thing (a forest with leaf cover), only speeded up and managed by you!

Last updated: 12/14/2022