Want to reduce weeds in your garden, build better soil, and water less? Sheet mulching is an elegantly simple way to achieve all three goals at once!
Sheet mulching involves applying your choice of organic mulch materials (we love wood chips) on top of a layer of cardboard or thick layers of newspaper. This is a great way to control weeds in the pathways between your garden beds, and you can also use this method to smother out grass and weeds for a future garden space. (Keep in mind that you will want to plan ahead and lay down your sheet mulch the year before you will be planting in the new garden space to give everything time to break down and feed the soil.)
Both the weeds and the cardboard will decompose under the mulch over time, encouraging earthworm activity and enriching the soil underneath. The cardboard will also help trap moisture, preventing your soil from drying out as quickly and reducing the need for watering.
Here are 3 simple steps to using sheet mulching in your garden:
1. Get the right materials. You’ll need cardboard, mulch and/or organic matter, and manure (but that’s optional). At a minimum, you just need enough cardboard to cover the earth and enough mulch to cover the cardboard. From the there the sky is the limit: You can pile up as many layers of manure and organic matter as you want. Woodchips, straw, leaves, crop wastes, and animal bedding are all examples of organic matter…
Recycling centers are a great source of cardboard. Unless you are sheet mulching a tiny area, try to grab the biggest sheets of cardboard you can find, such as boxes from bicycles and kitchen appliances, to make things easier. Avoid cardboard with glossy color print, as the ink may not be biodegradable. Some people use a thick layer of newspaper instead of cardboard, which is efficient only for sheet mulching small spaces.
2. Lay down the cardboard. Unless the soil where you’re planning to sheet mulch is already very moist, set up a sprinkler and soak it before laying down the cardboard. Remove all the tape from the cardboard (it’s not biodegradable) and lay the cardboard over the soil/weeds working from one end of the space to the other.
It’s critical to overlap the pieces of cardboard by at least six inches to prevent the more tenacious weeds from weaseling through the gaps to the surface, where they will quickly become re-established in the rich soil you’ve made for them…
3. Add organic matter. If you’re just adding mulch, spread what you have in an even layer at least 2 inches thick on top of the cardboard and call it done. If you’re also using manure to prepare a future garden area, spread it in two-inch layers alternated with a one-inch layer of organic material between each one, finishing with a final layer of mulch on top. Another option is to simply cover the cardboard with finished compost and then cover the compost with a protective layer of mulch.