If you ask a representative sample of gardeners what they least enjoy doing in the garden, you’re likely to get the same answer from most of them: weeding. In my own experience as a low-maintenance landscape designer and professional gardener, I can tell you that it doesn’t have to be this way.
Gardening shouldn’t be about slogging away day after day trying to kill the multi headed-hydras of the plant world. Weeding is by and large unnecessary if your garden is designed well, and although getting to the point of a nearly weed-free garden is an art and science in itself, sheet mulching for weed control is a good place to start.
Sheet mulching, or lasagna gardening as it’s also called, is a technique for smothering and permanently killing weeds in existing garden beds, building soil fertility and organic matter, and starting new garden beds. The basic idea is to create rich soil on the spot through compost building using alternating layers of carbon and nitrogen rich materials (see below). Now that you know the basics, let’s get down to the steps involved:
Step 1: Collect materials
To increase decomposition speed and create balanced compost during a regular composting process, it is recommended that you aim for a carbon-to-nitrogen ratio of about 30 to 1 in the materials used. When sheet mulching, it’s fine if that ratio is a little off, but it’s still a good idea to shoot for a ratio somewhere between 30 to 1 and 100 to 1.
Four to eight yards of mulch will be needed for about 100 to 200 feet square, which is about 6 to 10 bales of very rotten hay or seedless straw, for example. Ideas for materials: Nitrogen-rich materials include things like kitchen scraps and manure, while carbon rich materials include things like leaves, sawdust, cardboard, small branches and wood chips. A good base layer of cardboard can often be acquired from farm supply, appliance or bike stores.
Step 2: Water the soil
The evening or day before your sheet mulching project, water the soil at the site if the ground is not already moist. This helps kickstart microorganisms and will make it easier to ensure the bottom of your pile starts off moist.
Step 3: Cut existing vegetation
Simply cut the area to make putting down your layers easier and leave the debris where it is.
Step 4: Add soil amendments
To create a rich soil add organic fertilizers like greensand, seaweed powder, rock dust and other amendments directly to the existing soil. You might also consider doing a pH test and amending based on pH. For example, overly acidic soil can be amended with lime while overly alkaline soil can be amended with sulfur or gypsum.
Step 5: Break up compaction
Use a spading fork or broad fork to break up and loosen the soil and work in your amendments. This brings oxygen into the soil and helps prepare it for better water and root infiltration. Avoid mixing soil layers, which is bad for the soil ecology.
Step 6: First layer
The first layer is a nitrogen rich layer such as compost, composted manure or livestock bedding (or non-composted things like manure or restaurant kitchen scraps if you’ll be giving it a few months before using the bed). Moisten this first layer, but do not make it soggy.
Step 7: Smothering layer
The second layer is your smothering layer, usually a layer of cardboard or newspaper. I recommend cardboard, which is fairly easy to find and creates a thicker layer more easily. The bigger the pieces you can get, the better. The smothering layer pieces should overlap by at least 6 inches, if not a full foot, and it should be 1/8 of an inch thick. Water the material to keep it from blowing away and avoid walking on it so it doesn’t tear.
Step 8: Nitrogen layer 2
Self-explanatory: another layer similar to the first.
Step 9: Bulk carbon
Now it’s time to add a thick layer (8 to 12 inches) of carbon material such as weed-free straw or rotted hay. If you only have potentially seedy mulch, you can still use it, but in that case it’s important to add further layers on top to ensure the seeds rot rather than germinate. You can also sprinkle in seaweed powder or other nitrogen-rich material here, and water every few inches to dampen.
Step 10: Repeat
Continue adding layers as deep as you like.
Step 11: Compost layer
When you get to your second last layer, it’s time to add at least a couple of inches of compost, or several inches of compostable materials if you will be letting it compost on the spot for a few months prior to planting. This will be your seeding or planting medium.
Step 12: Final layer
Finish it off with at least 3-6 inches of mulch that is completely weed- (and root-) free. Wood chips are great for this layer if possible since they last longer before decomposing. Leaves, rotted hay or seedless straw also will work.
Step 13: Plant
To plant seeds, separate the mulch aside into your desired planting patterns and plant away, leaving the mulch where you don’t plant. Sprinkle a small amount of mulch on top of the seed areas to prevent evaporation and increase seed germination. For plants, make sure to plant into the soil, and tuck the mulch right up to the plant once planted.
That’s all there is to creating low-maintenance, nutrient-rich, moisture-retaining garden beds. It might be a little more work to start, but it is more than worth it once you experience the freedom of a (mostly) weed-free garden full of healthy, disease-free plants. Even the few weeds that do manage to poke their way through or germinate among your plants will be easy to pull since the soil will be loose and moist (as long as you do double-reach, no-walk beds to avoid compaction). At this point, all you have to do is add more mulch each year, or gradually replace it with living mulches to maintain an even lower maintenance, weed-free garden.
Do you have any experience with sheet mulching or other time-saving methods for new garden bed creation? Please share your own experience and comments