Lasagne bed: build it in autumn and know its limits

Do you want a fertile bed without buying potting mix? The lasagne bed makes it possible. Layers of brown and green materials compost in place, under your future vegetables. Build it this autumn, with the leaves that are falling. By spring, it will have lost about half its height and it will be ready to plant. Its two limits are rarely mentioned. It settles and it dries out fast in summer.

What is a lasagne bed?

The lasagne bed is a compost you never turn, built right where you are going to grow. American extension services call it "sheet mulch composting" or "lasagna gardening". It is cold composting. The material breaks down slowly, without heating up like a pile you turn.

In June 2024, I built a raised box this way for the "Alerte radin" (cheapskate alert) video, the most watched of the series. Wood at the bottom, then cut grass and straw in alternation. To finish, 25 cm of potting mix or garden soil. All for not even €2. I planted garlic in it in September, harvested in mid-June 2025.

Many permaculturists use the lasagne, but it does not come from permaculture. It is a technique, not a design method. The overview Six methods put to the test places it among the others.

The layers and their proportions

Two university services give similar recipes. They differ on proportions.

Sources: Oregon State University Extension for the layers and thicknesses, Ohio State University Extension for the height and the top.

Oregon State advises brown and green layers of about equal thickness. Ohio State aims for two parts brown material to one part green. In both cases, you alternate instead of stacking a single material. For my part, I let the cut grass dry for a day or two, so it is not too wet.

These two sheets also give a few precautions. Sawdust is very rich in carbon. Put it in thinner layers, well watered. No meat, oil or dairy, which attract animals. On a lawn, turn over the clumps of grass before stacking. As they break down, they feed the bed. If your plot has horsetail, avoid corrugated cardboard. It gets into its flutes.

Why build it in autumn

In autumn, dead leaves cost nothing. And the bed needs time. Oregon State sums it up like this. A bed finished in autumn is ready to plant in spring. A bed built in June, like mine, can also carry vegetables right away. Then plant in soil or compost laid on top.

To plant in a fresh bed, Oregon State gives the way to do it. Dig a hole twice as big as the rootball and fill it with compost. Decomposing material releases acids that can damage young roots. For a sowing, sow in 2 to 5 cm of sieved compost laid on top.

First limit: it settles

A 60 cm bed in November may therefore be only 30 by September. No cause for worry, the compost is being made. But if you built a raised box, plan to top it up every autumn. In mine, I regularly put kitchen scraps on the surface. That is called surface composting. It saves managing a big pile next to it.

Second limit: it dries out fast in summer

The RHS, the British horticultural society, says it for all raised beds. They dry out faster than soil at garden level. According to it, raising is only really necessary where the soil is waterlogged. A lasagne bed combines both faults. It is raised. And its airy materials let water drain away.

Under the June 2024 video, a viewer pointed it out. On dry soil, the water in the bed goes down and away. You then have to water a lot to keep it moist. He was right in principle, even though nobody has put a figure on the difference.

The other objections

Under the same video, another viewer noted that burying organic matter slows its breakdown, which needs air. That is partly true. A cold compost breaks down more slowly than a turned pile. So you build it in autumn to plant in spring.

You also read that the bed attracts rodents. That is plausible in a pile of straw and peelings, but we found no data. According to Oregon State, the brown layer laid over each green layer at least limits smells.

The yield of a lasagne

We found no trial that compares the yield of a lasagne bed with that of a conventional bed. The closest cousin is Charles Dowding's trial, in England. He compares two beds of 7.5 m². On one, the compost is laid on the surface. On the other, it is dug in. In 13 years, the no-dig bed gave 1,374.77 kg, against 1,218.80 kg for the other. Dowding says it himself. A single pair of beds gives indications, not proof.

So the lasagne does the job of a compost in place. It turns leaves and clippings into soil, without digging. It does not make vegetables grow faster than good compost laid on a bed.

In spring, the app gives you the planting window of each vegetable for your region. See your dates.

To go further, read Turning a lawn into a vegetable garden without digging. For buried wood, Mound growing and hügelkultur. Dowding's trial is detailed in To dig or not to dig.

Photo: Natureln, Wikimedia Commons, licence CC BY-SA 4.0