Mulch, step by step
Interactive lesson: straw, hay, leaves and cardboard — which mulch for which crop, when to put it down, a no-dig bed and how to solve the problems.
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The whole lesson as text
1. What mulch does
In a forest nobody hoes or waters, yet the soil is loose, moist and full of life.
- A forest is never bare — Mulch is a layer of organic material on the soil surface. For most crops 5–10 cm is enough.
- Less water — Sun and wind don't dry the surface, so a mulched bed needs roughly half the watering in summer. Bare soil forms a crust and erodes.
- Fewer weeds, less heat — Weed seed gets no light. The soil is cooler in summer and freezes less in winter, and in the sun the difference at the surface can be up to 10 °C.
- Food and clean fruit — Worms pull the mulch into the soil, and humus builds up over the years. Tomatoes, squash and strawberries don't lie in mud, so less of the fruit rots.
Why: The secret is the cover of leaves that falls every autumn and slowly rots. Mulch is the same principle in the garden: a layer of organic material on the surface that keeps water in, smothers weeds and feeds the worms from above.
- On sandy soil and in dry areas, mulch is the biggest water saving you can make for a day's work.
- With drip lines under the mulch, the water goes straight to the roots and none evaporates.
2. Materials: what goes where
Every material has its own depth, lifespan and place in the garden.
- Straw and hay — Straw goes on 10–15 cm deep, settles to 5–8 cm and lasts one season. Hay carries grass and weed seed: old, rain-washed hay is best.
- Grass and leaves — Grass clippings go on wilted, 2–3 cm deep, and add nitrogen. Shred leaves, because whole ones mat together; walnut leaves don't go on vegetables.
- Wood chip and cardboard — Wood chip lasts 2–3 years and is best for fruit trees, soft fruit and paths. Soak plain cardboard with no tape and always cover it with other mulch.
- On top, not dug in — Wood chip, bark, sawdust and straw are safe as mulch on the surface. Mixed into the soil they take nitrogen, and vegetables turn yellow for several weeks.
Why: The micro-organisms that break down straw, sawdust and wood chip need nitrogen. On the surface they take it only from the thin contact layer with the soil; mixed into the soil, they take it from the whole root zone.
- Straw and hay from fields sprayed with herbicides (aminopyralid, clopyralid, picloram) curl tomatoes, potatoes, beans and peas. Ask where it came from and do the bean test.
- A 2–3 cm layer of compost feeds, but smothers weeds poorly. Sawdust only from untreated wood.
3. When and how much · Locked
When you buy the Mulch module, you get the PDF to download and print and permanent access to this interactive lesson: all 6 chapters, 25 steps.
4. The no-dig bed · Locked
When you buy the Mulch module, you get the PDF to download and print and permanent access to this interactive lesson: all 6 chapters, 25 steps.
5. Fruit trees, soft fruit and paths · Locked
When you buy the Mulch module, you get the PDF to download and print and permanent access to this interactive lesson: all 6 chapters, 25 steps.
6. Problems and solutions · Locked
When you buy the Mulch module, you get the PDF to download and print and permanent access to this interactive lesson: all 6 chapters, 25 steps.