For permaculture, a major source of inspiration is old growth forests. Have you ever seen a forest with bare soil? A thick layer with dead leaves covers everything, and the earth beneath it feeds on humus that appears as leaves break down. All “pros” and no “cons” for mulch! Why is that we don’t see more of it in gardens?
Mulch in permaculture, how does it work?
It’s a technique that basically takes dead, dried plant material and layers it around the plants you’re trying to grow. Perfect for mulching, among others, are hay, straw, BRF (ramial chipped wood), dead leaves, flax, etc. Moist material also works, too: kitchen scraps, lawn trimmings…
To learn more, read:
What does mulch do your soil?
- Weed inhibitor. Those few weeds that will poke through anyways will be very easy to pull out. Weeding becomes a thing of the past!
- Enhances soil as it promotes biological activity. It indeed provides both food and shelter for beneficial insects. Bacteria that are already present in the soil break the soil down, it turns into humus that plants can feed off of. Soil structure is greatly enhanced: bacteria create loose spaces where air can enter. In the end, it feels like a loose, crumbly dough.
- Buffers temperature extremes: less heat in Summer, more warmth in Winter. Whenever it gets too hot or too cold, micro-organisms and insect life basically shut down and hibernate.
- Filters water during strong rains. Mulch breaks the fall of large, heavy drops. Even torrential rain only feels like a continuous drizzle to the top layers of soil when mulch protects it. Plants have more time to absorb the water since it doesn’t run off. On clay soil, mulch prevents rain from clogging pores shut: air can continue to circulate and no “crust” appears.
- Blocks out evaporation in Summer and keeps the soil from heating up too much. Traditionally, “a run of the hoe is worth two of the hose”… well, with mulch, you can even make it 5 runs of the hose!
- Keeps the soil from freezing in Winter and lets soil bacteria remain active even over the cold season.
Which mulch for permaculture? Advantages
Brown waste (dead leaves, BRF, horse manure):
These make for an excellent amendment. These are loaded with carbon, and mushrooms slowly dissolve them to produce soil humus. These fungus require moisture to go to work, so remember to throw a pail of water over them if it gets too dry.
Green waste (lawn trimmings, kitchen waste):
Directly stimulate soil bacteria. There’s lots of water content in them, and the amount of nitrogen they release is tremendous. Quickly converted to better soil.
- Lawn trimmings:
Apply only in very thin layers if using fresh trimmings. Sprinkle it lightly, since thick layers will clump up and rot. Rotting lawn trimmings produce too much heat and don’t match the needs of soil organisms.
Read also: How to use lawn trimmings in the compost
- Kitchen scraps:
Spread these out as a single layer, and then cover it with another type of mulch to lock moisture in and keep it beautiful…
Straw and hay:
- Straw: contains very high levels of carbon, and, as a result, requires time to break down completely. Use it as a long-term ground cover (for the entire Summer or Winter for instance). Slip kitchen scraps and peelings under it, they’ll disappear in a jiffy!
- Hay: more or less 50% nitrogen and 50% carbon. Hay is thus very balanced, and will both protect the soil for a long time while slowly releasing nitrogen.
How to use mulch for permaculture
Don’t bury plants under the mulch. Specifically, make sure the root collar of the plant remains free, this is where the stem meets ground level. How thick to layer the mulch depends on how fast it breaks down and how long it’s expected to stay:
- For perennial plants:
Plan for a thick layer of brown mulch, spread all around the stem or trunk. It should last a full year. Spread it in Fall, when the soil gets a lot of natural rainwater.
- For annual crops:
Adjust the thickness to the size of the plant. Remember to mulch again during the growing season.
Worm, Shakeitha Stone by U.S. Department of Agriculture under Public Domain
Spreading mulch for permaculture by U.S. Department of Agriculture under Public Domain
Mulch prepared from shredded wood by North Carolina Department of Transportation under © CC BY 2.0