Mulch, Biomass, Mulchers

Today I want to talk about mulch.

To most people that sounds like a rather boring and mundane topic, however it is one of the most foundational subjects when it comes to permaculture and any sort of regenerative gardening!

If you have a full food forest, a garden plot, or even small planters on a balcony this will be very helpful information! Let’s dig in (no pun intended, but I’m running out of way to say that).

Mulch

What is mulch?

Mulch simply put is any organic matter that covers soil.

Landscapers often refer to pebbles or gravel as “rock mulch”. There is definitely a place for rocks in the garden, however the role that organic mulch plays is distinct enough from the roles of stones that I like to consider them separate tools.

In nature, mulch is absolutely everywhere. In forests you’ll see carpets of leaves or conifer needles. In meadows and prairies, you’ll find layers of dead grasses, and even in sparse rocky areas you’ll find lichens and hardy pioneer species acting as living mulches (more on that later).

How it works

Mulch has a few very important roles to play in a natural ecosystem: water retention, nutrient accumulation, weed suppression, and soil temperature regulation.

When soil is bare, water evaporates very quickly and loses nutrients. When soil is covered, however, it traps that water in like a sponge but can still breathe!

As mulch breaks down, the nutrients from the composted material actually build soil health and encourage essential microbial growth.

Examples

I have tried a handful of mulches, and here are my brief thoughts on each:

• Woodchips: By far my favorite mulch. I get this in huge loads for free from local tree trimmers that I trust. It’s abundant for me, I like how well it holds water and insulates, but it does take a lot longer to break down than other mulches. For more on wood mulch, I recommend the book The Woodchip Handbook by Ben Raskin!

• Leaves: I love leaves for the nutrition and the amazingly rich soil it breaks down in. My issue with leaves is that if you don’t shred them it tends to mat down too much which can cause the soil to become anaerobic (lacking oxygen). When shredded it’s an excellent insulator but it does have a habit of blowing all over the place in high winds. I would definitely use shredded leaves as compost though regardless.

• Hay: Hay is another great insulator and I’ve had very few issues with it myself. The only complaint I have is that if there is a lot of grass seed in the hay you tend to get a lot of grass weeds over time but that isn’t necessarily always an issue for everyone.

• Pine needles: Pine needles work great, but you do need to lay them on fairly thick to get a decent insulation layer. I didn’t notice anything substantial with the soil PH changing or anything, but needles also don’t hold water in themselves as well as other mulches.

• Straw: Definitely better than hay in most cases since it tends to not have grass seed, but it can be harder to source in some cases.

Those are some examples but remember: the best mulch is the one you have the most access to.

You want the most abundant mulch you can find!

Living Mulch

What is “living” mulch?

Living mulch refers to organic matter that is still alive when used as mulch.

The main benefits of this are that the plants you choose to use as a living mulch can be multifunctional. On top of some of the normal benefits, you can have a living mulch that also acts as a pollinator attractor, food source, medicine, and it is also actively cycling nutrients as it grows as opposed to building a new layer of soil right away.

How it works

Plants that are low growing (especially sprawling plants or small self-sowing annuals) are planted around, underneath, and between the taller plants to cover bare soil.

This allows the same water retention, weed suppression, and temperature regulation that decaying mulches have, but also allows microbes to be actively farming nutrients from the living plants.

Think of it like the difference between having a large one-time donation and a smaller but recurring one!

Examples

Similar to the point above, the best living mulch are the ones that will do best in your area.

That said, I have used the following and here are my observations:

• Cilantro: This was a new one for me, but it seems to do quite well. It forms a very dense carpet of living plants, and the soil underneath stays very moist and rich. Since it is an annual, I do have to allow it to go to seed every cycle so that it re-sows itself.

• Thyme: Thyme forms an incredible mat of dense foliage and is a perennial which is a double win for me! It has been one of the most hands-off mulches I’ve grown.

• Radishes: Radishes make a pretty good mulch especially in soil that needs to be loosened and in systems designed for regular food production. The bonus for me is that they have a little space between the foliage and the soil which allows for more airflow without the evaporation.

• Clover: I haven’t intentionally planted clovers, but I leave them when I see patches growing in the garden. I love that they act as a pollinator attractor as well as a nitrogen fixer even if I don’t normally use them for food.

• Chickweed: Chickweed grows in abundance in my region, and it forms a very nice dense carpet. It’s soft to walk on and is a great spring/fall green to eat which is a nice benefit. I wrote a recent article on chickweed that you can find here.

I suggest taking a look at what carpet-like plants already grow well around you and using that to your advantage! Yes, cilantro is great but if you can’t grow it very well then it might not be worth the effort it would take to use it as a living mulch all over your garden.

Biomass

Biomass simply refers to a large amount of organic matter.

When we talk about biomass, we’re generally thinking of sources of biomass. Biomass is what we use for mulch and is the main source (even in nature) of nutrient accumulation for soil health.

We need biomass for things like compost, mulch, fuel, fiber, and fertilizer so having abundant sources is important!

Examples

When looking for a source of biomass, consider plants that produce a lot of plant material and fast.

In our garden borage grows like a weed. I grew it one time and I can’t seem to get rid of all of it or catch it before one of them goes to seed somewhere. This might sound like a headache, but it actually makes an excellent mulch when chopped and left on the surface of the soil.

David The Good says to use your weeds too! If you have weeds growing like crazy, then chop and drop them. They may be a problem, but now they are a productive solution.

I also have peppermint growing out my ears at this particular garden, and I can’t seem to pull it out fast enough. Last summer I started using it in my fermented compost water and I found myself constantly looking for more weeds to use!

Finally, a quick (and extreme) example of why bare soil is dangerous:

The Dustbowl

In the early 1930s in the Southern Plains region of the United States, farmers had started commercially farming a lot of annual croplands. The constant tillage and leaving bare dry soil led to a severe drought (the former landscape had previously done better water retention).

This drought started a dry dust storm that swept through the entire region destroying livelihoods and leading most to migrate far away.

This (like a lot of our modern agriculture issues) could have been mitigated with proper care and attention to the soil.

It’s an extreme example of course, but there’s a real danger in not taking care of our soil and building it up.

This is important and it works! I’ve even heard of people being so successful with mulch that even in arid Arizona they have minimal water needs due to the efficient retention!

Main take-aways from this week’s article are:

• Use what’s abundant.

• Create biomass.

• Cover bare soil.