A-Mulching We will Go

Imitating Nature – But Should We Really Be Doing It?

By Elizabeth Spence

First of all, thank you very much indeed to our readers who responded to our questions about what they use as mulch and what they think about the topic in general. Your comments and information, plus our own experience and independent research are the basis for this article.

I thought this was going to be a fairly straightforward piece to write, but as I became more and more deeply immersed in the subject, I ended up wandering down all kinds of avenues I hadn’t thought about even in the deepest recesses of my imagination.

The conclusions I eventually reached were most unexpected

I hope you’ll forgive me, but the result was a fairly long piece of writing. I invite you to draw up a chair or sun-lounger, grab a cup of tea, a glass of wine or a gin and tonic and enjoy the journey. Thank you everyone.

INTRODUCTION

As a child I used to wander through the woods, kicking dead leaves, bits of old bark and twigs, sinking into mossy cushions, skipping over roots, dead trees and rotting branches, and smelling the rich, damp, earthy, woodsy aroma.

In the woodland clearings and in the wild meadows were grasses, bluebells and other lovely flowers, and not an inch of bare soil in sight.

Over the generations, the flowers had repeatedly faded, the leaves had fallen down and other woodland debris, dead insects and animals had got mixed up in everything. A wonderful protective layer had been created for the plants and trees that grew there.

When I explored beneath this litter or “duff”, or poked down around the bluebells or wild primroses or corncockles I found a fine crumbly soil – humus – over native soil.

It was decades later that I realized that what was on the ground under the trees and in the clearings was in fact nature’s way of mulching itself!

The soil, the humus, was nothing more than all this plant, insect and animal matter decomposed and decomposing with its attendant minerals, microbes and fungi, and indeed, in the woods it was the smell of the chemical compounds given off in the process of decomposition that were reaching my nose.

So why does nature mulch itself? Quite obvious really when you think about it:

- it stops moisture in the soil evaporating too quickly;
- it protects the soil from the extreme effects of sun, heat, snow, frost and torrential rain;
- it reduces the spread of soil-borne pathogens;
- it makes it difficult for certain seeds that have been dropped by birds or that have blown in to germinate – i.e. weed suppression;
- it encourages beneficial soil organisms via decomposition, and thus
- it provides nutrients for everything that lives there.

In short, it is a self-contained system that looks after itself. It is everything we want in our gardens as well, and in recent years particularly, gardeners have been trying to imitate this natural process.

Although artificial mulching of some sort or other has been used since the times of the Ancient Egyptians and has been ongoing in various ways since then, I grew up in a time and place (UK 1950s and 60s) when we seldom mulched. Only the strawberries got their straw, so that the fruits would stay clean.

It meant that you were out every five minutes watering, hoeing and weeding to keep the soil surface between the plants moist, free and open. It was just the way it was done.

But now, once you have mulch spread on your soil you are relieved of a lot of that work. That is one of the main reasons for using it.

It should be said though, that some gardeners do not use mulch at all, the reasons being

they plant very closely so that there is very little bare soil;
mulch can be quite expensive;
they enjoy the weeding, hoeing and watering;
they never have, and
they simply don’t want to.

Nowadays, there are all sorts materials that can be used as mulches. Choices depend on what sort of gardener you are.

If you are an ornamental gardener, the appearance of the mulch might be the most important thing and there are all sorts of options to beautify your landscape.

If you grow for food or are concerned about natural processes, you might be more interested in the way in which the mulch interacts with the soil and the plants.

Perhaps you want the beauty, the function and the interplay of nature all together.

As with so many topics in gardening, the merits and demerits of different types of mulches are hotly debated these days with greater and lesser amounts of evidence to back up their legitimacy.

Let’s see what’s going on.

PART ONE: INORGANIC MULCH

This is obviously stuff that is not made of plant or animal matter. With some exceptions, many of the common claims for inorganic mulch are the same as for organic mulch:

- weed barriers;
- often made of recycled material – environmentally friendly;
- keep the soil cool;
- prevent erosion;
- available in many colours;
- easy to install;
- low maintenance;
- can be wind-resistant;
- often fire-proof;

One of the major advantages of inorganic mulches, we are told, is that they do not decompose and they therefore last a long time.

Rubber Mulch

Available everywhere and made of shredded tires. It is used quite widely in playgrounds, on paths and as garden mulch.

Considerations:

it can get very hot in the sun and produce quite a bad smell;
toxic fumes if it catches fire;
doesn’t enrich the soil since there is no decomposition;
evidence of chemical leaching into the soil;
evidence that it is toxic to worms;
works its way into the soil unless you use landscape fabric underneath.

There is one type of rubber mulch made of closed cell sponge rubber, not shredded tires, which is quite inert, and claims to be the ”non-toxic” alternative.

Stone and Gravel

Stone and gravel gardens are a useful choice for plants that like hot, dry conditions.

Considerations:

can overheat sensitive plants;
debris hard to remove;
can create more alkaline soil;
works its way into the soil unless you use landscape fabric underneath.

Tumbled Landscape Glass

Also used in fire-pits and as decoration for the tops of potted plants.

Considerations:

dries out the soil quite quickly, i.e. doesn’t prevent evaporation very well;
very expensive;
debris hard to remove;
works its way into the soil unless you use landscape fabric underneath.

Lava Rock

Also used for walkways, fire-pits.

This site warns: “Wearing protective gear will help you avoid getting burned or cut by the lava rocks. . . . You should also wear a dust mask to protect your lungs from inhaling dust, goggles to protect your eyes from flying debris, and gloves for protection against cuts and scrapes”

I think we’ll leave that one there.

Plastic Mulch

This comes in two main forms.

Blue Mulch

This is made of small recycled plastic pieces

Considerations:

leaches microplastics into the soil;
doesn’t decompose;
hard to clear of debris;
works its way into the soil unless you use landscape fabric underneath.

Plastic Sheeting

Non-woven plastic sheeting is used extensively in commercial agriculture and a lot in larger home enterprises with the assertion that it encourages faster growth, earlier harvest, and ostensibly better-quality and uniform produce. It keeps the weeds at bay, the soil stays moist since there is almost no evaporation, and it is supposed to reduce soil compaction.

Plastic sheeting is usually black, but there is evidence to show that you can enhance the growth of various vegetables by using different colours.

Each colour changes the intensity of certain wavelengths of light.

For instance, early cool-season tomatoes do well on red, peppers do well on silver and this is supposed to keep aphids at bay as well, and squash and melons do well on blue.

Considerations:

Is burned, buried or dumped after use;
Reduces soil organic matter;
Changes soil microclimate and physical structure;
Contaminates soil by leaving adhered film fragments behind;
Concentrates C02 emissions through the “chimney effect” i.e. holes in the plastic.

PART TWO: SHEET MULCH

The first thing to say is that there is a fight going on in the scientific arena about whether sheet mulches should be used at all. We’ll leave that argument to them. None of the people I’ve spoken to here have a problem with it – on the whole.

Sheet mulching, as it suggests, is various-sized sheets of different materials. It can be used alone – bits of it placed on the surface between plants – but it is often applied when developing new garden beds, and the function is to kill the grass.

In the fall, you put down your sheet mulch and cover it with another form of mulch – large amounts of wood chips or shredded bark are common. Then in the spring the weeds should be dead, the sheet mulch should have degraded, and you have a lovely bed to start planting in.

So what is sheet mulch? We’ve already looked at plastic as one form of it, but there are others.

Cardboard

Many gardeners use plain cardboard as a mulch with or without covering it.

The important things to remember with cardboard are that all the plastic tape and labels are removed and there should only be black ink – the coloured ink may be toxic, depending where the cardboard comes from.

Paper

Newspaper is a traditional one, but harder to find these days. There is also kraft paper, butcher’s paper and liner board, which is the non-corrugated bit of cardboard.

Burlap

This is a natural fabric made of woven jute and will therefore decompose naturally into the soil. Old sacking was made of burlap. Recommendations are to use two or three layers and overlap sections by about 8”.

Landscape Fabric/Weed Barrier/Geotextile/Woven Sheeting

Landscape fabric is sometimes used as a mulch alone. We have seen that it is recommended for use under inorganic mulches to stop the stones, gravel, etc. mixing with the soil.

It is often used under organic mulches as well mainly as a means of keeping weeds down. We know that if we are imitating nature with organic materials, we want the interaction between the soil and the mulch, so why would we use landscape fabric?

Well, we are advised, the perforations in the woven fabrics allow water and air to get to the soil. In fact, proponents insist that landscape fabric does everything a mulch is supposed to do, especially on the weed-blocking front.

You just prepare your soil (perhaps the hardest bit), spread the fabric on top of it, attach it with special hooks (or not), make holes in it with scissors or preferably a propane torch so it doesn’t unravel, and pop your plants through the holes into the soil underneath.

There are sometimes even pre-made holes or planting lines on the fabric for exact spacing. If you don’t like the look of it, you can put a decorative mulch over it.

It also comes in different weights for your convenience. The heavier ones are used for such things as flooring in garden centres and greenhouses, and in heavy-duty landscape and drainage applications. The lighter ones are those generally used in garden beds.

However, there is a war amongst gardeners over the use of landscape fabric in the flower or vegetable garden.

Opponents worry about these things:

it’s mostly made of some type of plastic, with concern about residual microplastics in the soil, although I haven’t had a chance to substantiate this;
the really cheap ones disintegrate very quickly;

can be hard to remove because all sorts of roots quickly grow though it;

difficult to separate, move or remove plants through it.
particles of mulch, bits of soil, chunks of leaves and other debris settle in or blow in on top of it and break down, quickly blocking the perforations and completely stopping water and air getting to the soil;
this means that the surface of the fabric becomes impervious and turns into a perfect weed seed starting bed. This is what people who use inorganic mulch complain about as well. This defeats one of the main purposes – weed control;
it means that the soil structure underneath starts to deteriorate because the organisms, including worms, that rejuvenate and replenish the soil can’t function properly;
it also means that the soil can become anaerobic and compacted and smell terrible when the fabric is removed, especially with the heavier fabrics;

I have to say that all the experienced gardeners I have spoken to or who have responded to our call for information on the subject of mulches detest, loathe and hate landscape fabric because of these problems.

Some point out that in their experience, you don’t need anything, let alone landscape fabric, if you use the correct depth of mulch, because weed seeds do not have the right conditions to germinate under it.

If you do have a lot of weeds growing in your mulch, it’s probably because it isn’t deep enough. And what’s wrong with plucking the odd weed, anyway?

PART THREE: LIVING OR “GREEN” MULCH

Living mulch, as the name says, is mulch using living plants to cover the soil. The idea is that the plants do what any good mulch does: hold in moisture, suppress weeds, keep the soil covered as they allow air and water to pass through, and so on.

In the Flower Garden

I have been thinking of ground covers as living mulches in my own flower garden for a couple of years now.

To put in a new plant, I’ll separate the ground cover and dig a hole through it for the new plant, rather than clearing half of the ground cover away, discarding it and using wood chips around the new introduction. I’m learning what works and what doesn’t.

It surprised me that such a venerable publication as Fine Gardening recommends plants like Bugleweed (Ajuga reptans) and Creeping Jenny (Lysimachia nummularia) for this purpose since they are garden thugs.

But perhaps that’s the point. They are lovely and they do work as green mulches, but they definitely need a lot of watching, unless you have a very large space to cover. In that case they can indeed be wonderful. Some people use them in their vegetable garden.

Here’s where they got out of control in my garden when I had my back turned for five minutes

I am finding that the properly behaved plants that are succeeding for me as living mulches do reduce the amount of work. Some of them are:

In the Vegetable Garden

You find lists of potential plant mulches for vegetable gardens everywhere. Apart from the usual advantages of any mulch, they can also bring in pollinators.

There are concerns that the mulch plants compete with the main crop for nutrients and water, and therefore cause weaker growth and later harvests.

But what if the plants are specially selected? What if we encroach on the realms of companion planting, and start intermixing plants that are beneficial to each other, and can act as a mulch as well?

What if we create “plant guilds” with mulching as part of the process? In this system, the plants selected protect and nourish each other. The mulches can even be annual flowers if you like.

Here is a chart showing vegetables and plants that work together. Some can definitely work as ground covers.

And here’s an interesting site on living mulch as well.

Close Planting

In Jennifer’s article on growing carrots, she notes that she sows the seed much more closely than recommended on the packets. This is so that most of the space above and below ground is taken up by the carrots, so that they shade themselves and don’t allow much room for weeds to take hold. She uses a sprinkling of grass mulch, but that’s all.

Comfrey and Nettle

These two plants are mentioned very, very frequently for use as what might be called half-living mulches in vegetable gardens.

You cut them both back from time to time and chop the cuttings onto the soil between the veg. They are very vigorous, so you will have a good supply, and they produce wonderful nutrients to the soil as they decompose.

You obviously don’t want to grow the nettles in with the vegetables, so people generally grow them in separate beds out of the way.

We do in fact have one subscriber who is offering “pick-your-own” nettles. They are flowering now, so it’s a bit late to pick, but let us know if you are interested for next year!

Weeds

Yes, you heard right. Weeds. They’re only weeds because we think they are. If we think they aren’t, then the concept of them being nasty, interfering, bothersome little interlopers starts to fade away.

What if we think of them as a living mulch and valuable contributors to the health of the soil? Not only that, they are often edible or useful for medicinal purposes. Some of them are really pretty too.

Ones often recommended for a mulch application are plantain, chickweed, lambs’ quarters, purslane and white clover, all with proven benefits to the soil. Have a look at the seeds available at La Finquita in North Wallace. There are lots of options there.

If these lovely plants start getting out of hand, you prune them back from time to time and just leave the cut bits on the ground to decompose there.

Cutting them back before they set seed is probably a good idea too so they don’t go overboard regenerating themselves. Unless you want them to.

I sometimes wonder if weeds are not actually nature’s way of balancing the chemistry in the soil. Any comments?

Winter Mulch

For many years I used to “put the garden to bed” each autumn. This meant cutting down and removing all the dead plant material and applying a new layer of wood chip mulch everywhere. It looked very tidy, and I used to congratulate myself on a job well done.

Then one year I didn’t do it properly – I think I was ill or too tired or something – I just cut back the dead stuff and left it lying on the beds. Didn’t do anything else.

In the spring, the plants came up like gangbusters and I realized what an idiot I had been. Here was nature basically doing the mulching for me!

I didn’t have to cart off piles and piles of dead plant material or bring in wheelbarrow loads of wood chips all over the place. I didn’t have to do much at all.

Then last winter I went even further, and did – NOTHING. The plants gradually died down and covered the ground. Some, like the grasses, remained standing and provided food for the birds and became part of a lovely varied winter landscape.

I am definitely getting used to the tousled look in the garden.

You do tidy up a bit in the spring, but you don’t remove much.

At that time the sap is rising in you as well as in the plants, and you are usually full of gardening vim and vigour and ready to sally forth with joy into the new season, so it’s even less of a chore.

And then, of course, there is the snow itself. It’s not only nature’s fertilizer, as they say here, it’s also nature’s winter mulch.

PART FOUR: ORGANIC MULCH

Straw

Straw is a traditional and very functional mulch. Think of “straw”-berries again. Many vegetable gardeners in the area use it, although they are saying that it is getting harder to come by from local farmers. You can buy it packaged from most of the big stores.

I leave it to Magi Nams, one of our contributors to tell us about the way she uses straw mulch.

I use straw in my veggie garden because it’s light and easy to move around, it suppresses weeds, conserves moisture and decomposes nicely into the soil.
In the fall, after weeding and feeding my beds (with composted manure and/or compost), I mulch beds and pathways with straw to help prevent erosion during the winter.
In late April or early May, I rake the straw off the beds so the soil can warm and dry, and leave it on the paths between beds to help retain moisture and prevent weed growth.
During the growing season, once plants are well-established, I straw-mulch peas and potatoes and sometimes other veggies to a depth of about 6-8″.
Using the straw mulch in the garden has saved me many, many hours of weeding.

Thanks Magi!

Considerations:

introduction of weed seeds. Magi has pretty much solved this one by using a very deep straw mulch;
presence of residual herbicides and pesticides.

Hay

Hay makes a wonderful mulch. The most-often-voiced objection to using it though is that it brings millions of weed seeds with it. Yet as with straw, if you have it deep enough (6-8”), there is much less chance that the weed seeds can germinate.

Considerations:

presence of residual herbicides and pesticides

Note:

There are many, many reports about how residual herbicides in hay and straw will kill plants when used as a mulch, so it’s probably a good idea to ask questions and find out where yours comes from – including the bagged stuff.

If your plants are generally not doing well, your mulch might be behind it.

I am advised by Silvana Castillo (our first Gardening Neighbour on the site) that farmers in North Wallace do not spray their fields but use organic fertilizers, so she knows that her hay and straw are safe.

Wool

We might add it’s for the little boy that loves gardening as well.

During shearing there is quite a lot of poor-quality wool left over which is not good enough to be sent to the mills. Often it is burned, buried or sent to the landfill. Yet it makes a wonderful garden mulch. You can get it as sheet mulch, or just loose in bags. Wouldn’t black wool be cool?

Circles of the sheet version might also be an excellent option to put in the bottom of pots and containers to retain water and prevent soil leakage! Jennifer is going to give this a try.

It occurs to me that we could also use old wool blankets, cut up or not, and even bits of wool clothing as mulch as well.

I can see sculptor, Sydney Blum, who features in our art gallery section, placing highly-patterned coloured sweaters between the plants in her garden. High art, this!

We have sheep farmers in the area, so I am asking everyone to try and find out if any of them might be in a position to supply this incredible material!

Leaves

How often in the fall do we see bags of leaves at the end of driveways awaiting pickup by the garbage truck? Every time I see them, I think “What a terrible waste! Here is a free source of mulch which is just being thrown away.”

Considerations:

can blow away;
can pack down and make an impermeable layer that will suffocate everything, but there is a way of handling that:
Spread the leaves on the lawn and go over them with the lawn mower;
Or, place them in a garbage can and go at them with a whipper-snipper. They are then nicely chopped up and will not mat down;
And if you do this when nature is providing them – i.e. in the fall – they can go directly onto your beds. But you can do in anytime, of course.

Grass Clippings

Here’s another absolutely free mulch if you have lawns you keep cut – as long as you don’t use broad-leaf herbicides on them and there are no obvious things going to seed. You can collect the grass clippings in a bag as you mow, or rake them up afterwards.

The main thing to remember here is that grass, like some leaves, can mat down and turn into a nasty, smelly mess.

The secret to using them as a mulch is to cut on a sunny, breezy day and then sprinkle them onto the soil from a height, and make sure they are not more than about 1 – 2” deep. Keep them airy. That way they can dry out and start decomposing. Once they do that you can keep repeating the process.

Pine Needles (Pine Straw)

This is another free resource in our neck of the woods, but how often have I heard: “Don’t use pine needles as mulch – they’re too acidic! They’ll kill your plants!”

Are they? Will they? I went to find out.

Fresh pine needles are indeed very acidic with a pH of about 3.5. They have a resinous coating which makes them slow to break down, so they’re not doing much to start with.

Then, as they slowly start to decompose, the microbes in the soil are digesting them by taking nitrogen from the soil, but eventually the pH approaches neutral. In the end they are in fact adding nitrogen to the soil.

The only area where acidity might be a small problem is on the immediate surface of the soil. If that is a worry, then putting a layer of compost down first will put your mind at rest.

Based on the scientific literature I have consulted, the short answer is:

“No, pine needles do not acidify your soil in any way to affect your plants.”

If you want to be absolutely sure, have your soil tested at the agricultural lab in Truro.

Seaweed

Here is yet another completely natural resource for us! But see the note below the Eelgrass entry after this one for the legalities of collecting.

A large number of our subscribers have told us that they use seaweed as mulch, but there is some concern among some that it is far too salty to use straight – you need to rinse it first.

I heard one interesting suggestion that you should put it in a pillow case and run it through the rinse cycle in the washing machine before applying to the garden..

The main points here, surely, is that farmers and gardeners have been dumping seaweed straight off the beach onto their fields for centuries. There doesn’t seem to have been any problem with salt leaching into the soil and causing problems, or they wouldn’t have kept doing it.

Indeed, the science confirms that there is not sufficient salt in seaweed to make any difference whatsoever when it is used as a mulch. As with pine needles, if in doubt, get your soil tested.

It decomposes quite quickly so you might have to reapply it quite often.

Eelgrass

Here is another marine resource that has been used for centuries on fields and gardens. Everything that applies to seaweed applies here too. No rinsing necessary!

Note

On this site: Legal Info Nova Scotia, it states categorically that you have to have a permit to remove anything, including seaweed, from a beach, or you will be fined.

However, according to the Nova Scotia Fisheries and Aquaculture Department, you won’t need a lease :

“Individuals who want to harvest rockweed for personal use do not have to have a lease and may harvest in any area, including leased areas within the province unless it is an area designated as closed by the Minister.”

That’s something, anyway.

Manure

Manure, full composted, can, of course, function as mulch, but there is the downside in that it provides a wonderful bed for weed seeds.

I am finding quite a lot of uneasiness about using manure in the garden at all.

It appears that if the animals have eaten fodder treated with herbicides or pesticides, these will remain in the manure for a couple of years and affect crops it is spread on. Have a look at this report if you want to follow it up.

Similarly, if animals use salt licks, there is a chance this will pass into the soil as well.

I suppose the only advice here is: know who your supplier is (even the cow or sheep, if you’re so inclined), and if in doubt, get your soil tested.

Compost

Extremely well decomposed compost can cause a bit of a problem on the garden as a mulch because, like manure, it is a great place for weed seeds to germinate.

Since it can be very fine indeed, there is a chance too that is may become very compacted.

Sawdust

Sawdust too can compact down, develop a crust and interfere with the gas exchange at the interface. I would just use it in the compost heap or mixed with something else.

Bark

Many of our readers use some kind of bark mulch from cedar, pine or hemlock trees. You can get it bagged in various colours as well. the most common ones available around here are:

Kiva-Marie Belt of Seafoam Lavender Company and Gardens, a very popular and successful grower and garden centre in our area, tells us:

“We use cedar bark and pine bark mulch here at Seafoam Lavender, often overtop cardboard or paper. We choose bark mulch for three reasons:

(1) it’s locally available,

(2) over a long period of time it has helped to loosen our heavy soil, and

(3) it offers excellent weed suppression, allowing us to stick to our practice of spray-free gardening.”

That’s recommendation enough, isn’t it? Thanks Kiva-Marie!

Bagged bark comes shredded or in nuggets.

The main thing about nuggets is that they should be big enough to recognize as bark and they are seldom dyed. You know what you are getting. Or do you? Compare the prices of these. They are both called nuggets, but why is one so much cheaper than the other? The one on the right doesn’t even look like nuggets.

Well, it’s probably the same as what happens when it comes to shredded bark. Since it is shredded and usually dyed, you can’t really tell what it is.

I go into this a bit further down, but let’s just say that the cheap one is likely to contain non-bark products.

When it comes to their uses in the garden, some people hate the look of nuggets; others love them as interesting landscape statements.

Shredded bark is better in some ways because it knits together and doesn’t wash or blow away as easily as the nuggets do.

Dyed Mulch

The noise around this topic is deafening, the main question being whether the dyes are toxic contaminants or not.

On the whole, it seems that responsible companies do not use toxic dyes, but how do you know if the maker of your bag of dyed mulch is a responsible manufacturer? You don’t, unless you ask, and even then you might not get an answer.

For some time, Jennifer has been on the back of the Fredericton suppliers of bagged dyed mulches that are available at Foodland and Home Hardware in Tatamagouche.

She eventually managed to get hold of them and they assured her that all their dyes are water-based and therefore safe.

Users report the dye coming off on their hands and being quite hard to remove. A bit of a pain, I would have thought.

Dyed mulches usually fade after a while, but fear not! There is a solution you can spray on to rejuvenate it:

Wood Chips

A wood chip is a wood-chip is a wood-chip. Right? Wrong!!

The first thing for us to know is where our wood chips come from.

Dyed Wood Chips
If you buy a bag of dyed wood chips with no indication of what they are or what tree they are from, it is highly likely that they are actually building and demolition waste: ground up pallets, cut-offs potentially treated with wood preservative (nasty), or beams from ancient houses conceivably with residual arsenic or even lead paint.
This type of chipped wood is particularly good at taking up dyes, and dying evens out the colour of all the different types of wood.
This applies to bark mulch as well, especially if it contains other wood products, which the cheap ones probably do. But doesn’t it all look nice?
In Jennifer’s investigations into the source of locally available bagged mulch and bark, the manufacturers assured her that they did not use “pallets or waste-wood.”

RCW Chips
Then there are RCW chips. RCW stands for “ramial chipped wood.” “Ramial” means “to do with branches” and these chips are indeed made from small to medium sized branches.
The point here is that the smaller branches of a tree have higher densities of nutrients, and as they decompose on the ground they provide more nourishment to the soil than ordinary wood chips. More expensive.

Engineered Wood Fiber (EWF)
One of the commercial names of this product is Fibertop and it was initially intended as a safe playground surface.
It is made from 100% forest wood – not recycled wood – and it is ground, screened and blended together.
I contacted the company to see whether it would be suitable as landscape mulch and I was advised that it would be very good for that. They also assured me that no chemicals were used at all in its manufacture

Arborist Wood Chips
This is what we see along our roads as government crews chip up felled trees, branches, leaves, needles, etc.
Local woodsmen supply it to us gardeners as well. It is a readily available mulch source around here.
In fact, one subscriber saw a government chipper near her house, and asked them if they would dump the chips on her land. They did!

The objection that inevitably comes up regarding wood chips is that they deplete nitrogen from the soil causing poorer results for your harvest.

Here’s the answer based on my reading of the scientific literature:

There is indeed a small amount of nitrogen exchange at the interface – i.e. between the mulch and the top few millimeters of the soil.

But even shallow-rooted plants tend to take up their nitrogen lower than this as they absorb water through their roots.

Nitrogen can lurk very deep in the soil, therefore the surface mulch has little or no effect on the plant’s nitrogen uptake.

There is a caveat though! If you dig in un-composted woodchips or indeed any other undegraded organic matter into the soil, then you might have trouble with nitrogen depletion.

Just make sure you keep your mulches on the surface. This is important.

If in doubt, get your soil tested.

PART FIVE: FINAL THOUGHTS AND RECOMMENDATIONS

Fire Safety

Some of our subscribers are woodlot owners and very involved in forest safety in Nova Scotia. When I wanted to discuss garden mulching to them, they looked at me in horror and dismay.

“How can you use that stuff with all the wildfires we’ve been getting?” they said, incredulously.

“Don’t you know it’s a fire hazard near houses?

“Don’t you know that you’re not supposed to have any woody stuff at all anywhere near a building? That includes trees and shrubs!!

“Don’t you know that houses have burned down because the mulch caught fire?”

I had to admit that I didn’t know that.

I do now, especially after having read the Firesmart Guide to Landscaping which my forest pals gave me.

Jennifer’s husband, Mark, is the fire chief in Tatamagouche, and he of course agrees that, “Any combustible material near a structure clearly increases the fire risk. It is literally fuel for the fire, and mulch falls into that category.”

As I am writing this, Jennifer contacted me to say that Mark had just returned from a fire call in where a home nearly burnt down because someone threw a cigarette into some mulch next to their deck.

The TFD were able to put the fire out, but Mark commented that this is quite a common occurrence: there have been a number of other houses in the area that have burned for the same reason.

So what about spraying fire-retardants on mulch?

Here’s your answer.

I don’t know how it would affect any plants.

Research is underway into mulch flammability. Here is a 2023 Study

Although the study is not complete, decomposed bark mulch looks to be the least likely to burst into flames.

If we want to be completely fire-aware, we might want to limit mulches around our houses to stone, gravel and living mulches. It looks like our ideas about foundation plantings are going to have to be completely changed.

And we have to realize that not only wildfires cause mulch to burn – we do as well.

General Recommendations

Think about what sort of garden you have or are aiming for. What is generally important? Art? Food? Pretty on the Eye? Natural? Modern? Not bothered as long as it’s tidy, etc.

What you want your mulch to do for you. Look nice? Interact with the soil? Just stop the weeds? Reduce the amount of work in the garden? Don’t care?

If you just want a garden as a horticulturally non-functioning landscape, then the inorganic, coloured mulches might be for you.

If you are growing vegetables and you need to access the soil from time to time, a light mulch like seaweed, hay or straw is best, since you can move it around easily.

If you are looking to mulch around trees, shrubs or perennial beds where you are not going to be fiddling with the soil very much, things like wood chips and bark are quite suitable.

Use what nature provides for us – FREE.

Use the correct depth of mulch:
- 3-4” for most things;
- about 1-2” for grass clippings
- 6-8” for fluffy things like straw and hay.

The depth of mulch you use on your beds is very important, because if you use too much, your plants may fail because water and air cannot get through to the soil, or water already there cannot evaporate and things will drown.

So many of the bought mulches come with potential dangers and can become very expensive, so it really pays to investigate where they come from.

There is also something called TOXIC MULCH SYNDROME where poorly stored mulches become poisonous to plants and will kill them if applied.

Do not pile up mulch around trees and bushes, since this causes girdling, that is to say, roots will grow into it and start strangling the tree.

Mulch quite often finds its way from the garden bed to the pathways or the lawns. Living where we do, some of our subscribers have regular gale force winds in their gardens and even the heaviest mulch is blown away.

One solution to this might be to use pieces of sheet mulch weighted down with stones here and there – wool sweaters would be lovely!

There is actually a product available to try and stop mulch flying away:

In the end, the use of mulch has to be an entirely a personal choice based on availability, cost, type of garden, the space you have and your aesthetic. There are no laws. There are lots of questions and uncertainties though.

Are we Really Imitating Nature?

In some ways we could say we are imitating nature when we use blue mulch or tumbled glass to look like a river running through our property. “It looks so natural!”

But does the way we use mulch actually do what nature does?

In the introduction, I described how, as a child, I had observed the way in which nature mulches itself. It does it very slowly. The process is not strained, the materials drop as the gentle rain from heaven upon the place beneath, to be Shakespearean about it.

When we handle organic mulches we tend to fling them around in huge shovelfuls sending all sort of particulate matter and fungal spores flying into the air.

Our local Professor of Mycology (fungi studies) tells me that BILLIONS of fungal spores are released when we disturb mulch like this. They are happiest when they land on moist organic surfaces where they can do the things they do best – eat and reproduce.

Dr. Christopher Moss, a GP now retired from Tatamagouche, explains that the fungi in organic mulches can easily be breathed in and cause all sorts of allergic reactions, but more worryingly, diseases such as fulminant mulch pneumonitis and pulmonary aspergillosis. These are potentially fatal fungal diseases of the lungs.

Luckily, Dr. Moss emphasizes, they are very rare, and our immune systems usually prevent them taking hold, but if your immune system or your lungs are compromised in any way, you might want to keep this at the back of your mind. Masking might be an option.

When it comes down to it, we are only using one of the fundamental principles of natural mulching, that is to say: covering the soil – and only sometimes do we do it with organic matter.

Almost everything else in the way we mulch and in the results of our mulching are different and perhaps we are paying the price.

Indeed, we have found out that the use of mulch can:

kill your plants;

kill you;

give you a fine, and

cause your house to burn down.

Maybe we should stick to stones, gravel and living mulches around the house.

Perhaps we should even follow the non-mulchers.

At least then we would be breathing a bit more easily.

In order not to overburden this article, I have not included notes or references. If you would like to see any of the sources, please let me know

4 Responses

Mary Maron says:

1 August 2024 at 5:09 pm

Elizabeth, you wrote a thesis on mulching! A+ for your research and presentation. You have given me a lot to think about. Thank you!
Elizabeth Spence says:

1 August 2024 at 6:04 pm

Thanks so much, Mary. It was a bit like being back at university, but it was great fun, and I learned so much too!!
Jean MacDonald says:

1 August 2024 at 10:20 pm

Wow, the article on mulching was very detailed and informative, well done!
1. Elizabeth Spence says:
  
  2 August 2024 at 9:00 am
  
  Thanks Jean!

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