Mulching

Sugar cane mulch is great for vegetable beds

“Make your soil as healthy as a forest floor, by mulching!”

Mulching is the covering of soil with organic material. It is much the same as what naturally occurs in a forest when leaves fall to the floor. Mulch suppresses weeds and prevents evaporation, which allows the topsoil to remain moist so that earthworms and other creatures can live there.

Benefits:

  • Saves water
  • Builds soil life
  • Suppresses weeds
  • Becomes fertiliser

Jump to:

Why Mulch?
Types of Mulch
Homegrown Mulch
Free Mulch
Straw Mulch
Local Byproducts
Purchased Screened Mulch
Mulching Techniques
Mulching for Vegetable Beds
Leaf Mulch
‘Chop ‘n’ Drop Pruning’
Mulch Basins For Trees
Sheet Mulching
Lasagne Gardening
Green Mulch (Living Mulch)
Frequently Asked Questions
How much mulch do I need?
How often should I mulch?
Where can I get free mulch?
Should I water my mulch?
What about termites?
Related Articles
Sheet Mulching
Lasagna Gardening
Chop ‘n’ Drop Pruning

Why Mulch?

Sugar cane mulch is a wonderful soft mulch, perfect for vegetable beds

Sugar cane mulch is a wonderful soft mulch, perfect for vegetable beds

Mulching mimics the ground cover of natural forest systems, and so brings the benefits of forest ecology into urban developments. You can deliberately mulch an area to better retain water, to stimulate soil ecology and to eventually fertilise your gardens when it breaks down. Mulching will also reduce weeds – especially a thick mulch – by reducing the amount of sunlight available to the soil.

Types of Mulch

Every kind of mulch will have it’s own qualities and potential, and certain mulches suit certain uses better than others.

Homegrown Mulch

Homegrown mulch can be anything from leaves, stalks or grass clippings to your own wood chip mulch from trees and branches that have fallen. Any organic material that would otherwise be thrown in the bin can become mulch for your garden.

The simplest way to manage your own homegrown mulch is to ‘chop ‘n’ drop’, whereby anything you prune or pull out of the ground is simply dropped on the soil to become mulch. This is a gradual approach and can look messy, but it mimics a forest floor almost exactly.

Another option for managing homegrown mulch is to use a chipper, shredder or other mulch-making machine. These can be especially good for dealing with fallen branches, and some can handle logs. Wood chip mulch is excellent mulch.

Some plants are grown specifically to produce mulch. They are fast growing plants, often grasses such as broad-leafed bamboo (clumping varieties only!) and sugar cane, which can also be grown as a shade screen in summer, and chop ‘n’ dropped in winter to let sunlight in. Deciduous trees can serve the same purpose, but naturally drop their leaves in winter.

Free Mulch

A load of free mulch; a mix of wood, leaves and branches from a variety of trees

A load of free mulch; a mix of wood, leaves and branches from a variety of trees

When tree-loppers and tree surgeons prune and chop down trees, the offcuts are often chipped and carried in a truck. You can put your hand up and ask them to drop a load at your home. Get in contact with a local lopper.

Because free mulch is usually a mix of leaves, branches and wood chips, and also a mix of different trees, it brings a variety of nutrients and environments to your soil, which is why some groups champion it as the best mulch.

Straw Mulch

Straw mulch is a great all-round mulch. If you're buying some, ask for 'spoilt straw'

Straw mulch is a great all-round mulch. If you're buying some, ask for 'spoilt straw'

Straw mulch is just straw, hay or any other dry stalks. It’s very effective as a soft mulch for vegetable beds, because it can be shifted easily when you’re transplanting, and it will break down faster than wood chip mulch. Straw mulch is a particularly good insulator, as the stalks trap air which takes a long time to heat and cool. The result is that soil temperature is moderated more, and life developing within narrow temperature ranges can sustain.

You can buy straw mulch in bales, and if you ask for ‘spoilt straw’, you might get some for cheap. You can also integrate keeping chickens, laying straw for their bedding, then using soiled bedding as mulch in the garden, or involving it in your compost.

Local Byproducts

Wood shavings and sawdust are byproducts of sawmill operations

Wood shavings and sawdust are byproducts of sawmill operations

Find out what kinds of organic material might be produced in your area as a byproduct of a larger operation. For example, timber mills throw away tonnes of wood shavings, and lawn-mower men throw away bags of grass clippings. For free, or for a small trade they might be happy to let you take it off their hands.

Purchased Screened Mulch

Check out businesses which sell organic mulches of different types and grades. Go and have a look at what’s on offer, and it’s likely you’ll find something suitable there.

Be careful ordering mulches you haven’t seen or learned about. Some popular coloured mulches are from treated wood, which leaches arsenic into your soil and shouldn’t be touched. Also the colouring might have chemical agents added. Rubber-mulch likewise leaches and is really best suited to playgrounds and ‘toy gardens’

Mulching Techniques

There are many good uses for mulch, and depending on the use, different techniques and mulches can be implemented.

Mulching for Vegetable Beds

Soft mulch in a wicking bed is easy to dig through

Soft mulch in a wicking bed is easy to dig through

For veggie beds which you plan to dig into a lot, I recommend choosing a soft mulch such as straw, hay or grass clippings, which can be cut through with a scoop, and planted through easily. Be careful with grass clippings from grasses with seeds or runners – it’s better to compost these.

You can use fresh compost, manure or worm castings as a mulch, and it’s best in an area of dense growth where it can remain moist and will be out of direct sunlight. For open areas it’s best to mulch OVER compost or worm castings with something else.

Leaf Mulch

Leaves make excellent mulch, but have a tendency to blow around in the wind. You can keep leaves where you want them by either applying something over the top to weigh them down (such as compost or manure), or you can grow a ground-cover plant (see Green Mulch) which will stymie the wind and physically hold the leaves in place.

‘Chop ‘n’ Drop Pruning’

A good way to ensure there’s mulch where your plants need it is to ‘Chop ‘n’ Drop’. When you’re pruning, thinning or harvesting, just drop all the offcuts to the ground around the plant or around neighbouring plants. It seems lazy and can even look messy, but this is how forests mulch their floors, and it’s also a great way to cycle what you might otherwise throw in the bin.

Mulch Basins For Trees

Trees drop their leaves around themselves, and encourage soil life to move there. Mulching around a tree is a great way to improve the lifestyle of your trees. While you’re at it, consider mounding a raised ring around each tree to form a basin shape. This will help concentrate water toward the centre. Depending on the needs of the species, the basin can vary in size, but for all cases make sure the mulch is not riding up around the trunk – it should meet the tree at ground level (otherwise the tree may rot).

Mulch basins can be integrated with a greywater system to naturally filter greywater and deposit it below the surface.

Sheet Mulching

Before sheet mulching - grass and weeds have overgrown the area

Before sheet mulching - grass and weeds have overgrown the area

Sheet mulching is when a blanket layer of organic material (usually cardboard) is spread over an area of land, and then covered with other organic materials (usually tree mulch). It is an excellent technique for covering and killing grass and weeds, and, depending on what other materials are added, sheet mulch can be planted through and into.

After sheet mulching - without sunlight the grass and weeds die and break down

After sheet mulching - without sunlight the grass and weeds die and break down

Before the blanket layer is added, there is an opportunity to apply soil amendments, such as fertilisers, pH balancing agents, clay or gypsum.

There are many variations that gardeners have introduced to the practice of sheet mulching, my favourite of which is the practice of lasagne gardening.

Lasagne Gardening

Lasagne gardening is when multiple layers of organic materials are built up over an area of land which creates an instant garden bed, ready for planting. It is an elaboration on the basic process of sheet mulching, and is an excellent way to start growing over a sheet mulched area while you wait for the soil below to improve.

  • Follow the first steps of a sheet mulch – lay down soil amendments, then cover the area with a blanket of cardboard (or newspaper, bed sheets), but don’t mulch over the top just yet.
  • Add layers of compost, leaves, shredded newspaper or plain cardboard, straw, worm castings, good soil, grass clippings (not too much), kitchen scraps, manure, seaweed, weeds (before they seed!). The area should mound up, but remain flat across the top.
  • Cover the top with mulch (soft mulch is best) and the area is ready to plant.

Lasagne garden beds are interesting, because they create an active quasi-composting environment as all the fresh materials mix and break down. This generates warmth, and if timed well, or in conjunction with a temporary green house, you can grow crops out of season and avoid frosts. In areas with harsh winters this has great potential.

Sweet potato creates a wonderful living mulch

Sweet potato creates a wonderful living mulch

Green Mulch (Living Mulch)

Green mulch is a completely different way of thinking about mulching. It’s when small ground-cover plants grow over an area of land and shield the soil from direct sunlight. Green mulch occurs in forests, and has many benefits there. The shade and shelter allow creatures to roam the forest floor without exposing themselves to predators. The plants also create an insulated, humid and oxygen rich environment, perfect for micro-organisms to proliferate. Green mulch requires moisture to grow, but still prevents more evaporation than leaving soil exposed.

There are many plants well suited to green mulching. Alfalfa, clover and lupins are popular choices worldwide, and bring an added benefit of nitrogen fixation, which means they improve the soil as they grow (they are also edible!). However, even local weeds provide ground cover, and will grow without assistance (this practice is important for revegetating deserts).

Frequently Asked Questions

How much mulch do I need?

Your mulch can be as thick as 30cm without restricting airflow. I recommend a minimum of 10cm thickness to ensure your soil is protected from direct sun.

  • Multiply the length and width of the area (in centimetres) and multiply that by 10 (cm thickness). Finally divide by 1000000 to get the minimum cubic meters of mulch. Seems complicated? Here’s an example:
  • For a 5m by 5m area of land,
  • 500cm x 500cm x 10cm = 2500000cm^3
  • 2500000 / 1000000 = 2.5cm^3 (apply 2.5 cubic meters of mulch)

The maximum mulch for this area would be 7.5 cubic meters, so there’s plenty of room for variation.

How often should I mulch?

A coarse mulch will take longer to break down than a straw mulch. Maintaining a 10cm thickness over your soil may require half-yearly applications, or for coarse mulch once per year will be ample. As your soil life builds up it will break down mulch quicker, and in established gardens even coarse mulch can be all but gone in one year (that is excellent!)

Where can I get free mulch?

Call your local tree loppers or tree surgeons, and give them your address and phone number. Next time they do work in your area they may call you and confirm your address as a place they can dump mulch. It’s never certain that you will get mulch, and the amount of mulch you receive will vary and you must be prepared to receive a full truck load (up to 10m^3). Nevertheless, free mulch is excellent mulch, and it’s a great way to recycle local organic waste.

As for straw mulch, if you know anyone keeping rabbits or chickens who aren’t re-using the soiled straw bedding from their cages and coops, you might be able to take it off their hands for free, or help them lay fresh straw in exchange for free straw.

Should I water my mulch?

You can water your mulched gardens as per usual, but you don’t have to water as often. Mulch will prevent evaporation, and as it breaks down it will hold moisture in the top layer of soil. You should find your plants can go longer without watering if the soil around them is mulched. Scratch the mulch away and see if the topsoil is still moist, or wait until plants show signs of struggle.

What about termites?

Termites may use your mulch to travel through, and will have a go at the wood chip mulch that’s touching the ground. However, termites are nothing to be afraid of – only respected. Ensure any wooden structures are kept dry and off the ground, and let termites assist in the rapid breakdown of your mulch. Encourage as much life as possible in your garden and termite populations will be naturally regulated by birds, ants, geckoes and nematodes.

Related Articles

Sheet Mulching

“Sheet mulching is one of the best things you can do for your yard or garden!”

Lasagna Gardening

Chop ‘n’ Drop Pruning

6 comments on “Mulching

  1. I live in Scottsdale AZ and thought that in the desert if we left our freshly pulled plant material on ground it robbed the soil of nitrogen until it was seriously broken down. There is big issue of lack of nitrogen and very high PH here.

    • Hi Linda, thanks for your comment. I’ve had a look at Scottsdale’s climate and gee-wiz you guys don’t get a lot of rain!
      I would love to share with you what I’ve learnt about arid climate permaculture, but it really depends on what you’d like to achieve with your property. This video shows how anything is possible…
      http://www.youtube.com/watch?v=sohI6vnWZmk
      I hope you find that interesting.
      Good things

  2. Linda I’ve had the same problem with mulch. I have even laid compost down and still had it happen. I guess my compost wasn’t very high in nitrogen because adding nitrogen fertilizer worked great. Good manure under the mulch would have been more appealing. It is an important point you make that mulching doesn’t automatically add nitrogen. My guess is that I lose nitrogen in my compost because it drys out so fast and any natural ammonia would be dissolved in that water.
    As far as the alkalinity I have never tested but will not hesitate to add sulfur to lower my pH once I find out. That is now that you have peeked my curiosity.

    • Dear Drake and Linda,

      Sorry for not having addressed your issue directly; I hope the video gave some insight.

      There are two suggestions I have for you guys to consider.

      Firstly, to retain moisture and begin the process of balancing any soil ph issues, you must cover your soil. I recommend wood chip or street tree mulch. Don’t worry, it won’t rob your soil of any nitrogen. This is a first step toward encouraging life into the soil. With life comes aeration and a correction of soil ph (a long term correction). With exposed soil you will only see depletion.

      Secondly, get your hands on some seeds for nitrogen fixing legume trees (I recommend leucaena if you can find it). These pioneers have evolved to grow in harsh conditions and improve the soil as they grow. They send a deep taproot down and can often survive with no watering. They take nitrogen from the air instead of from the soil, and they actually fix nitrogen into the soil, which enables other plants around them to grow. You can also periodically cut down a nitrogen fixer to release large doses of nitrogen into the soil, and you should see a boost in the surrounding plants. N-fixers include peas, beans and clover, and can come in the form of trees, shrubs, ground covers and vines. Its common practice in permaculture to grow an n-fixer next to a tree you want long term, to nurse it along. Once the young tree is established, you can chop down the nurse tree.

      I dont live in an arid climate, but not too far off. If i were in your shoes i would both order a payload of mulch, and plant as many n-fixers as possible on my property. Given a year or two, im sure the soil would be able to grow more demanding plants.

      I hope this helps you both

      Good things

  3. Thanks Shaun I was listening to a discussion on wood chips and straw. What my mistake probably was, was to mix organic matter into the soil. Not really a mistake just that it robbed the soil of nitrogen. No dig gardening is what I’m moving toward in the sense that I learned to till the soil and its taken me quite a few years to savy-up. Got some good self sown tree growth now. Some rough areas have digested the sticks and boughs laid down. I still have to do stuff the old fashioned way in the vegi patch to please my Wife. Though if I can get a little ahead of her I have a few ideas -all of which include mulch.
    I may still have access to the local version of leucaena that I have seen growing on a neighborhood lawn. One got chopped but I think another is still around. I scattered various leguminous tree pods around the last few years so I may already have one. Lobardy poplar is the invasive monster that generated a huge amount of sticks for me. I sent out runners everywhere when I cut it down. It started from a rootless branch dug into the ground.

    Since my last post I have been diligently mulching. One bed with a mix of newspaper mush, compost and steer manure which has a pleasing black soil look to it and other bare places with clippings. I got a bunch of composted steer manure so getting that on my pathetic lawn is priority. I need a good source of mulch. The easiest thing to buy, transport and spread for me has been straw so I’ll probably stick to that until I miracle into a pick-up truck. Your advice is well taken – this time I will ask if they have “spoiled” straw.

    • Hi Drake,

      Sounds like you’re changing the world alright. With your tree cover going up, and your soil covered, soon your soil will be looking after itself. I started with sand which wouldn’t even grow couch grass, and 3 years later I’ve got potatoes and sweet potatoes growing without any watering. All I do is harvest that patch. It’s taken some effort in the beginning, but if the trees and plants are growing where they like to grow, you find yourself stepping back more. I’m looking forward to a backyard full of fruit and nut trees, perennial vegetables and self-seeding vegetables growing like weeds. I’ve seen it done.

      If there are any tree surgeons/loppers operating in your area, give them a call and ask if they’re chipping/mulching. These guys need a place to dump their loads, and around here they have to pay to dump it in landfill, so they jump at the chance to drop it on your verge. That’s about the best mulch you can get too – it’s trees (leaves, bark, wood, twigs, all different sizes), and it takes a long time to break down. In the meantime, straw is an excellent mulch, and very easy to dig through, ie in a vegi patch.

      I wish you all the best, and I hope others flock to your place to see how they can solve the low-nitrogen, low-rainfall situation on their own properties!

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