This page lists some of the more common mulching materials available. It is by no means a complete list, but all the mulches mentioned below are ones that I currently use or have used in the past.
The key factors in determining what are the best mulches for your garden are cost, quality and what is available.
For example, straw and horse manure can often be obtained for free, but it contains a lot of weed seeds. Whereas sugar cane mulch is expensive and comes wrapped in plastic, but it is a high-quality mulch that has no weed seeds in it. There is no best option, rather it is a matter of what suits your needs based on budget and availability.
All mulching materials can be spread directly on vegetable beds, but most will be improved if they are processed first. There are three ways that mulch can be processed to improve its quality.
- BUYING SPOILT MULCH
It is possible to buy mulching material (straw, hay, pea straw and Lucerne) that has already begun to break down, either from water damage or age. This older, poorer quality material is generally easier to spread and breaks down more quickly than fresh mulch. - PROCESSING MULCH BY HAND
This involves heaping mulching material in the open to expose it to the elements, turning and watering it to hasten the breaking down process. - PROCESSING MULCH THROUGH A DEEP LITTER CHICKEN PEN
This involves spreading the mulching material in a pen that chickens have constant access to. As the chicken’s scratch at the material not only do they break it down they will fertilise it in the form of their own manure. This is my preferred method of processing mulch. For information see Deep Litter Chicken Pen.
Processing mulch through a deep litter chicken pen is a good way to make mulches finer as well as removing weed seeds and adding manure.
sugarcane mulch
When sugar cane mulch first came on the market I was sceptical of it from an environmental perspective. It comes wrapped in plastic and, given that I live in Victoria, hundreds of kilometres away from where it comes from in Queensland, it usually has to be transported great distances. However, it has two big advantages, the mulch is exceptionally fine, so it does not have to be further broken down before spreading it, and it has no weed seeds in it.
Though it rates relatively poorly in terms of environmental impact I have found it useful for mulching pots and as a backup when I run short of my deep litter processed straw and pea straw mulch.
While being the finest mulching material on the market and completely free of weed seeds it comes wrapped in plastic.
ADVANTAGES SUMMARY
ADVANTAGES
- Fine mulch that does not need to be processed before being used.
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Contains no weed seeds.
DISADVANTAGES SUMMARY
DISADVANTAGES
- Comes wrapped in plastic.
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Has to be transported long distances.
Straw
This is the mulch that I use the most of, primarily because it is relatively cheap, can be easily sourced locally and contains fewer weed seeds than hay or pea straw. However, it makes a better mulch if it is processed before spreading and is not as nutritious to your soil as nitrogen fixing plant mulches, such as pea straw and Lucerne.
These days straw is the most common mulching material that I use.
Bales of straw. If you can source spoilt straw (straw that is old or damaged by water) it can sometimes be picked up at a cheaper price. Spoilt straw is ideal for mulching purposes.
ADVANTAGES SUMMARY
ADVANTAGES
- Relatively cheap.
- Contains few weed seeds.
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Easily sourced locally.
DISADVANTAGES SUMMARY
DISADVANTAGES
- Low nutrient value.
- Hard on the hands if you handle it without gloves.
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Needs to be processed to turn it into fine mulch.
Pea straw
Pea straw is dried pea bushes after the pea crop has been harvested. Being a nitrogen fixing plant it has a higher nitrogen content than straw. It used to be extremely cheap, but as its benefits as an organic mulch became more widely known its price went up considerably. However, it is still much cheaper than Lucerne, the only other nitrogen fixing plant that is readily available as a mulch. But it is harder to spread in its unprocessed form, it needs more processing to turn it into an easily spreadable mulch than most of the other mulching materials. Like straw and hay, it can contain weed seeds. But it also often comes with pea seeds. As most of the peas that are grown are not fresh picking peas these sprouting peas in pea straw mulch are a nuisance as they will not grow into anything useful to the average food gardener.
On balance pea straw is quite good as a mulching material. It is the second most common mulch that I use.
ADVANTAGES SUMMARY
ADVANTAGES
- Richer in nitrogen than straw.
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Cheaper than Lucerne hay.
DISADVANTAGES SUMMARY
DISADVANTAGES
- More expensive than straw.
- Contains both weed and pea seeds.
- Harder to spread in its unprocessed form.
hay
Cheaper than Lucerne and contains more nutrients than straw, but it has some serious drawbacks. As it is made using mature cut grass it can contain a lot of weed seeds. An even bigger problem is that some grasses will sprout from the tiniest of pieces, turning the hay itself into a weed problem.
To minimise these risks grass hay needs to be heavily processed before being spread on vegetable beds. For this reason I rarely use hay as a mulching material.
As well as potentially carrying lots of weed seeds some grass hay can sprout from tiny pieces of itself. LEFT: A piece of grass hay that has sprouted. RIGHT: What happens when lots of pieces of grass hay sprout.
ADVANTAGES SUMMARY
ADVANTAGES
- Cheaper than Lucerne hay.
- Contains more nutrients than straw.
DISADVANTAGES SUMMARY
DISADVANTAGES
- Can contain lots of weed seeds.
- Some species of grass hay can sprout from tiny pieces of itself.
- Is more expensive than straw.
Stable Sweepings
Stable sweepings are mainly made up of straw used for horse bedding in stables, though it may also contain some scraps of hay and chaff.
Its main advantage it that it is considered in the horse industry as a waste product, so gardeners can usually get it for free. It also contains plenty of horse manure. But horse manure can contain lots of weed seeds embedded in it as such seeds are not killed when they pass through a horse’s digestive system. Of all the mulches stable sweepings is the most likely to introduce unwanted weeds to your garden.
In the past I regularly used stable sweepings, but in doing so I inadvertently introduced several new weeds to my garden. So these days I mainly use straw and pea straw as they contain fewer weed seeds.
ADVANTAGES SUMMARY
ADVANTAGES
- It is usually free.
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Rich in nitrogen due to being laced with horse manure and urine.
DISADVANTAGES SUMMARY
DISADVANTAGES
- Contains lots of weed seeds.
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Often comes with other contaminants such as plastic, tape and even the odd syringe.
Lucerne (Alf Alfa)
Lucerne is a nitrogen fixing plant used to make high quality stock fodder.
As it is high in nitrogen it makes it a very desirable mulching material for gardeners. However, its value as stock fodder makes it very expensive. Weather damaged Lucerne can sometimes be obtained at a cheaper price but even then it is the most expensive mulching material on the market.
While Lucerne is considered the king of mulches I rarely use it as there are so many other mulching materials around that are almost as good but much cheaper.
ADVANTAGES SUMMARY
ADVANTAGES
- High in Nitrogen.
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Easier to spread in its unprocessed form than pea straw.
DISADVANTAGES SUMMARY
DISADVANTAGES
- Very expensive.
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Is hard on the hands when handling it without gloves.
Lawn clippings
Not the easiest of mulches to work with as, if applied too thickly, it can turn into a smelly slimy mess. It also can contain weed seeds.
However, if applied thinly it can make a useful mulch. Its biggest advantage is that, if you are using your own lawn clippings, it is not an external consumable import. Minimising the number of imported consumables used in a garden is a good environmental goal to work towards.
In the warmer months I routinely spread thin layers of grass clippings, especially on general garden beds.
Lawn clippings spread on a vegetable patch. If spread thinly they can make a reasonable mulch.
ADVANTAGES SUMMARY
ADVANTAGES
- Non imported consumable, if using clippings from your own lawn.
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Free.
DISADVANTAGES SUMMARY
DISADVANTAGES
- May contain weed seeds.
- Can be smelly and slimy if applied too thickly.
Pine needles
Pine needles have a low PH (acidic) which makes them unsuitable as a general mulch unless your soil is alkali. However they are ideal for plants that love acid soils such as blueberries and raspberries. It can usually be collected for free as most towns and suburbs have some pine trees accessible to the public. Simply rake up the fallen pine needles under the trees and take them home to your garden. The acid soil conditions the pine needles create also inhibit the growth of weeds that prefer alkali soils.
The main disadvantage with pine needle mulch is that it usually comes with pine sticks and twigs, which do not break down easily.
Pine needle mulch under raspberry bushes.
ADVANTAGES SUMMARY
ADVANTAGES
- Ideal for acid loving plants such as blueberries and strawberries.
- Usually is available free of charge.
- Inhibit the growth of weeds that like alkali soil.
DISADVANTAGES SUMMARY
DISADVANTAGES
- Not suitable for plants that prefer alkali soil.
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Contains sticks and twigs that take a long time to break down..
Whether pine needles lower soil pH disagreement
Note that there is some disagreement as to whether pine needles lower soil pH with some individuals and websites claiming that it does not lower the pH.
In 2023 I ran a series of pH tests on pine needles which involved placing some needles in a container of Ballarat tap water (which is very alkaline) for two weeks and comparing it with a container of water that didn’t have pine needles added. The pine needles dropped the pH of the water they were in by at least 1.5 on the pH scale, turning the water quite acidic.
LEFT VILE: Tested water that did not have pine needles added to it. RIGHT VILE: Tested water that did have pine needles added to it showing the significant drop in the pH level.
Based on these test results I believe that rainwater peculating through pine needles will leach some of the acids out of the needles and into the soil below, thereby at least temporarily dropping the pH of the soil.
Sawdust
Arguably more of a soil improver than a mulch. Wood cellulose is much tougher than plant cellulose, which means bacteria takes a lot longer to break wood cellulose down. While doing so the bacteria also breaks down nitrogen, if you spread fresh sawdust on a vegetable patch it will consume much of the soil’s nitrogen, thus making a poorer quality soil.
The only way to use sawdust as a mulch is to break it down until it is almost completely turned into compost before spreading it. A good way to do this is to first spread it on your paths and leave it there for a good 12 months. Once it has almost entirely broken down you can then spread it over your beds. But a WARNING, do not spread sawdust on your paths if you have couch grass in your garden beds. Couch grass loves to grow in soft soil, sawdust makes an ideal medium for couch runners to spread into. For more information about Couch grass see Removing Couch Grass.
Another problem with sawdust is that it has become much more expensive and harder to find, particularly hardwood sawdust. Though sometimes it can be obtained for nothing from larger horse stables as some of them use sawdust in place of straw as horse bedding. But whatever sawdust you source, make sure it does not contain any treated pine.
ABOVE: Sawdust (with some woodchip particles) on a pathway at the Ballarat community garden. BELOW: Couch grass spreading into that same pathway. Sawdust and Couch is not a good combination!
ADVANTAGES SUMMARY
ADVANTAGES
- Can double as a cover for paths.
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Is good for bulking up new soil.
DISADVANTAGES SUMMARY
DISADVANTAGES
- Takes a very long time to break down into a usable mulch.
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Not good as a cover for paths if Couch grass is present.
Lakeweed (only available in the local ballarat area)
Ballarat has a unique source of mulch in the form of lake weed that is harvested on a large scale from lake Wendouree during the warmer months. The harvest is dumped in Victoria Park next to Gillies Street South.
The benefit of lake weed to local gardeners is that it is free and contains no weed seeds. But as it is largely made up of water it contains few nutrients and quickly rots down to almost nothing. You can however sometimes find batches of it that have already rotted down, which means it is more concentrated.
While I have used lake weed in the past, because of its smell and the fact that it quickly rots down to almost nothing, I do not use it now.
Lake weed piled up next to Gillies Street, Ballarat. In the warmer months when the lake weed is being harvested gardeners can come and collect as much as they like anytime.
ADVANTAGES SUMMARY
ADVANTAGES
- Contains no weed seeds.
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Is free.
DISADVANTAGES SUMMARY
DISADVANTAGES
- Quickly rots down to almost nothing.
- Contains few nutrients.
- Smells while it is rotting down.
