How to choose a good peat free potting mix (or compost)

Mixing potting mix

If you've grown in a peat free potting mix  (or 'compost' as we call it in the UK), you may have found a significant variability in quality. In my experience, some perform superbly, many are fairly average, but poor quality is not uncommon either. In the UK, the sale of bagged peat products to amateur gardeners is to be banned from 2024. Peat is being phased out because its harvest releases large volumes of greenhouse gas, and damages precious wetland habitats. So it's important we all become more savvy about the different peat free options. Particularly, as the quality of a potting mix does makes a big difference to how well plants grow.  The fact that different potting mixes all look similar when in bags, makes it useful to know what we are looking for inside the bag. This is quite a long post. If you don't have the time (or the will!) to read it all, here is the essential info:

  • Peat free potting mixes are not all equal - and are made from a variety of different materials.
  • No one material is best, but coir and composted bark or woodchip based mixes tend to be more consistent and generally last well over several years. They are often more expensive but can be a good investment long term.
  • Green waste composts tend to be lumpier and more inconsistent. However, they can be good and are often low cost and made locally from sustainable materials.
  • The quality of the potting mix has a big impact  on how well plants grow. So it's worth doing a bit of research to find a good one that is easily available to you in your area.


What are peat free mixes made of?

Peat free mixes are not all the same. Most are made from one or other of three ingredients: coir (coconut fibre),  composted bark / wood chip, or green waste. Or sometimes a blend of all three.  There are also a few potting mixes that use completely different ingredients. Dalefoot compost, for example, is made from sheep's wool and bracken. But these are unusual - the vast majority are based on coir, wood chip or green waste.


Because these are ALL organic ingredients, they naturally vary from batch to batch. This is the principle reason why peat free products vary more in quality than peat based composts. (Peat is also a natural, organic ingredient but it is much more consistent).


What's the difference between these ingredients?

The common ingredients that peat free mixes are made of each have different pros and cons:

Coir

Coir or coconut fibre is a by-product of the coconut industry, usually shipped from India or Sri Lanka. It can make an excellent peat free compost. It drains well, holds water well, and rewets easily. It’s also available in neat, compressed ‘bricks’, that swell when reconstituted with water. This makes it ideal for those of us who need to carry our dirt up several flights of stairs. It has a pleasant smell and is nice to work with. In its raw form it is low in nutrients, and requires an added fertiliser to work as an effective potting mix. Most bagged coir mixes come with fertiliser pre-added. Some coir bricks come with added fertiliser, some require you to add fertiliser yourself. Check before you use. Coir is one of the more reliable and consistent (as long as it has fertiliser added) peat free ingredients. However, just occasionally can contain high levels of salt which are bad for plants. (I bought a batch about ten years ago that seed germinated very poorly in).

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Composted bark and wood chip

Composted bark is a by-product of the timber industry. Wood chip comes from a variety of sources, including hedge trimming, tree surgeons, and saw mills. They both hold air and drain well. They are also long lasting, retaining texture and structure well over several years. And they normally have a pleasant woody smell. Composted bark / wood chip tends to be more consistent than green waste (see below). But,  of course, there are lots of variables including what type of wood is used and how well it has been composted. Generally, though, it makes a good to excellent potting mix.


This is Sylvagrow compost which is a blend but mainly composted bark and woodchip. It's also nice to work with and lasts a long time. This is Sylvagrow compost which is a blend but mainly composted bark and woodchip. It's also nice to work with and lasts a long time.

Green waste compost

Green waste compost (or 'green compost' as it is now being branded) is made from park and domestic grass clippings, hedge prunings, and sometimes food waste. I wrote a blog post about it a way back, here. Because it is made all year round with whatever waste is available, the ingredients vary significantly from season to season. No grass clippings in winter, for example. For this reason, it tends to be more inconsistent than other peat free ingredients. It can sometimes have quite a pungent, unpleasant smell. Luckily, this doesn't necessarily affect how it performs. I once had a bag that was all clogged together and smelt terrible but the tomatoes grew great in it. Some green composts contain large lumps of wood. This can help improve drainage but may require sieving to make it suitable for sowing seeds in. Occasionally it can also contain bits of plastic and other contaminants. I once found a toy plastic gun in a bag of municipal compost! However, processes to remove unwanted materials are gradually improving. Despite its variability, green compost can still be made into a good potting mix, as long as their is good quality control. However, even when buying the same brand, it is prone to to vary quite a lot from batch to batch. So it can be more hit and miss - but is getting better. Green compost is often available at low cost from local councils / municipalities. Look for those that have the PAS 100 quality standard (this ensures it is tested for heavy metals and weed seeds). In my experience, municipal compost tends to be particularly variable. Sometimes it is good! I once helped out in a container garden run completely on municipal compost. And they grew good veg in it.  It's an option worth experimenting with, particularly for more experienced gardeners.


This is an example of green waste compost, made by the local council. As you can see it has large bits of wood on it - but it's still possible to grow in it. The more expensive brands that use green waste normally have far fewer of these large lumps. This is an example of green waste compost (rather wet as it had just rained), made by at my local council recycling facility. It has fairly large bits of twiggy wood in it - which is not untypical for the cheaper mixes based on green waste. It's not too bad for growing larger plants in - but benefits from sieving before seed sowing (and even then isn't that reliable for seeds). The higher quality brands that use green waste are normally less lumpy.

Which peat free potting mix to choose?

There isn't really one best choice for all situations. But here are some of things that it is useful to consider when choosing:-

Premium or budget brands?

The main differences between the more expensive and budget brands are quality and consistency. Premium brands invest more in procuring good ingredients and rigorously testing each batch. While this can never guarantee that every bag will perform superbly, it does significantly reduce the risk of a poor one. Cheaper brands - for example budget supermarket own brands - on the other hand, are prone to more variability, particularly those based on green waste compost (which most are). They can be good, but mediocre and poor quality bags are also not uncommon.  They are worth a go. But try to resist the temptation of buying lots of bags until you've tested one. I'd also try to stay clear of the budget brands if you are beginner. It's harder to spot poor quality compost - or to know how to manage it - until you have some experience. That said, if budget is the only option, don't be deterred from giving it a go.  Just bear in mind that if things don't grow well, it may be down to the compost and nothing to do with you. In general, though, a good quality potting mix is a good investment - and one of the best things to spend your gardening budget on.

Which can be re-used for longest?

Another consideration is how many years a potting mix will perform well for. I’ve been growing tomatoes in the same coir and composted bark composts for four years now. The composted bark has retained its structure better than the coir, but the tomatoes have grown well every year in both. I haven’t tested it to the same degree, but my observations suggests that green waste compost is more prone to losing its structure after a year or two. The good news, however, is that nearly all peat free composts perform much better than peat when comes to re-use. For longevity - and based on my observations so far - I'd recommend composted wood chip mixes first, followed by coir.

tomtoes in year old compost copy These tomatoes are growing in four year old compost wood chip (left) and four year old coir (right). The plant health and crop is still excellent.

Which is most sustainable?

As a bulky, heavy material, transport is the main environmental impact. The most sustainable option is to make your own compost. But most of us don't have the space for this, s0 what’s the next best option? Look for products sourced and made in your region or country. Locally made, green waste compost is often a sustainable choice - but you need to weigh that up with its inconsistency. Coir is often touted as a sustainable material - and it is a waste product. But it is also shipped long distance from India and Sri Lanka. Composted wood chip - as long as it isn't shipped long distance - is often a better choice. Alternatively, a good compromise is to reduce the amount of potting mix you need to buy each year. Choose a long lasting material - like composted bark or coir - and learn to reuse it each year. You could also learn to make your own worm compost to recycle your food waste - and help add fertility back into your compost each year.

Which is the lightest weight?

If weight is an issue, coir is a good choice, followed by composted bark. Avoid any mix with ‘added topsoil’ or loam as this adds significant weight. Perlite is often added to light weight mixes. It works well, but this needs to weighed against the fact that it is very energy intensive to make.

Which is the most pleasant to use?

Coir is perhaps the cleanest and most pleasant smelling material to work with. A good choice if you have to do your seed sowing on the kitchen table or near your favourite carpet! Composted wood chip is also nice to work with. Green waste compost can be more smelly and 'dirtier'. This isn't necessarily a problem, but it's worth bearing in mind before you lug it up the stairs.

Which brands are best?

The availability of different brands is very location specific, varying from country to country, even city to city. To find a good one you often need to ask experienced gardeners in your area, look for online reviews, or seek advice in a good independent garden centre. Two brands I've used and like - and that are quite widely available in the UK - are Sylvagrow and Fertile Fibre. Of course, there are other good ones, too.  Homebase and B&Q mixes often get good reviews, and Dalefoot have a strong following.  Also, check out the experience of other gardeners - around the world - in the helpful comments and posts on the Vertical Veg Facebook Page, Facebook Community and on Instagram. Elsewhere on the internet, Pumpkin Beth, did an interesting trial of different peat free compost here. If in doubt, try a bag or two - and compare a few different ones. You can learn a lot in the process - and hopefully find one you particularly like.

Your turn - what's your experience?

Are peat free potting mixes easy to get hold of and well labelled in the region / country where you live? What's your experience or growing with peat free compost? Have you tried any brands that have performed particularly well or poorly? Please share your thoughts in the comments so we can all learn from each other.


21 comments

Louise Jutsum
 

Hi. I agree with your observation that some local peat free composts have had bits of plastic in them although the Ace of Herts has improved over this. Also your observation on the high salt content in some coir based composts makes me feel that this could be an explanation for some mixed results I had earlier this year, Louise
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Ken
 

I use PASS green waste each year which I buy in a bulk bag along with a wooden pallet. I find the quality good and there have been no problem. I use the pallet for containing leaves and the bag is used as a planter.
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Alex
 

As this is my first year seriously trying to grow food, I've ended up trying a load of different composts, mostly unintentionally as I realised over the past few months that I would need more and more! I'm hoping to re-use a lot of what I've bought, and add feeds and things next year. Growing potatoes in a mixture of Sylvagrow and Miracle gro. Carrots in Miracle gro. Seedlings sown in either coir or Dalefoot. I like the coir and the Sylvagrow, so far i think they are producing the best results. The main problem I'm having at the moment is loads and loads of fungus gnats in all of the pots I'm keeping inside, I don't know if its a specific compost or whether its because i was storing the bags in the garden beforehand...
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Jane
 

It's really good that you're pointing us to peat-free composts - so important for UK peatlands to remain as undamaged as possible. I've become so worried about peat disturbance via horticulture that I think we shouldn't demand the possible perfection of any peat materials at all and should be prepared to have a few hiccups and disappointments, perhaps, for the sake of the planet... I found Horizon organic peat free very good for several years, though I've not tried with seed sowing, but it seems less available now in our area. Composted bark is a magic medium, wonderful for shrubs and borders, but increasingly difficult to find locally. It's interesting that you recommend for veg/seed growing as I wondered if possibly a bit too fibrous, but I would trust your judgment on it! Thanks for excellent advice on all this.
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Robin Stewart
 

The compost wich continues to perform well for me after after four annual re-invigorations since its purchase in 2018 is a mixture of Wilko multi-purpose compost and Durstons multi-purpose compost. Every year it is re-invigorated by addition of blood, fish and bone and overwinters in a re-purposed wheelie bin and successfully grows varied crops in my container garden back yard.
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Kerri
 

I splashed out on Fertile Fibre compost (a Which? Gardening best buy) this year having had disastrous germination with other peat free compost last year. It has been much better and worth the additional cost.
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Sally
 

I always bought New Horizon peat free in the past, but last year found it pretty awful. This year it doesn't look any better, though I haven't actually used it yet. I like Melcourt and wonder if Sylva Grow is better as it is more expensive.. Does Which? rate any others? Fertile Fibre does seem rather on the expensive side.
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Mark Ridsdill Smith
 

Hi Sally, yes New Horizon can be good, but you are not the first to mention how variable it can also be. In the Which? trial this ear, YouGarden, Sylvagrow and Moorland Gold came top. Of the high street brands, Homebase does quite well, followed by B&Q.
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Mark Ridsdill Smith
 

So glad you are having a good experience with your compost choice this year - it's so demoralising when you get a bad batch that is hard to grow in.
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Mark Ridsdill Smith
 

I'm so glad to hear that you are using green waste successfully, that's excellent news - thank you for sharing Ken. Do you mind me asking which city or region you get it from? Also, if you re-use it each year or if you start afresh?
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Mark Ridsdill Smith
 

Sorry to hear you had mixed results earlier this year Louise. I haven't used coir enough to know how common it is to get a batch that is unbalanced and difficult to grow in - so far I've had had one poor batch and three very good ones. Haha, Ace of Herts is fun, original name for a compost brand!
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Mark Ridsdill Smith
 

Thanks for sharing this Jane - and, you are right, we can't expect perfection from our peat free composts. It's extremely challenging to make, particularly in the large and increasing quantities there is suddenly demand for. As you've noticed, I wonder if composted bark is in shorter supply these days - at least I think Sylvagrow used to have a higher percentage of composted bark but now contains more composted wood chip. It does seem that, as long as composted bark is sifted fine enough and composted properly, that it can be good for seed germination. I think some farmers are now making their own propagating compost from wood chip from their hedge trimmings.
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Mark Ridsdill Smith
 

Hi Alex, yes, I identify with buying lots of different composts, I did a very similar thing when I started out. It can be a very good way of learning - and interesting to observe how the plants grow in different ones (although it's easy to forget which is which unless they are labelled!). Sorry to hear you have fungus gnats. Unfortunately they are very common (I have some too this year) and one reason why I try to minimise the amount of growing I do inside.
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Susan Hunt
 

Hi Mark, I sowed all my veg from tomatoes and cucumbers to sweet corn and melon and loads in between. They were raised in seed compost from our local nursery, which I use every year. I had almost 100% germination. I potted them up in peat free compost, super grow, from Homebase and most have died! I checked the internet and many people have had similar experiences with it. I have resown everything and again it’s all germinating well. I am going to pot it up in Leveringtons compost, bought from the nursery. I just hope this works because I’m running out of time and seeds now. Happy growing to everyone and thank you Mark for a brilliant web site, so glad I found it.
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Alex
 

Thanks for the reply! Haha yes i'm sure i'll have forgotten by next year! The coir at least looks different to the rest. I was a bit sniffy about the miracle gro as it was cheap but the carrots i planted in it have germinated now, exciting! Interesting that you said that you can get compost from the council where you live - i have looked everywhere on my councils website (vale of Glamorgan) and no such service seems to exist - will have to email them and ask about it
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Susan
 

Hi Although I have a sizeable garden and would love to dig out some of the garden and plant some vegetables but if I give the horsetail weed an inch.....it takes a mile. My whole garden is riddled with it and I've battled trying to get rid of it for 20 years with ZERO success and tried Many things to kill it but nothing works. Ive given up the battle but having said that I have grown several vegies in containers like spinnach, spring onions and carrots etc. Our local council in Stirling has a constant compost heap at our "Waste Management Service" and any stirling resident can help themselves to any amount of compost. It is quite woody though. I think it's quite good for my containers but I'd never put it into my flower bed or garden shrubbery because I think it contains a lot of weed seeds. I guess I can't complain as I get it for free. I'm now trying to make my own compost.
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Mark Ridsdill Smith
 

yes, availability of council compost does vary quite a bit. And in some areas there are other enterprises making green waste compost or similar. Here in Newcastle there is both council made green waste and a company called Green Leaf that makes a similar product. It's normally pretty low cost, particularly if you have space for a whole dumpy bag of it (which most of us don't).
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Tricia
 

I have used Harmony compost this year and it’s performed really well for all veg and flower seedlings. No longer use New Horizon, quality has been unacceptably variable and I’ve frequently had poor results, seeds not germinating and seedlings failing to thrive. I like to mix up my own compost for tomatoes and courgettes using home made garden compost, loam/topsoil, leaf mould and adding (sterilised) crushed eggshells, vermiculite, Epsom salts and fish blood and bone. The plants love it. Great recipe from Project Diaries on YouTube! I’ve had enormous problems with fungus gnats and successfully used a product comprising a sticky yellow card which attracts the gnats and breaks the reproduction cycle. We have a fantastic social enterprise company in Sheffield called Green Waste which makes PASS compost, bit woody but good soil improver.
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Mark Ridsdill Smith
 

Thanks for sharing all this great info, Tricia. Harmony compost is new to me - I'll look out of it. Fungus gnats are a complete nuisance! I've got them, too, and keen to get plants outside ASAP. Your tomato and courgette mix sounds a good one :) Thanks!
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Martin
 

I have a rooftop container garden and I'm also lucky to have a garden with several trees which feed my compost bin. 

Grass clippings, kitchen scraps with some cooked food and dead leaves with the addition of large quantities of coffee grounds and eggshells  from the hotel cafeteria where I work. I also have friends with rabbits and they give me bags of droppings and straw mixed with urine. All good stuff! 

My compost heats as much as 60°C and decomposes fast. I mix the compost with up to 20%-50% perlite and/or vermiculite and coir to get a lightweight mix and so far I'm satisfied with the results. 

I always add a new layer of homemade compost with each new round of lettuce planting. 

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Mark Ridsdill Smith
Staff
 

Sounds like a great system you have Martin, making the most of what is available to you in your area. Perfect. 

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