Peat free compost trials 2021

Over the last 7 – 8 years I’ve only used peat free compost after I switched and found my plants grew exactly the same or better in peat free compared to peat. In that time I have grown thousands of plants from seed as well as permanently in large pots. If the bag doesn’t clearly say ‘peat free’ it will contain peat dug from natural habitats. Digging peat reduces habitat for wildlife and releases millennia of carbon locked into peat bogs, which then converts into climate warming CO2.

This year I’m growing everything in peat free compost as usual and I’ve been given one bag of peat to use in a series of comparison trials. I was also given bags of Dalefoot, Fertile Fibre and Sylvagrow I’ll feature here – though I’ve bought and used them for years – to trial but I’m under no obligation to say they’re good, and here you’ll see for yourself how they all perform. I will be running separate articles on each of these in the future.

This is my personal account based on how I grow, I’m being fairly scientific about it but with more resources and time, someone could conduct larger trials with multiple plants. Over time and with a number of comparisons and insights into my techniques, I hope to show you how I grow with peat free composts and why they’re such a great growing media.

I encourage you to try the same, choose the same plant to grow in different composts but in the same way, for a fair comparison.

The secret with peat free composts

One of the issues I’ve seen online is when people grow something in peat free compost and it fails, the compost is blamed. When actually, there are loads of other variables that could have caused the plant to fail such as:

  • under or over watering
  • too low or too high temperature
  • too little or too much fertiliser
  • too little or too much light
  • a bad batch of seeds
  • pests
  • disease
  • a combination of these
  • something else entirely

Yet my experience is that I’ve never had a crop fail or perform badly because of the compost, whatever it is or whatever consistency or quality. That would also apply to peat composts. I’ve had crops fail of course, but for the other reasons above. One year I thought a bag of New Horizon peat free had weed killer in as seedlings suddenly became stunted. But a week later they started growing again and, looking at data from our weather station, the weird growth happened in the same days as an unexpected late cold snap in the weather.

It’s about understanding the growing medium. Peat compost varies in nutrients between product and batches as much as peat free because peat is naturally devoid of nutrient value and has to have everything added. Home made compost and peat free composts can vary too, sometimes with low natural immediate nutrient. Compost manufacturers try to compensate for this by adding natural or synthetic fertlisers.

Different composts will have different water retentiveness too. Peat free compost on the whole tends to be very water retentive. But it can be misleading because the top dries out faster than the rest. So with peat free compost if you aren’t checking further down, it is very easy to mistakenly overwater – something I learnt by it happening to me. I overwatered, thought there was a problem with the compost, but there wasn’t, as I found out when I tipped out the sodden plug plants.

Some people use pure coir which doesn’t retain water well, it dries out quickly and contains no nutrient value whatsoever. Coir should only be used for starting larger seed and cuttings before quickly potting on, or as part of a mix of different compost materials.

Because peat free composts can sometimes have different nutrient contents to what people are used to with peat, I tend to start adding fertiliser earlier to seedlings’ water every fortnight at half strength. It changes depending on the species of plant but generally once they’ve one or two sets of true leaves and are visibly growing strongly, I start giving the weak fertiliser. Too early and the rich fertiliser can burn delicate roots.

Using peat free is about learning to use compost again and being more aware of plant needs, it’s not hard and once you get used to it, like me, you will find that it is better than peat. Peat dries out faster and gives you less control over the nutrient content.

Structure and texture

In reality there is very little difference between any of them. But to go into painstaking detail…

Of the five multipurpose composts I’m trialing, the peat is noticeably the finest, which may seem like a good thing but I totally disagree. I prefer growing media to be structured with small and large bits, allowing roots and water to move easily between compost, through the air spaces.

What I don’t like about super fine sand-sized composts is that over the time the structure can solidify. This is why I never intentionally use seed compost anymore, too often the tiny air gaps collapse and the seedlings struggle to send out roots.

Worse is for longterm pot plantings of say 2 – 5 years where I find fine composts can – not always – compact, clogging drainage. Peat free composts of mixed size, especially with bark do decompose over time and sink, compacting slightly, but keep their open airy structure for many years.

Sylvagrow Organic has the next finest with a good mix of different size pieces, but there are very few large pieces of twig etc. So it feels a balanced mix. New Horizon and Dalefoot have a similar consistency with a mix of sizes including the odd larger bit of twig or bark. Something I consider to be a good thing. Easily removed by hand in seedling pots.

To be fair to Dalefoot, they also offer a seedling compost with a finer consistency to their multipurpose, something they recommend for seedlings. Using regular multipurpose is my preference, which is what I’m trialling here – you have both options.

Overall, I much prefer the structure of the peat free composts for both seedlings and long term plantings. I would never use such a fine compost as the peat has in long-term plantings anymore, which is also why I avoid John Innes formulas (in addition to avoiding its peat and soil content – I use soil, but from my own garden).

Round one: wild rocket

8 June 2021 (sown 27th April)
17th June

I asked my readers what crops / plants you’d like me to trial and something that came up from a number of you is anything with small seeds. For some reason the gardening world has convinced itself that tiny seeds need fine compost to germinate, which is wrong, so in the first trial I am growing wild rocket with its small seeds. It’s also a fast growing leafy crop, needing reasonable amounts of nutrition.

This is one of two trials for long-term results in pots alongside the cosmos below. I’ll keep both of these growing in pots of compost to see how they grow in each compost long-term. As I would normally, I am adding liquid seaweed fertiliser every fortnight or so to these plants after 4 – 6 weeks of growing without it.

Each plant received equal amounts of liquid fertiliser but I adjust the amount of water depending on the retention of the compost – one of the key techniques for using any compost, you have to know how much to water.

I sowed them on 27th April, covering ever so slightly with a dusting of compost from each and watering gently from underneath. The pots are in my unheated polytunnel.

A little over a month later and they’re all growing strongly, some germinated later – the peat and Dalefoot accounting for the slightly smaller plants, which isn’t a problem as they’re catching up fast. Both of these composts are very water retentive, which means it was likely colder in the cold May we had this year, the reason for the slower germination.

Round two: Cosmos ‘Purity’

Again, the peat and Dalefoot are off to a slower start but still growing very strongly – so I’m not concerned about either.

The Dalefoot, New Horizon and Peat retain water the most, so I can’t water them all the same amount – giving these less.

Here they are a few weeks on and they’ve all caught up with one another – I snapped a branch off of the Sylvagrow plant by accident. At this point I had to abandon this trial because I ran out of larger pots and the plants were so rootbound it started to affect all of their growth! Interestingly, as they became more rootbound, the growing points distorted slightly on every single one. In the end I have planted them all out into the ground and I will revisit this trial next year with larger pots.

This is probably the more interesting of the trials I’m conducting as I’m going to keep the cosmos in the pots rather than planting out. I’m giving a fortnightly seaweed feed now to all of them as I would do normally with plants.

Round three: courgette ‘Gold Rush’

8 June 2021

Round four: Squash ‘Orange Hokkaido’

8 June 2021

Round five: Squash ‘Musquee de Provence’

I sowed some seed of Squash ‘Musquee de Provence’ which I had from last year. The seeds in peat and Sylvagrow didn’t germinate because the seed was no longer viable, nothing to do with the composts. As you can see, the three that did germinate are growing fine.

Round six: Mustard ‘Purple Frills’

All five mustards are growing in exactly the same way as one another – the root systems are the same too. All looking strong and healthy and ready to go out into the ground.

Round seven: French bean ‘Cobra’

All plants growing in exactly the same way, strong and healthy with good root systems and ready to go outside. The Sylvagrow plant has a bit of insect damage to its newest leaf accounting for the different shape, but that doesn’t affect growth at all.

Keep coming back to this page for updates and more rounds from different crops!

General observations from using peat free compost

I only use peat free composts, so as well as the comparison trials, I can show you all of my other plants as they grow.

Sylvagrow (Organic Peat Free)

I really like the consistency of this compost, all a consistent mix of different sizes, retains water well and seems to have a good amount of nutrition within it – which is great for a completely organic compost. Everything develops strong roots in it.

9 varieties of tomatoes, off like rockets and very healthy. Didn’t have any additional fertiliser at this point.
5 different varieties of chillies (and some tomatoes at the back) growing very healthily – one liquid sea weed feed at this point
23rd March – multiple different types of salad plants germinating happily
4th April – full germination, many true leaves growing, healthy without any additional fertiliser yet (I didn’t add any before planting out).

New Horizon

This is the most widely available peat free compost and therefore the one I have used the most over the years. I find it consistently good and everything grows well in it – short or long-term.

I used New Horizon in this tray using a soil blocker to make squares of compost to plant into.
Here you can see the root development in one plant – the compost develops a white dusting on the top surface which makes it tricky to judge water retention but it has no effect on the plants.

Dalefoot

Dalefoot is a particularly good compost and the company restores natural habitats and peat bogs off the back of its sales, so you purchase is contributing to habitat restoration. I’ve used Dalefoot a lot over the years and it’s consistantly good, though this year I found the mix a little off with some clumps that needed breaking apart. This caused a few problems in the first few weeks with a dry ‘crust’ on top of the the trays which could inhibit germination. However this was remedied by breaking them apart and regular wetting of the surface. Generally though Dalefoot is usually finer in its texture and I always recommend it.

Kohlrabi roots growing strongly in Dalefoot
The brassicas develop excellent root structures in this compost!
Nasturtium and Leonurus sibirica growing well

15 thoughts on “Peat free compost trials 2021

  1. Really interested to see the outcome of this. I’ve used the Westland for the previous few years and felt the consistency has definitely improved (used to get bags with big big chunky bits, definitely didn’t feel like compost to me) in the last couple of years, was nice to use last year. Have recently switched to the Sylvagrow as it’s what our allotment association stocks and my lottie neighbor recommended it. So far so good, but interesting your comment about the watering as I’d felt it was definitely not retaining water as well…however, I’m going to make a double check from now on in case I’m over watering as the top often looks very dry! Great tip, thanks! 🙂

  2. nice one Jack, I’m curious to see how this pans out. I’ve been trying different varieties too, and with such differing price points, it’s good to have a 2nd opinion as to which one performs best. I do like the Dalefoot compost, so might try a trial between that and Aldi’s peat free, which was 1/2 the price.
    cheers

  3. Thanks so much, your research and information has now given me the confidence to switch. I am still finding it hard to source pear free and understand that this is due to the huge industry involved in the manufacturing of compost. By sourcing one of the you have used my enjoyment of horticulture and gardening will fully return. Stay safe Bill

  4. Really great article, Jack – thank you so much for doing all the thorough, detailed growing and research that I meant to, and reporting on it so carefully! You’ve crystallized a number of things I’d noticed this year, but not got into words inside my head (water retention, use for small seeds, different-sized bits being a good thing, and others). Thank you!

  5. Jack: Thanks for sharing these results. I am trying to start a grass-roots campaign here in the U.S. where there is essentially no awareness of the peat issue. Canada has enormous reserves of peat, it’s a mega-business, and there are very few peat-free options. I am currently running a trial of 4 peat-based growing mixes and 16 (hard to find) peat-free options. Our climate in Arizona is much too extreme to try to grow anything from seed (in July). Instead, I am using small plugs of vinca, which grows wonderfully in spite of the heat. (We had 10 days in a row in June with temperatures over 43 degrees!). I have subscribed to your newsletter so I can stay abreast of your trials. Thanks so much for helping us here in the U.S.!

    1. Thanks Maurice – for the message and for joining my newsletter 🙂 Good luck with your own trials. It’s great that you are starting with vinca. I have quickly found that it is more important to prove to people that peat free can work for long term pot planting. Especially in the case of nurseries who are selling plants that may be in pots for many more months than we would normally have them at home, and they need to look good for sale.

      So far I’ve found it makes no difference which compost I’ve used for growing seedlings that then get planted out. So I think you are on the right track already.

      Jack

    2. Oh, I’ve just realised, you will likely find that your subscription to the newsletter hasn’t worked because it is only technically available to people within the UK. Due to very dull tax reasons and the cost implications of that. One day I hope to open it up to every country around the world.
      Jack

  6. Great overview of the peat free options. I bought a bag or New Horizon recently and was surprised how much pearlite was in the mix, you can hear it crunch when i stick a scoop in the bag. This seems a visually different mix to what I have seen here and on other photos of New Horizon. So far it seems ok and I can only guess the pearlite is there to hold more water. Anyone had the same experience?

    1. Hi Lee, that’s interesting because I’ve never seen perlite in New Horizon. Perhaps it’s a new ingredient? I wouldn’t personally want perlite in compost.
      Jack

  7. I wonder if you’ve had a problem with fungus gnats with any of these? We reported our houseplants in peat free bought from garden centres and were plagued. Managed to solve the problem by switching to coir.

    1. I’ve had fungus gnats one year and used sticky traps to deal with them – though they aren’t a problem unique to peat free. Fungus gnats have been a problem of peat based composts before peat free compost was discussed 20 years ago. Fungus gnats can be found in any compost.
      Jack

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