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Gardening Which? compost trials


Greenhouse plantlets

Greenhouse plantlets

I was fascinated to read and see the results of Gardening Which? compost trials in this month’s magazine. The results are extraordinary and in many ways disappointing. The peat free compost just doesn’t cut the mustard – at best achieving 54% compared to the best buy 88% for seed sowing. Young plants did even worse 46% compared to 92%. Up until now I’ve tended not to buy the cheaper compost and was under the misapprehension that more expensive compost was better and would give my seedlings a better chance.

Last year I noted that Sarah Raven uses jiffy7s or multipurpose compost for seed sowing. Up until then I had always used seed sowing compost for raising seeds and switched to multipurpose compost – much cheaper and giving good results.

The Which? trials confirm this on the multipurpose compost front. Their best buy is B&Q Multipurpose compost for seed and young plants, they note,
“After six weeks without additional feed, this compost produced plants of exceptional quality and consistency.”
At £4.28 for 70 litres it was also the cheapest compost on trial. Score 88% on seed sowing 92% for young plants. The B&Q Sowing and Cutting compost had the same score for seed sowing (88%) but not so good for young plants (88%). Incidentally B&Q multipurpose compost won best buy in 2009 as well. Unfortunately the winners were not peat free.

The best peat free composts were New Horizon Organic and peat free growbag for seed sowing (54%) and New Horizon Multi-Purpose compost for growing on small plants (46%). The six “Don’t Buy” composts were all peat free with one just scoring a shocking 4% for growing on young plants!

Over the last ten years the proportion of peat used in growing media and soil improvers has dropped from 70% to 46% but the increased popularity of gardening has boosted the demand for compost so peat bogs are still at very much at risk.

The low scores of the peat free composts are depressing. Various companies are experimenting with natural additions to counteract the loss of peat and hopefully sometime soon these will be widely available.

Meanwhile I’m going to try the New Horizon composts and experiment from compost made entirely from grass cuttings and leaves which gave me surprisingly good results for seed sowing last year.

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  1. John Walker

    Interesting to read the comments here. I’d also give a thumbs up to New Horizon compost, which has been a consistently good performer in my trials of all the main peat-free brands.

    If anyone is interested in reading more, I’ve a 4-page article in the May 2012 issue of Kitchen Garden magazine (out now) in which I share some of my results and offer advice for anyone switching to peat-free gardening.

    There’s also more information online. This page of my website has the appropriate links:

  2. Heather E

    When I read Fiona’s blog I rubbed my hands with glee – I have a B&Q voucher languishing in a drawer, and thought Yippee, I’ll get myself a real bargain and have some wonderfully sturdy plants into the bargain.

    Then I read the later comments re: peat -v- non-peat. What’s a girl to do? Bargain -v- Conscience. Tough cookie, this one.

  3. From what I understand the Which trial was not about the peat conservation issue, merely about which medium raised the better plants.

    Linda, I think you’re quite right, and I think that’s part of my problem with Which?.

    My father subscribes and is always telling me that, for instance, Which? says Fairy washing-up liquid performs better than Ecover. That might well be true, but I’ve already decided I’m not buying Fairy for several reasons. What I want to know is which eco-friendly washing-up liquid not owned by P & G is the best.
    Which? are only doing what it says on their cover, so it’s my problem not theirs, but I do wish they’d take other aspects of purchasing into consideration, especially as being environmentally friendly is not the niche in society it was a few years ago.

  4. Magic Cochin

    I’ve bought peat-free compost for the past 10 years and the New Horizon Compost is definitely the best IMO.

    For sowing and seedlings I mix with either vermiculite or pearlite which I buy in a huge sack (so much better value than those teeny bags). Not sure which of these I prefer – possibly the pearlite.

    For larger plants I use my home-made compost or a mix of home-made and New Horizon.


  5. I have been growing from seed for about 30 years, and found out very early on that peat in bag compost made a huge difference. Even within the last few years I have continued to try the odd bag of peat-free, and have still found that it performs poorly. I mix 50/50 homemade for potting on larger plants, but have found that using only homemade for seeds produced too much weed, because our heaps are not hot enough to kill weed seed off.
    From what I understand the Which trial was not about the peat conservation issue, merely about which medium raised the better plants. I totally agree with them – tiny plants are sturdier, stockier and healthier. It gives a much better start in life!

  6. Jenny Debeaux

    Which? magazine can help save money – and I’m without a job and have a pretty minuscule pension, so I know a bit about that – but sometimes it’s best to spend a bit more.

    I’ve not had any problems with using peat free compost, either for sowing seed or raising plants, and, in fact, the results have been very good indeed. I don’t want to use peat and I know I can grow stuff well without it.

    On another note, I stopped my subscription to Which? when I found I was disagreeing with their findings. Sometimes buying the cheapest really isn’t the best!

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