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Peat or peat-free growing medium?

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Jim McColl Jim McColl | 08:44 UK time, Wednesday, 26 January 2011

The idea that we might coin the phrase 'growing medium' where previously we used the word compost seems to be catching on. I for one try to use it to avoid confusion.

Actually, there is much confusion at the moment with quotes in a range of publications about the big theme of the day: peat-free growing medium. We have come a long way since gardeners were first encouraged to give up using peat but in my view, we still haven't got there yet.

Beechgrove peat-free trial with geraniums

Last year at Beechgrove we conducted a peat-free compost trial using seedling geraniums. This picture illustrates the variability of peat-free products.

I was in at the start, interviewing for television, a professional environmentalist and therefore a strong supporter of the idea. We were standing on the Red Moss, outside Currie south of Edinburgh, one of the last lowland raised bogs (LRB) in the country, which is still intact. As many will know, it was areas of LRB across the UK, which were 'mined' for the right kind of peat to satisfy the need for a new growing medium. It is a unique geological formation and supports a diverse ecosystem all of its own. We've had debates and seminars on the subject and despite the need for change, I remain a sceptic regarding the way the debate has been treated. Politicians need deadlines to suit their vote-grabbing policies but dressed-up to appeal to people's consciences about the planet, carbon footprints, global warming, and climate change - have I missed anything out? Oh yes - biodiversity! They have a 'tick box' mentality. The incongruity of it all is that some authorities claim peat reserves across the globe are growing faster than we can use the stuff and perversely, power stations are still being built to be fired using peat! Joe Bloggs asks "wot's goin' on, I'm a bit confused mate?"

I hope you can see what I mean and whilst the scientists and manufacturers are still trying their level best to produce a substitute that is CONSISTENT and REPEATABLE, let us use a pragmatic approach. Whilst we experiment to find the right alternatives, a process that requires significant research and costs money, let us continue to use peat from bogs where, if you like, the damage has already been done and certainly ring fence raised lowland bogs in this country that are still untouched. Incidentally the rules for repairing bogs that have been worked out in the UK and Ireland are pretty stringent. Some of the results in this phase are quite stunning.

Where do I now stand in this debate? It must be pretty clear by now but since day one I have advised that using peat for soil amelioration is a grave misuse of a valuable material. Positive results of this action are likely to be transient and therefore it is to be deplored.

The trouble is, peat is such a good, reliable material. What age is peat? The answer is measured in thousands of years. As a result, it is chemically inert when used for our purpose, it is also free from harmful organisms. Together with its water holding capacity and air exchange properties, peat remains the number one material in the right price bracket to be used as a growing medium.

What age are the alternatives containing composted green waste, wood fibre, bark, paper etc.? This will vary significantly from one recipe to the next but they are all likely to be well under 100 years old and these materials are likely to be chemically ACTIVE under certain temperature and moisture regimes and therein lies the problem. In one recent report, the same product varied from bag to bag let alone from one sales site to another!

Truth to tell, for seed sowing, cuttings and young plants, I will still recommend peat -based growing medium and that view is endorsed by the recent Gardening Which report. Older plants are more likely to be able to cope with the best of the peat-free range.


  • Comment number 1.

    I have been using New Horizon peat free organic compost from their grow bags to sow seed in for three years now. I have successfully sown and grown on a wide range of veges (tomatoes, chillies, herbs, peas, beans, squash, broccoli, salads) annuals and perennials, and wouldn't dream of resorting to a peat-based growing medium. I can understand professional growers feeling they need peat-based products to grow on, but am convinced that any amateur gardener can get perfectly adequate results from using peat free products provided they pick quality examples of these.


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