Peat free compost: why to use and which to buy

An avid gardener road-tests two brands of peat free compost, and gives you a recipe to make your own

Last winter I found myself out in the garden on most evenings, checking the bird feed and ensuring that they had a trough of unfrozen water. This spring, like every other, I have resisted using slug pellets despite watching lettuce after lettuce disappear in a frenzied orgy to rival any Roman feast. I also make insect hotels and whenever possible I leave areas of my allotment wild. I would like to call myself a wildlife friendly gardener. But alas, I feel that it is about time I owned up to a dark secret.

I have on more than one lazy occasion, used compost with peat in it.

My reasons were simple: it had organic written on the packet and therefore I turned a blind eye to the fact this it did not say 'Peat free'. Also my local shopkeeper only sells compost with peat in it and I would have to walk a 3 mile round trip instead of a 300m one in order to buy some from the local garden centre.

This year I have vowed to change all this and so far I have stuck to it. But what is peat, why go peat free, what difference does it make if gardeners stop using peat and are the alternatives any better?

Why do gardeners use peat?

When plants that grow in swampy areas die, they do not decompose properly. Instead they turn into a partially rotted organic material; a material know as peat. Many multi purpose composts contain peat as it can help retain water. It is for this reason that some gardeners will also bulk-buy peat in order to add to raised beds so they stay moist.

It is noteworthy that if your shop bought compost does not say that it is peat free then there is a strong chance that it does indeed contain peat.

Why go peat free?

There are many reasons for not using peat; firstly, peat renews at approximately 1mm per year, therefore it is considered a non-renewable resource. Secondly, peat bogs store carbon, a lot of carbon. In fact the equivalent of 20 years of industrial carbon is stored in British peat bogs alone. The more that this erodes, the more carbon is released into the atmosphere. What's more, exposed areas can dry out, thus releasing carbon even when not harvested.

Thirdly, peat bogs are home to a huge array of flora and fauna that thrive in such conditions. This includes birds, such as snipe and the skylark, which breed on peat bogs, as do many butterflies and dragonflies.

Although some peat is used as fuel, the vast majority of it is used by gardeners. It seems in our attempt to create our own little wilderness that we are selfishly robbing another.

Putting peat free compost to the test

I understand that it could be a bit of jump from using peat to using peat free therefore I decided to 'road test' some different types of peat free compost to see if they did the job properly. Bearing in mind that a whole host of people read the Ecologist, I used two very different sources of compost namely Petersfield and New Horizon.

Petersfield are really the Rolls Royce of the composting world, supplying such prestigious customers as the Queen, The National Trust and Kew Gardens. They do supply the common man but load sizes start at 10 pallets worth! New Horizons on the other hand supply many garden centres and even have stock available online.

The first test was the look and smell of the composts. Both had that rich composty smell that you expect and neither were at all rancid. Also both were very fine and did not have lots of bits of bark or other un-composted material in them. This can be a problem with some if not all of the cheaper composts (including those that contain peat). As with most products you get what you pay for: a bag of cheap compost is a false economy, since whatever you grow in it is not going to grow as well as it would in the more expensive composts. This means that you will grow less produce and in turn save less money on your grocery bills.

The second test was for germination results. Having my gardening diary handy, I could in effect pit the Petersfield and New Horizon composts against last years results, checking the results of my own strain of sweetcorn and a shop bought courgette seed. Last year I bought a cheap organic compost containing peat from the local green grocer and I planted exactly the same seeds. The germination rate was poor at about 50 per cent. This year the two mediums performed very well indeed at around 90 per cent each. Which does prove the false economy point - it also shows that a good peat-free compost is better than a bad one made with peat!

Making your own

If you want a free option then you will have to have patience but the final option is perhaps the most ecological of all - making your own potting compost from leafmould.

As organic gardening pioneer and founder of Garden Organic, Lawrence D Hills suggests writing back in 1977, 'peat is an expensive substitute for leaf mould....[which], with enough time to decay, could serve all the same purposes'.

Therefore an annual trip to the park with a collection of bin bags could be in order! If your local parks are like my local park then the leaves are blown into a pile using a leaf blower and then simply burned. It is the same on many golf courses and on other big estates, so if your park is not an option do ask the owners of these places if you can have their leaves. I would advise against going to a local woodland to collect leaves for leafmould as you may interfere with the natural ecological cycle of that area. Which would, again, defeat the object.

For those that have never made their own leafmould it is quite simple, first fill a bin bag full of autumn leaves. You then have two options: either pierce the bag with holes and wet the leaves and leave for two years. Or option two:

  • run a push mower over the leaves (to speed up decomposition);
  • put four posts into the ground at approximately 1.5 m apart and attach some chicken wire to the posts;
  • fill with the leaves, ensuring that they never dry out.

The easy bin bag method can take up to two years to obtain a good result, but the chicken wire method can be much quicker at just six months. At the end of this period you will have an ideal multi purpose compost to rival any peat compost.

Andy Hamilton is co-author of The Selfsufficient-ish Bible (£20, Hodder & Stoughton)

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