This is another reason why I don’t like using compost containing recycled green waste, the weed seeds and liverworts that develop within days of being transferred out of a bag, into a pot and exposed to the light. The high temperatures achieved composting on an industrial scale is reckoned to kill these seeds but the evidence suggests otherwise.

Echinaceas potted on a week ago into cheap peat free compost containing recycled green waste

If you leave them, in a couple of weeks it gets worse.

Three weeks after potting on these astrantias, the weed seeds and liverworts have taken hold.

I never get this problem with peat based products and it is evidence that the manufacturers have still got a long way to go to produce viable  peat free alternatives.

For the last three years or so, I have gradually begun thinking more carefully about the seed and potting composts I use. This has partly been caused by a stirring of conscience due to what I have read in the peat-v-peat free debate which has appeared regularly in the popular gardening press, but also because of some poor results which I am now putting down more and more to the compost I use and not just my poor plant husbandry. I purchase quite a lot of compost each year, probably 20 bags or more (1000+ litres), and so I have tended to buy cheaply at Garden Centres and DIY stores. Three bags of multi-purpose for £10 – £12 has been the norm. However, I now believe this may have been false economy and when it comes to potting compost, it seems to me you definitely get what you pay for.

I subscribe to Which? Gardening and when they  publish the results of trials, the ‘Best Buy’ products are usually heavily promoted by the manufacturers and become good sellers with such a ringing endorsement. However, they only seem to test the big brands and therefore the results might not actually reflect the best products at all. Nowhere is this more true than with compost. Of course, if you only ever go to the big chain garden centres and DIY sheds you will only buy what is on offer, and that is normally the major brands with whom they have exclusive arrangements. But, if you cast your net wider to the nurseries and smaller independent garden centres, I believe there could be better alternatives. These may only be available locally or regionally, but it may be worth seeking them out rather than sticking to the ‘safe’ major brands. That is what I have done recently and I think the results are beginning to show. I have nothing in particular against any of the big brands or their products but I have tried most of them and only one, J. Arthur Bowers, has been consistently good. In virtually all the others either the consistency and moisture content has been poor or I have found foreign objects, large pieces of glass, wood, plastic and stone which can only mean one thing, poor quality control. However, I accept that many customers are totally happy with B&Q, Homebase, Westland, New Horizon, Levington, Miracle-Gro and many other popular brands and my experience may not be typical, but I would also argue that many customers simply accept shortcomings without complaint or don’t know the difference.

The best bag of potting compost I have used this year by far has been a “professional growing media” as the trade call it, which I managed to buy from a local nursery owner who admitted to me that she couldn’t afford the risk of using a poor compost and needed better ingredients and better nutrient levels to grow decent plants for sale. She let me have 3 bags for £7.50 each. It is sold by the pallet load of 40 plain white bags and is a beautiful consistency, about 75% sphagnum moss peat and 25% sterilised loam with added nutrients which apparently last for up to 3 months. So why might the quality be less good in the popular multi-purpose brands? I suspect it would simply be too expensive to mass-produce any better and you wouldn’t be able to buy three bags for £10 – £12 which is what the average garden centre or DIY store customer (like me) expects to pay.This year, I noticed a proliferation of more expensive composts with added water retaining granules, or ‘enriched’ with John Innes or organic nutrients making an appearance, but I think this is just window dressing. The real value is in the basic ingredients of the compost itself. Which brings me nicely on to peat-free composts.

There is a popular nursery not far from me which proudly boasts it’s peat free credentials. I went there recently with the intention of buying certain plants but came away with nothing. I was dismayed at the poor quality of the stock, the weed seeds which had germinated in the pots, the mosses and liverworts on the compost and the general pallor of plants for sale at full prices. I managed to inspect an open bag of the compost they use which seemed to be wood fibre and recycled green waste. It was dark and claggy and far too wet. When I squeezed a handful it stayed compressed and didn’t spring back and crumble like a peat based product would have. It didn’t take much imagination to guess where the weeds and liverworts came from. Numerous tests by very clever people have shown that these peat free products are still not as good as peat based. However, things are slowly but surely improving. I was informed by a nurseryman last week that he now uses a peat free compost which he mixes with some John Innes No.2, Osmocote granules and 6mm grit for all his seed sowing and potting-on. The manufacturer is W E Hewitt & Son in Leicester and it is marketed as Petersfield Peat Free Supreme but again, it is only available in bulk and is comparatively expensive.

On my journey to find Petersfield composts I stumbled across a small manufacturer in Hereford called Carrs Special Organic Products.This turned out to be an innovative farmer who composts his cattle manure with worms, harvests the wormcasts and mixes them 50/50 with Irish moss peat, grit and added nutrients to produce a beautiful potting mix with a wonderful silky consistency. It was developed in conjunction with Pershore College of Horticulture so it has been fully tested and is of proven quality. It is as expensive as all the other ‘specialist’ composts at £7.49 a bag but this seems to be the benchmark cost, about twice the price of the “3 for £12” brigade, but I have come to the conclusion that it is worth every penny in results.