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Do you think there should be best-before dates on compost?


Using old compost won’t do your garden any favours, but sadly, we’ve found a lot of it for sale on shop shelves. It’s time to introduce best-before dates on compost – and now B&Q’s investigating the idea…

We’re very pleased to report that Britain’s biggest retailer of compost, B&Q, is extremely interested in putting best-before dates on compost packaging and help prevent out-of-date stock from hitting the shelves.

We met with B&Q recently and were told that the company is going to be conducting its own independent tests to research the issue. Tim Clapp, horticulture and garden care lead buyer at B&Q, told us:

‘We’re investigating the shelf life of compost to ensure customers get the best possible experience from any bag they buy [from us]. We’ll determine our response when the findings are in.’

The importance of compost lifespan

B&Q wants to run the testing to understand the lifespan of its compost, as it varies between different formulations. The time it takes to release the fertiliser that composts contain depends on a number of factors, such as temperature and the conditions that it’s stored in, and this accounts for how quickly it deteriorates.

B&Q is planning to explore the impact of these different factors by running independent tests over a 12-month period at the East Malling Research Centre. The retailer’s currently working on a brief for this trial and aims to kick-start it this month. It will cover the full range of composts it sells, from multipurpose to ericaceous, seeds and cuttings to containers.

How old is your compost?

As B&Q sold more than 10 million bags of compost last year and there are currently two B&Q products that are Best Buy composts, it would be a fantastic result for gardeners if the company adopts best-before dates.

We found huge amounts of old compost on sale for the third spring running when we were buying the compost for our own trials earlier this year, so it’s still very much a problem for gardeners trying to get decent results.

We’ll keep you up to date with developments from B&Q once it has completed its testing and will continue to call for other manufacturers and retailers to put best-before dates on their compost bags. In the meantime, we’d love to hear whether you’ve bought compost you suspected to be past its best.


Whilst I think it is a good idea for them to be dated ON production think perhaps it would be helpful to mention the alternatives.

This is Norfolk CC
“Home composting allows you to compost kitchen and garden waste at home. It can take between six months and one year to make compost, at which point it can be put directly on your flower beds or lawn or used in plant pots.

Why not invest in a compost bin? Please visit http://www.getcomposting.com for special offer bins.

You can volunteer to spread the message about composting as part of the Master Composter Scheme in Norfolk. Two-day training courses are held on a regular basis. As a volunteer, you can help your friends and members of your family and your local community to get composting at home.

Community composting schemes are schemes where communities volunteer to collect garden waste from local households, and then manage the material to make compost that can be used by local residents.
Buying Compost

You can buy compost from all of our 20 Main Recycling Centres.

Each 40 litre bag costs £3.50. If you would like a large quantity (e.g. in excess of 20 bags), please call us in advance on 0344 800 80 20 and we can check if the recycling centre has enough in stock. Alternatively, there are a number of composting facilities in Norfolk where residents may be able to buy compost from directly.”

The community composting projects attract over £50 per tonne which seems a splendid concept.

I make compost at home from mowings and prunings. It has little nutrition but makes a good soil improver on our heavy clay soil. Other stuff goes in a garden waste bin that the council collect and process; unfortunately they do not sell back to the public, only to farmers. I’m not sure whether I would want it though as all sorts of waste seems to go into it, including my nasty seeding and perennial weeds (like convolvulus) and food.
The idea of community compost heaps attracts me. Particularly if the local stables were involved. It would make another good source of soil improver – a lot only goes a little way.
The compost referred to here though is what I would use to raise seeds, in patio containers and grow on greenhouse plants. I buy as I need it but occasionally have a bag or two left from the end of last season. I haven’t seen any deterioration in results. I’ll be interested to see what this investigation uncovers.

Apropos compost and use by dates I found interesting and will follow the outcomes with interest and hopefully sound advice. But regarding sound advice and compost I feel I was short changed this time round on good advice by Which . As usual I consult Which advice on their best buy composts which are usually on line in early spring in previous consultations I have found such advice spot on. Not this year? I like hanging baskets I also love the lush display of flowers and trailing plants. This year Which recommended Fertile Fibre it came out top of the survey by a considerable margin. It is apparently peat free and Organic? It was also by a considerable margin the most expensive. The on line review made a point of the fact it was for container planting and hanging baskets apart from the description of the growth rate of I believe potatoes and a certain type of popular flower ( I forget which) that was the on line information. Anyway based on reliable past Which information I purchased a bag the the gentleman who I spoke to at Fertile Fibre was amicable and suggested the multi- purpose product. So fine I purchased a bag it arrived following day postage free-excellent. Problem was It was useless for hanging basket growth very little was happening. I particularly like Black eyed Susan flowers. In previous years using peat based compost they have been lush and profuse attracting lots of admiring comments. Not this year. Anyway I contacted Fertile Fibre I was told that peat free compost was like driving a super car as opposed to the usual everyday saloon etc. He gave further advice but also said I would have obtained better results with their Container Compost-after selling me General Purpose. When I contacted Which they told me that they had explained the way one should use a peat free fibre compost. Not on the website their was no mention of this. It was apparently explained in the Gardening Magazine. I do not get the magazine. So for me it turned out to be a very expensive operation in fact loosing patience I purchased planted baskets. First time I have done this. But the plot thickens (pardon the pun) Checking the Which web site I found they had published the full results of the various compost tests and the vaunted Fertile Fibre was way down the list scoring list just 42% as opposed to 88% in their recommended list? Anyway will be much more careful in looking at these recommendations in the future. I agree peat free is the way to go IF it delivers. But thank you Which for all the sound advice it gives and will hopefully continue to give. My apologies for going off the original thesis about compost but hopefully this will alert readers to the difference using PEAT FREE.

I am interested in what is happening to compost during storage to make it less effective. Are there any scientific studies?

Has Which? asked the RHS or the John Innes Centre for example for research they may have done on the life of compost, its constituents and the consequences of deterioration?

I’m reminded of the old lady who bought a grow bag. She watered it every day, but nothing grew. I have always pulled one from the pile, carted it home and used it to “improve” the flower bed soil. They do break up the soil and give it a nice colour, though it is sometimes surprising what one sometimes finds lurking in the compost. I supplement this with a couple of proprietry feeding products. The latest one has produced dramatic results on everything it touches. I agree that there should be some indication of the sell by date if it is proven that these bags lose their efficacy over time.

I like the sound of efficacious compost. Better for the Which? Hazel I suppose.

We have often bought multi-purpose compost ten bags at a time and had full and part-used bags left over for many months. We have not noticed any particular loss of quality but that is probably because we have really only used it in a general way as a general soil improver rather than a propogating medium, conditioner or nutrifier.

Very good, John. Now how about an economical efficacious ericaceous compost?

Joe McWilliams says:
15 September 2015

Being peat free is the most important step you can make. Peat releases a lot if CO2 when it is dug up. We only started using it in the second half of the 20th century and managed fine before then. Out of date compost that has slow release fertiliser in will not be as good, but will not harm. Switch to coir, wood fibres, and soil conditioner from your local recycling centre.

I think the issue is less about the efficacy of old compost but the health effects. Some old compost I’ve bought has been covered in a white mould and has given off clouds of spores when disturbed. I believe a man died once from inhaling fungal spores from old compost.

Go to this weblink and see why B&Q are investigating , they’ve been selling unusable product and gardeners have suffered!


Regrettably in an effort to abolish peat many composts do contain a lot of rubbish as a means of holding the added nutrients. I still buy peat-based composts as they are the only ones I’ve found so far that give a reasonable performance. I’m sure the “greens” will wish me burned at the stake for admitting to this. However it does end up improving the good things to eat that I grow that do not have to be shipped from all points of the globe – there is a quid pro quo.

20 July 2020

I have bought compost which had totally dried out – like dust. On the reverse was the date 2017 and it is now mid-summer 2020! Does the date refer to date of production and do you think I have a claim in returning it?

Helen – Sometimes garden products like composts, fertilisers, growth promoters and other mulches or soil improvers are offered at reduced prices if they are an earlier year’s production. I assume you paid the current full price and that it was not marketed as a stock-clearance promotion or with any indication that it was three years old. I would expect the date shown is the year when it was bagged; the contents could be even older.

It is not necessarily bad compost and might perform as well as more recent production in terms of nutrients once it is integrated with your garden soil. I think the problem will be – depending on its composition – that there will have been further decomposition of fibrous material, some dissipation of the nutrients due to evaporation, and a decrease in moisture retention and weed suppression. You might need to use more than you otherwise would in order to compensate for the lack of ‘substance’ or ‘structure’ in the product. A handful of good compost will hold firm but if yours has crumbled to dust it will presumably just fall off your hand.

I think you should submit a claim to the retailer for replacement or a full refund on the grounds that the product is not fit for purpose and not as described.

It would be useful to know what make of compost you bought and where you bought it [i.e. on-line, garden centre, supermarket, independent shop], and the volume per bag and the price paid.

Many gardeners keep unused compost from one season to the next but that is their choice. It should at least be sold when fresh or if not then marked as older stock with a commensurate price reduction.

5 years ago, apparently, B&Q told Which? they were going to launch an investigation into the shelf life of their composts. Perhaps they have some results that Which? could report on. @gmartin, George, is there any news from B&Q?

I’ve done some digging and it looks like B&Q told us they comissioned research but never shared the results with us.

Adele says that the wider industry continues to be against putting sell-by dates on compost as it would mean retailers would be forced to reduce the selling cost on compost at the end of the gardening year. As compost is already a loss-leader, further discounting would mean more financial loss.

The Gardening team carried out testing on old compost and published the results in the Jan/Feb 20 issue.

The results were, as you might expect, use fresh compost.

The Which? advice remains as before – don’t buy faded or ripped bags, avoid heavy bags as they have almost undoubtedly been soaked by repeated rain showers which degrades the compost and, where possible, buy from garden centres that store their compost under cover.

Thanks, George. It was good of you to do some digging . . .

I carried some compost over from last year and I am glad I did because it was nigh on impossible to buy compost earlier this year because garden centres and other outlets were closed and in other stores the products were only available in small bags at high prices. Buying on line is relatively expensive and I have in the past experienced delivery problems because of its bulk and weight.

When I think back to my younger days, hardly any commercial compost was used. People either had a compost heap which took forever to produce a quantity of useable material or they just managed without or used manure if they could get any conveniently. There were very few of the modern plant foods, treatments and pesticides that nowadays fill the shelves of the hardware stores, garden centres and even the supermarkets in the season [and if compost is a loss leader then these products surely are big profit makers, so if people go in to buy some compost and they also come out with a basket full of speciality additives then the garden centres have nothing to complain about].

I’m not sure that the horticultural results in my parents gardens were any worse without these preparations than today’s gardens.

The compost Helen bought was dated 2017. For that to still be on sale in 2020 [possibly four seasons after it was made] to me shows a lack of proper stock control. It was probably left at the bottom of a stack and new product was stored on top of it. The old stock has just emerged and has been sold without checking the date.

Garden centres are not especially good at showing unit prices and compost comes in odd volumes with different manufacturers using different amounts per bag. It also varies between types of compost because the densities differ. Bags need to weigh no more than 25 kg for safe manual handling so weight might be a better measure than volume. All this means that it is not easy to compare prices and there are also the various offers that further complicates it – 3-for-2, and 4-for-3, or three for £19, etc, and sometimes with another product thrown in as a bonus. If you want it delivered that adds anther dimension: free delivery usually means a higher price per bag.