Saturday, 1 June 2019

That weedkiller problem again!

One of the most annoying problems I have to cope with in my garden is the repeated occurence of weedkiller contamination in commercial compost. I use a lot of compost and can never produce enough home-made stuff to keep me supplied, so I have to buy it. I have tried many different brands, and I have encountered problems with many of them, particularly in relation to the generally poor quality of this sort of product (lack of nutrients, poor moisture-retention, presence of plastic, metal, wood etc), but the worst issue is that of the weedkiller.

Tomato plant exhibiting symptoms of weedkiller damage - photo from 2014

The sort of weedkillers that I'm referring to are mainly clopyralids used in domestic lawn-care products and aminopyralids used in agriculture to destroy broadleaved weeds in pastureland. These substances are incredibly powerful and very persistent. Unfortunately they often find their way into compost. One of the routes the clopyralids take is via lawn clippings deposited in Green Waste Recycling schemes - even though the manufacturers of the weedkillers advise against disposing of lawn clippings in this way. The aminopyralids are most likely introduced to gardens through the application of contaminated farmyard manure.

When you buy a bag of compost there is no way that you can tell whether it is contaminated (short of laboratory testing, I mean). It's just "a lottery" as they say. If you buy two bags of the same compost you may find that one is contaminated and the other isn't. If you are really thorough you can carry out a Bean Test on the compost, that's to say sow some Broad Beans in it and see what happens when they germinate. Broad Beans are amongst the most susceptible to damage from these types of weedkiller and will quickly display the symptoms if the compost is contaminated. By "quickly" I mean a few days after germination, so the whole process will likely take 3 - 4 weeks or more. But who has the patience (and time) to do this with EVERY bag of compost they buy? And why should they have to anyway? I feel very strongly that it should be incumbent upon the manufacturer to test their product before sale in order to ensure that it is fit for purpose - i.e. not containing chemicals that will harm plants!

This year I have again been hit with the problem. Unfortunately, by the time you realise there is a problem, the damage has already been done. Some plants take quite a while to show the symptoms (e.g. tomatoes), but others respond more quickly. I think I have probably got off fairly lightly this year (famous last words...) because the damage I have seen on my plants appears not to be too severe. The beans are definitely affected. These are Runner Beans. Notice the distorted, wrinkly leaves.

These are Broad Bean leaves - curled, pale and pitted:

These potato leaves show the characteristic "spooning" effect that seems peculiar to them. The leaves curl up at the edges and have deep depressions in the centres.

Some of my chillis look like this, with wrinkled foliage:

Others have thin, spindly leaves, in this context often described as "fern-like".

This effect also frequently occurs on tomatoes. So far this year my tomatoes are not showing symptoms of contamination, but I expect it is only a matter of time before they do, because some of their growing-medium is comprised of the suspect compost. I also know that tomatoes are typically slow to exhibit the symptoms.

The trouble is that for me it is hard to be 100% sure which compost is the culprit, simply because I typically grow most of my plants in a mixture of different stuff. For example, the tomatoes are in a mix of garden soil, homemade compost, commercial multi-purpose compost and material from dedicated tomato Growbags. This year almost all of my little plants were raised initially in Levington's John Innes No.1 compost (specifically formulated for seed-sowing) and then potted-on into Westland Jack's Magic multi-purpose compost (MPC). When the plants got bigger they were potted-on again into their final homes. At this stage the chillis and tomatoes were put into big pots containing more of the MPC, along with some of the Levington's Tomato Growbag material, with its added nutrients. Circumstantial evidence points towards the culprit being the Jack's Magic. Regrettably I now realise that this compost was also implicated in the disastrous contamination I experienced in 2014. I should have known better than to risk using any of that company's products again!

Although I am annoyed and disappointed by this new contamination episode, I know that the damage to my plants may not be catastrophic, and many of them will probably "grow through it". However, I fully expect some of them to succumb and all of them to produce lower yields than normal, possibly with some distorted / malformed fruit. Still, I feel this whole subject to be little known and under-reported, so I shall continue to do what I can to give it a higher profile.

You can find out more about this issue HERE, but be aware that this site is provided by Dow AgroSciences UK, who are one of the producers of the weedkiller, so they have a vested interest in downplaying the problem!

If you feel the need to report a case of damage caused by weedkiller-contaminated farmyard manure, you can do so by contacting the Health and Safety Executive (HSE) via this link:-

Reporting problems with contaminated farmyard manure.  Be aware that the HSE will probably pass you on or refer you to Dow AgroSciences anyway.

Reporting of damage to plants caused by clopyralid-contamination in commercially produced garden compost seems to be a grey area and I'm not qualified to give any advice about who to report it to! The authorities seem to be only interested in harm caused to people, pets or "the environment". In the first instance I suppose you have to take up the issue with the producers of the compost you believe to be contaminated. However, if my experience is anything to go by, they will do their damnedest to reject any responsibility whatsover, and will insist that you produce loads of evidence that you probably won't be able to provide. Good luck!


  1. I am using Wicks compost with good results so far, I never buy Verve from B&Q, or any with peat in.

  2. I had half thought that this problem was over once the neonicitinoid spray was banned in the UK (at least temporarily) but then again chemistry isn't my strong suit and those long names just make my eyes roll back into my head. As you point out we all have to become experts if we are to challenge the manufacturer.

  3. Charles Dowding has been on this recently, his latest blog post mentions it.

    I'm guessing it's a double whammy of it getting sprayed more often, and various kinds of this type of waste now being used in composts, to replace the peat.

    1. I think Charles' blogpost was inspired by a discussion he and I had on Twitter a couple of days ago! This problem is a lot more widespread than you might think.

  4. What do you do with your old compost Mark? I'm afraid we do used peat based products. I read an article that said contrary to the hype, garden compost is a mere drop in the ocean as far as peat bog destruction. The burning of peat bogs and using peat as a fuel cause the majority of the damage and stopping using peat compost will have little effect. If manufacturers produce a viable safe alternative, it would be different.

    In a bag of compost you could have some parts contaminated and other sections not.

    We are into the 11th year of this problem and it is still prevalent. When we were affected we carried out a media campaign on TV, radio, newspapers, letters to MPs, government ministers and MEPs that resulted in discussions in Parliament but still many people were unaware We tried to get garden centres to put up posters which unsurprisingly they didn't. We contacted Trading Standards and the HSE but unfortunately there are few controls where gardening products are concerned. We had many phone calls, emails and visits from a representative of the manufacturer which resulted in a temporary withdrawal of the chemical. It was reintroduced after some changes to the labeling. Some garden experts didn't understand how it worked advising people to flush it out of compost. I'm not sure what else we could have done but as I say here we are over a decade later. We gardeners are not important enough it would seem.

    1. Sue, if I can positively identify contamination in compost I take it to the tip (the task was a big one in 2014!) Otherwise I reuse it - which I know is a danger, but I can't afford to buy loads and loads of compost every year, and of course there is no guarantee that new stuff would be any better! I'm afraid this problem is only going to go away when people stop making this type of weedkiller. I see some signs of hope in the recent court judgements against Monsanto and Co. They will only stop manufacturing these chemicals if it becomes unprofitable. I wish we could get Monty Don or someone similarly high-profile to take up the issue. BTW, I think you are right about the peat too - domestic gardeners are only a very small part of that particular issue.

    2. I did try to get a celebrity gardener involved back when we had the problem. The nearest I got was an appearance on Gardeners’ World. I also managed a slot on our local Politics Show . I think the problem doesn’t touch them as many make tonnes of their own compost. There is also lots of people giving out poor advice as they just don’t understand how this stuff is different. I’m guessing that you know enough not to compost affected plants.

  5. I have had similar with my chilli plants. I think you can get wool based compost so might be worth a try though may be a bit more expensive.

    1. Yes, I'm aware of the brand called Dalefoot. It's made mostly of sheep's wool and bracken. The trouble is, it's about four times the price of ordinary multi-purpose compost!


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