Aminopyralid contamination of home gardens and allotments is back. Every day I am hearing of new cases of carefully nurtured crops maimed and wiped out by this dreadful chemical. I’m not an alarmist sort of person but this is totally avoidable and – what makes it even worse – this is not the first time that aminopyralid has been responsible for widespread contamination of our plots.

What is this chemical, how is it spreading and what can we do?
It is really sad. Small scale growers, home gardeners and allotmenteers all doing what they feel is the right thing, growing as naturally as they can and using local resources to make their compost or buying from trusted garden companies, are unknowingly introducing this hormone mimicking herbicide to their plots. Just the tiniest trace can contaminate, harming and killing peas, beans, tomatoes, potatoes, lettuce, spinach, Jerusalem artichokes and peppers, plus many kinds of flowers too.

Sorry to write a gloomy post – I don’t have it myself, these photos are all from other gardens, but I think it is such an important issue.

Considering the number of people affected, more every day, the government and Dow are being rather quiet on the subject. So, many of us home growers, bloggers, social media users and You Tubers are coming together to do what we can to spread awareness of the problem and let fellow gardeners know what they can do to help.

Many don’t realise that they have it, blaming aphids, disease, weather or just bad luck.

Manufactured by Dow Chemicals, aminopyralid and clopyralid (a similar herbicide) are widely used by farmers to kill broadleaved weeds in grass and rape straw. As well as broad leaf weeds it kills poppies.

The agrochemical branch of Dow is also known as Corteva. Bizarrely they run something called The Environmental Respect Awards – astonishing “green was” from a company that manufactures and promotes these dreadful herbicides that are harming the gardens and allotments of regular folk. (The winners are not exactly what one would consider “environmental”).

Worryingly, it is also found in domestic herbicides for home use available in garden centres. This herbicide does not break down in the composting process and contamination is being reported in council composting systems.

Aminopyralid was approved for use in the UK in 2005, and I first heard about the terrible problems it can cause, destroying gardens and allotments, over a decade ago when news of distorted tomatoes, beans and potatoes spread from allotments to the RHS and into the media.  Use was suspended in 2008 when new rules were brought in, designed in theory to prevent the herbicide from entering domestic composting systems. The chemical passes through animals feeding on grass or hay and goes into their manure. It also remains in grass and hay that is composted.

The problem did not go away. In 2011 George Monbiot’s article explained some of the dreadful consequences of this herbicide and called for a suspension of sales. But that didn’t happen. It has continued to be a problem each year since then for some gardeners, usually brought in via horse manure, and we for the past decade we have been advising that people using horse manure check for aminopyralid (see bean test below) before using. However this year the cases of contamination have increased significantly.

In April Charles noticed that the broad beans on a small area of his garden were looking unhealthy: pale, weak and much smaller than neighbouring beans sown at the same time. Closer observation revealed the tell-tale deformed growing shoots: aminopyralid contamination.

The difference between this patch and their neighbours? The compost – here Charles had spread some homemade compost that had contained a small amount of manure and hay from the neighbours’ horses. He has been using their waste manure and bedding for seven years. Aminopyralid is so strong that even small amounts can contaminate.

The beans have now been replaced with sweetcorn, a relative of grass and therefore unaffected by the herbicide, to see what happens.

Here you can see the patch with the healthier beans growing alongside: healthy towards the front and rear of the photo.

Charles made a video explaining what happened here and what he has done subsequently, and also in this blog post.

And then almost daily we have been hearing of new cases, directly and via social media: a well respected gardener has had significant damage to her flower crops from contaminated compost, a visit to a newly established veg garden on a large estate showed distorted beans and peas, and comments in our no dig Facebook group as people anxiously put up photos of suffering veggies.

Other bloggers are writing about their experiences including Sustainable Skerries in Ireland who have experienced a terrible contamination.

Aminopyralid is turning up in some (not all!) horse manure, cow manure, chicken manure, small animal poo/bedding, green waste compost, straw, hay and grass (used to feed/bed animals and also on their own as mulches or compost ingredients) and in some branded composts from stores, so it is a potential problem for everyone even veganic  growers (until recently it seemed to be just a risk for people using manures).

Some people who have bought contaminated bagged and branded potting compost from shops and online retailers have been having the most awful experiences, even being threatened with legal action for complaining that the compost has caused problems (legal advice was taken and the brand can not sue). The same brand is mentioned in this RHS site from 2008. Others are being met with a wall of silence from the companies.

It is unlikely that the companies themselves knew that they were putting contaminated composts into their products – indeed it would be bizarre of them to do so. There is supposed to be a traceability, the treated grass (manure, etc) is not supposed to be entering the composting system, but it is and increasingly becoming more so. They probably had no idea that there was a risk.

+++ Worth pointing out that so far most store bought composts seem to be fine! Don’t panic. Charles lists some of the brands which are being named here +++

Is it safe to eat plants grown in contaminated compost, or milk or meat from animals eating the grass and hay? Dow suggests “yes” as the trace will be small, but my opinion is that we really don’t know and back in 2008 (see the links in this blog post) Dow was advising people not to eat plants from contaminated soil. This would not be the first time that a large chemical company has assured us of the safety of their herbicide only for scientists to prove otherwise.

Has it been tested and declared safe for the food chain? I can’t find any evidence that it has.

The contaminated compost starts to break down in contact with soil bacteria, which is some good news for no dig gardeners as we certainly have plenty of healthy soil life (seems a bit unfair on soil bacteria to have to deal with this, though!) We don’t really know how long it takes, a couple of years at least is suggested.

Can you compost contaminated plant matter? We don’t know for sure, but for peace of mind make a separate compost heap and use that on shrubs or trees which won’t be affected by any residue.

So what can we do?

There is a petition to get the chemical banned here. Write to Dow, your MP, the NFU, your newspaper, local press, favourite gardeners, the compost companies, ecological bodies and anyone else you can think of who can highlight the issue.

Check all composts before spreading and make as much as you can at home if possible. If you don’t have much now use alternatives such as comfrey and nettle feeds.

How to test for aminopyralid

Fill pots with composted manure (or whatever compost you are testing).  Have a couple of extra pots with “safe” compost in as a comparison. Sow beans and wait 2-3 weeks. If the compost is contaminated then you will see the distorted growing shoots develop.

Iain Tollhurst recommends using clover as it will show even the tiniest traces of aminopyralid (one part per billion) but we are not sure which would be faster to show the contamination.

Written by Stephanie Hafferty

Organic no dig kitchen gardener, plant based cook, award winning author and writer. Loves growing, food, making potions, crafts.


    1. I don’t have them I’m afraid and working all day today at BBC Gardeners World Live (2 no dig talks 🙂 ) but if I find out will post it here.

      Very good idea about a sample letter!

  1. Thank you so much for this information. I have now written to our local MP, asking for her to bring the matter up. It affected my crops this year, It’s horrific, very upsetting, and so frustrating that there is no one to turn to.

    1. It is frustrating that there is so much confusion about who to approach. I am so sorry to hear about your crops 🙁

    1. Thank you, I had a great day at GW Live. Looking forward to hearing some talks myself tomorrow 🙂

      Yes, it isn’t a good situation but I am optimistic that it will be sorted out.

  2. We have just spent hundreds of pounds on our new allotment and filled the beds with over 30 bags of “country organic natural stable manure” also mulched our much loved roses with it.
    Everything apart from the brassicas we have lost and are devastated. I sent pictures To Charles and he has confirmed it is Aminopyralid damage. We have 4 beds full of cabbages, kale, PSB and Brussels sprouts which have grown fine as it doesn’t “affect” brassica growth but now we don’t know if they are safe to eat? Would you eat them?
    Charles now has our evidence to add to the dossier, I have contacted the garden centre where we bought the stuff and I will be contacting Dow and my local MP.

    1. I saw the photos yes, so sorry for you. At the same time as reading this I have heard of another plot similarly contaminated with this very brand.

      I shouldn’t think anyone knows for sure whether it is safe to eat brassicas grown in the contaminated soil, the information out there is contradictory. One might imagine that it isn’t any worse than eating lunch in a regular restaurant where vegetables which are not organic are served, but I really don’t know. This chemical harms plants with the tiniest trace, so the actual contamination is likely to be quite small.

      Charles is growing sweetcorn in the bed where he had the contamination and he’ll eat those.

  3. Thank you so much Steph for the talk at gardeners world your last comment about the weed killer was a light bulb moment for me as I had the problem in 6 bags of wyevale compost I put in deep boxes in my greenhouse. In fIfty years of growing ve g Organically I had never seen anything like it . I have written to wyevale but they just don,t want to know I have asked them to test . I am the cook at our local lunch club and grow for them to keep the cost down and now will not have. Nearly enough veg for that as well as my own family . When I was growing organically commercially in Lincolnshire In the 1980s i was laughed a t but now the results are being seen so sad. Merle Threadgill

  4. That’s so frustrating 🙁 Do contact Corteva/Dow to report it. I will be updating the Aminopyralid post over the weekend with new information. We had a meeting with their representative this week and information from other gardeners has shown it to be far more widespread in bagged composts than we thought.

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