/ Food & Drink

Twisted tomatoes – is weedkiller in compost to blame?

Veg grown in compost bag

Have you had problems with plants grown in bought compost this year? We’ve heard stories that some tomatoes have shown twisted, distorted growth and had to abandon a trial of potatoes grown during our trials.

Recent media reports have suggested that clopyralid, a lawn weedkiller, may be present in composts. It’s thought that it may have got into mixture via council green waste, an ingredient in many bagged composts. Clopyralid contamination has already been a problem in the United States and New Zealand, so could the same thing be happening here?

The Sun’s Peter Seabrook has levelled criticisms at peat-free composts in particular as some contain green waste. But green waste is likely to be an ingredient in many composts, both peat-based and peat-free.

Herbicides affect garden growth

Now it wouldn’t be the first time that herbicides have affected gardeners – aminopyralid, a herbicide used on pasture, recently found its way into manure and then onto people’s veg plots, killing sensitive crops.

The Waste & Resources Action Programme (WRAP) is looking into the suggestion that clopyralid has got into composts, but points out that plant problems can be caused by a number of other factors, including viruses and over watering. It also points out that a compulsory test for herbicide contamination is carried out during the compost manufacturing process.

Digging the dirt

I wonder if gardeners know whether it’s safe to put grass clippings containing clopyralid on the compost heap or the council green waste. Labels on lawn weedkillers containing clopyralid (such as Evergreen Lawn Weedkiller, Verdone Extra and Vitax LawnClear2) are ambiguous, but in essence, any grass clippings that have come into contact with clopyralid should be put in the waste bin rather than used on the heap or put in the green waste bin.

I’m worried that manufacturers don’t spell this out for gardeners. Also, many people pay companies to care for their lawn, often using chemicals, and may have no idea that their grass clippings should not be put on the compost heap.

We’re keeping an eye on the situation and will let you know if we learn anything more. The compost that affected our trial is being analysed, and we’re also awaiting the results of our latest compost trials due to be released early next year.

In the meantime, if you’ve had problems with compost this year, we’d love to hear your experiences to help inform our findings.


I had a problem with Westland this year. With a very large variety of my veg and flower sowing, probably 80/90 % of seedlings suffered and stayed tiny and distorted once they had appeared. Even nasturtiums struggled. I eventually repotted everything into a different compost and everything apart from beans came on leaps and bounds within days. The beans have grown but look very poor.

I’ve suffered from using Bord na Mona compost this year. Tomatoes all stunted. If its weedkiller how do I find out if the tomatoes are safe to eat? Heartbreaking :-((

I purchased a quantity of Bord na Móna Growise Vegetable Peat Free Compost for my allotment and polytunnel.

I suffered poor germination, stunted growth and bizarre shaped leaves and fruit.

I believe this product is contaminated with clopyralid, aminopyralid or similar

I have done a bio-assay test and this clearly shows the product is faulty

I have contacted my local supplier who offered me more compost! I have written to the company and await a response.

This is surely an issue for Which? to pursue?