A batch of courgette seeds sold by a major supplier has been recalled after producing crops which made people ill.
Mr Fothergill's seed company, based in Newmarket in Suffolk, issued a warning against eating the bitter fruits.
It said some seeds produced courgettes with "abnormally high levels" of a naturally occurring chemical which caused nausea and diarrhoea.
Four families in Castle Acre, Norfolk, reported feeling unwell after eating the produce they had grown.
Jim Moriarty said his wife was "not well at all with cramps, diarrhoea and vomiting" after eating the courgettes.
"You cannot tell from the look of the seed that it is a problem. I think they need to go back to the original source and prevent this from happening again," he said.
The firm has advised customers to throw away plants if the courgettes taste bitter and not to eat them.
On its website Mr Fothergill's said it had traced the seeds to seeds a grower "with the most meticulous growing and husbandry routines".
"The incidence of this problem is extremely rare, but not unknown," it added.
It said the bitterness "could be due to unusually high levels of cucurbitacins, a naturally occurring compound that is present in all courgettes, cucumbers and squash".
Mr Moriarty, who began growing vegetables as a result of the coronavirus lockdown, said he was also advised by Mr Fothergill's to "lick a courgette first" before cooking or eating them and not to consume them if they were bitter.
He said he had not been put off growing courgettes in future.