Mr Fothergill’s, the Newmarket based seed experts, have recalled stocks of Courgette Zucchini with the batch code I on the packet (located after the printed use by date) as a small number of seeds could produce bitter tasting fruits.

This follows a small number of complaints from customers who have experienced stomach pain and nausea after eating fruits.

All remaining stocks from the warehouse, unpacked seeds and seeds in retail outlets are being recovered and destroyed.

The company believe that the naturally occurring cucurbitacins, which normally exist in very small amounts, have been increased by cross-pollination in the seed production cycle. High temperatures, dryness and other stresses when growing can also cause the increase in cucurbitacins. This causes a bitter flavour and, occasionally, stomach problems once eaten.

Since the flowers are insect pollinated it is possible for a seed received in a seed packet to have been cross pollinated with wild cucurbits, resulting in these high levels of cucurbitacins.

When the cause of the bitterness is bred into the plant like this, the bitterness does not improve with better growing conditions.

The occurrence of this problem is extremely rare, but not unknown, and is untraceable before growing out again for harvest. It is not an issue listed by the Horticultural Trades Association, whose caution labelling guidelines the company voluntarily and rigorously follows. Mr Fothergill’s have traced the problem to one particular lot of seed which comes from a grower with the most meticulous growing and husbandry routines.

It could be that not all plants in a courgette patch could be affected. They can be tasted raw and, if bitter, spit out the sample and discard that plant.

Mr Fothergill’s Tim Jeffries said: “We have reacted promptly to a handful of complaints we have received from our customers to withdraw seed and make efforts to advise customers to avoid any discomfort. The problem is impossible to test for in the seed itself and we have never had a batch of seed like this in our history. We wish to act responsibly and make every effort to advise people.

Anyone who inspects their packets and finds the code letter I printed near the dating information should contact the company through the website mr-fothergills.co.uk and a replacement packet will be sent for future use”