The watercress industry has been enjoying a renaissance as the "superfood" qualities of the semi-aquatic crop have become more widely known - especially its potential to help fight cancer.
During the past decade, retail sales of the product have soared from £30m to £60m. But the boom has led to new producers trying to exploit the market by cutting set-up costs and growing the salad leaf in polytunnels on land - but still marketing it as watercress.
The NFU Watercress Growers' Association, which has seven members and which has been going for some 75 years, fears this will damage the industry and has applied to the EU for Traditional Speciality Guaranteed protected status of its growing methods.
Association member Dr Steve Rothwell said: "We are all very angry about this as we have spent a lot of time and money on promoting the health benefits of watercress, which is why the industry is now reaping the rewards.
"Another benefit is that water-grown watercress can be cultivated all year round in the UK, without artificial light or heat, unlike land-grown cress.
"There are tremendous infrastructure costs in growing watercress and obviously the location is also critical so we can harness only the purest flowing water available, from which watercress derives its bounty of nutrients.
"These new producers are just trying to cut corners and pass off an inferior product as real watercress. There are just a handful of these growers at the moment but if they continue to get away with it then more are sure to follow, which will put the whole tradition of growing watercress under threat."
Chairman of the association and head of The Watercress Company Charles Barter added: "It's very difficult to point fingers at who is doing this as there's no auditing system in place. But we know that much of it is coming into this country from other parts of Europe, in particular Spain."
Only traditional products can apply for Traditional Speciality Guaranteed status, which is currently enjoyed by products such as Parmesan cheese.
To qualify, a crop or food has to have been produced in the traditional manner for at least 50 years, and the majority of applying member-state producers must conform.
The association stands a good chance of approval as it has more than 200 years of continual cultivation history.
It applied for the status a year ago and in the past few weeks has had its application accepted by Defra. ADAS and Defra must now consult with industry bodies, allowing three months for objections.
The application then goes to the EU, which can take another 18 months.
BENEFITS AND RESEARCH
Watercress contains more than 15 essential vitamins and minerals and, gram-for-gram, contains more vitamin C than oranges, more iron than spinach and more calcium than milk.
Research by the University of Ulster, Coleraine, published in February 2007, found that watercress increases the ability of cells to resist DNA damage caused by free radicals, and that a daily diet of watercress reduces levels of DNA damage found in blood cells. DNA damage is considered to be an important trigger in the early stages of cancer.
A study funded by the Watercress Alliance - made up of Vitacress Salads, Bakkavor and The Watercress Company - is being carried out with the University of Southampton. It aims to identify the plant's ability to suppress breast cancer cell development through a clinical trial with breast cancer survivors. Results are due in February/March 2010.