It began as little more than a spat between a group of nimbys and a fruit grower in a beautiful corner of the countryside immortalised by Wordsworth. But a dispute snaking its way through the judicial system has been transformed into a battle for the British strawberry.

The epic confrontation – over the humble polytunnel – is pitching conservationists against farmers, nature against agriculture, man against the seasons, in a classic stand-off that could come straight from a script of The Archers.

The gauntlet was thrown down by a Herefordshire conservation group that challenged a decision by the local council to grant planning permission for polytunnels covering 54 hectares in the picturesque Wye Valley. The Wye Valley Action Association (WVAA) claims the structures, adjacent to an area of outstanding natural beauty, are an eyesore, responsible for "landscape blight".

It appealed against the decision in the high court, where a judge found the council had made an "error of law" by failing to ensure an environmental impact assessment (EIA) had been carried out at the site in compliance with a European Union directive.

Giving the background to his decision, the judge, Ian Dove, even quoted Wordsworth, whose walks around Tintern Abbey on the banks of the Wye, prompted him to write: "How oft, in spirit, have I turned to thee, O sylvan Wye!" Dove noted the case hinged on issues that concerned Wordsworth – "the natural landscape and those who tend it". He ruled the polytunnel site should be subject to an EIA because it was close to a conservation area and a site of special scientific interest overlooked by a historical monument, Goodrich castle.

The ruling raised eyebrows because it recognised the impact of the development on the surrounding countryside, not just on the farmland where the polytunnels were erected.

The National Farmers Union, which claims 90% of strawberries grown in Britain are produced under the temporary structures, fears the decision will have wider implications if allowed to stand and will support a legal challenge in the Court of Appeal in November.

Much is at stake, not least the length of the farming year. The British strawberry industry is worth almost £400m a year and now stretches from early spring to late autumn.

"Polytunnels have been largely responsible for the success of the berry industry over the last couple of decades," said Phil Hudson, the union's chief horticultural adviser. "They have extended the fruit-growing season from 12 weeks a year to six months, reducing the need for imports. Without them we would be exporting jobs outside the UK. They are going to become even more important as the UK seeks to ensure its food security."

In 2008 a landmark planning inquiry heard evidence from a farmer who claimed that during the wet summer of 2007 he would have lost 50% of his crops without polytunnels. This would have had an impact on the catering at some of the UK's most prestigious sporting and cultural events. About 60,000lbs of strawberries are eaten during the Wimbledon tennis tournament alone.

The outcome of the appeal could have implications for fruit growers across Britain who use "Spanish" polytunnels – walk-in tunnels made of polythene sheets tied to arches – that are subject to planning permission from local authorities. The structures are found in the fruit-growing counties of Gloucestershire, Somerset, Kent and Worcestershire, but are a common sight across the UK.

Conservation groups claim their use is more than simply an eyesore. They say the structures deter tourists from visiting the countryside, affect water tables and increase traffic. Polytunnel farms also rely heavily on migrant workers for fruit-picking, leading to the creation of unsightly temporary caravan parks.

But their success means they are now used in other areas of fruit production. A submission to a parliamentary committee from one conservation association claimed: "Polytunnel operations are quasi-industrial processes now diversifying from strawberry growing to other high-value crops such as asparagus, raspberries and even dwarf cherries."

Paul Stookes, the solicitor acting for the WVAA, said it was important the law recognised that polytunnels must be subjected to environmental assessments so that all in the surrounding community could comment on their construction.

"There are real tensions in food production," he said. "We should be producing food locally, but you have to question whether we should be producing summer fruits in February."