It may be a matter of bitter disappointment to many Yorkshire folk, but Edmund of Langley, the founder of the House of York, was born in Hertfordshire. Yet they could excuse his origins because he bequeathed something special to the county that was synonymous with the dynasty he founded – its white rose.

More than 700 years after the Plantagenet's death, his floral emblem has become the subject of a struggle as lawyers representing two neighbouring Yorkshire brewers – one large, one small – square up in the High Court to argue their claims over the right to use the symbol in what has been dubbed the civil war of the rose.

The tiny Cropton microbrewery, founded by two brothers, Phil and Paul Lee, in the cellar of their pub near Pickering in Ryedale in 1984 (but now operating out of a farm building) has incurred the wrath of the county's oldest beer maker, Samuel Smith's, which is based down the A64 at Tadcaster.

Smith's is known for the low cost of the ales sold from its 300 pubs and the independent family brewers, founded in 1758, still use traditional production techniques – including a pack of working dray horses.

But Smith's took exception to its rival's decision to use the white-rose symbol as part of the packaging for Yorkshire Warrior Ale. Proceeds from sales of the beer go towards helping wounded soldiers from the county regiment. The trademark dispute, after brewing for years, is being laid out this week before Mr Justice Arnold with both sides claiming damages. Clive Auton, Smith's former export manager, told the court that Smith's started using the rose symbol four decades ago after consulting with advertisers.

Cropton's lawyer, Mark Engelman, argued that the white rose is a symbol of the county and the Yorkshire Regiment and has been used in many ways by other companies and organisations, including Leeds United Football Club.

Denise McFarland, Sam Smith's lawyer, rejected the claim and said the Warrior label was "confusingly similar" to the Smith's logo.

She said Smith's was not trying to win a monopoly over the use of the emblem, since there would be no objections to its use in unrelated circumstances. "If a rose device is used on a wedding dress shop in Pickering or a taxi service in Devon, that is not something of which we would have any complaint," she said.