It is the quintessential English crop, synonymous with the Kent countryside and a key ingredient used to give beer its flavour. But there are fears that traditional British hop farming could die out within a decade, as brewers turn to imports from the Czech Republic, US and even New Zealand to add varied and unusual flavours to their beers.

Kent's ubiquitous oasthouses – many now converted into luxury homes – sprang up in the 19th century to facilitate the drying of climbing hop plants' female flowers. Hops, used as a flavouring and preservative, became a vital ingredient as beer took over from ale as Britain's most popular tipple.

For the past 10 days breweries have been taking part in a new beer festival in the hope of raising the profile of British hops and reinvigorating the industry. More than 20 brewers have dispensed with their usual dried hop recipes at the Kent green hop beer fortnight. They have instead been using only fresh, locally grown "green" hops, which go into the beer less than 12 hours after being picked. Green hops are said to give beer a light and fresh flavour because they retain oils usually lost in the traditional drying process. The beers can only be made once a year, at the end of summer, and brewers say they are unique because it is impossible to make the same beer twice.

Barack Obama uses fresh hops in his own beers, brewed at the White House, the recipes for which were published earlier this month. According to the Campaign for Real Ale there are more than 1,000 breweries in the UK – more than at any time since the second world war. But an increasing number are turning to hops from overseas. Varieties from the US, New Zealand and eastern Europe are favoured by many microbreweries for the stronger flavours they can produce, and hop farmers and merchants fear it could mean the end of the industry in the UK.

Paul Corbett, managing director of hop merchant Charles Faram and Co, said: "Some growers have been idling crops this year because there haven't been enough sales and if they can't sell the hops they pull them out. Our fear is that if demand falls any further then the infrastructure not just for growing, but for picking and processing hops will disappear. If we don't stick up for the UK hop industry now, there will be no industry in a decade's time."

At the industry's peak in 1872, British hop farmers grew around 72,000 acres of the perennial climbing plant, but demand has decreased to the point that last year only 2,500 acres were grown. The only major hop-growing regions now are Hereford and Worcester and Kent. Despite this, the UK is at the forefront of efforts to develop new varieties – including dwarf or hedgerow plants thought to be more sustainable than higher climbing hops – and the revival of old ones. The hedgerow hops cost less to grow, can be picked by machine, are more resistant to disease and require lower chemical inputs.

Eddie Gadd, head brewer of Ramsgate brewery in Kent, said: "Many people don't realise what an incredible range of flavours and aromas brewers can create by using different varieties of British hops in different ways.

"We hope Kent green hop beer fortnight will flag this up to a few more people and in turn raise the issue of what's going on with the UK hop industry and that if we don't use it we'll lose it."

Richard Frost, head brewer at Shepherd Neame, also in Kent, said: "Following the sharp decline of recent decades, we are now at a plateau in terms of acreage. We should be careful not to let the use of foreign hops become a marketing gimmick.

"If British growers can provide what is required in the UK market by developing new varieties, then I can see little reason to import hops. However, I recognise that foreign climates can make a huge difference to the characteristics of certain hops.

"All brewers can do is keep a strong relationship with hop growers and continue to champion great British beer, using British – or in our case Kentish – hops. We are hugely committed to Kentish hops for a variety of reasons. With such an abundance of great hops on our doorstep it doesn't really make sense for us to buy hops from elsewhere."

Gadd added: "We want the fortnight to be a success not just for ourselves but for the UK's hop industry. It would be a national tragedy if this part of our history and heritage was allowed to just disappear."

The good hops guide



According to UK beer sommelier Sophie Atherton, (http://afemaleview.net/) around half of all British wine drinkers can name some of the grapes used to make their preferred tipple, but beer drinkers struggle to name even a single hop. In fact, there are 20 varieties of hops grown commercially in the UK, each of which offer different flavours and aromas to brewers.

The most common varieties in Kent include East Kent Goldings, which has spicy, honey and earthy characteristics; target, which can bring elements of pine, cedar and liquorice; and challenger, with hints of spice, cedar and green tea.

Some of the best beers made with British hops include:

Spitfire (Shepherd Neame): cask 4.2% abv, bottle 4.5%

Broadside (Adnams): cask 4.7%, bottle 6.3%

Canterbury Jack (Shepherd Neame): cask 3.5%, bottle 4%

Gadds' Dogbolter (Ramsgate): cask and bottle 5.6%

London Pride (Fuller's): cask 4.1%, bottle 4.7%

ESB (Fuller's): cask 5.5%, bottle 5.9%

Wainwright (Thwaites): bottle 4.1%.

• This article was amended on 9 October 2012. The original put the number of breweries in the UK at 840. Camra's latest total is 1,009.