WATER, malted barley and hops. It is the classic recipe for the world’s favourite intoxicant. According to a law declared in 1516 in the German state of Bavaria, a place that likes to see itself as beer’s spiritual home, those are the only three ingredients it may contain – the yeast that converts the sugars in the barley to alcohol being out of sight and out of mind back then.
Today’s craft beer revolution takes such strictures less seriously, with new and exotic brews catering for all manner of tastes. But one ingredient remains a constant – indeed the fulcrum – of good beer. Hops give beer the bitterness that counterbalances the sickly sweetness of the fermenting grain and imparts subtle flavour tones that distinguish one brew from another, all while acting as a natural preservative.
That is reason enough to declare the hop one of the world’s most important, if often overlooked, plants. Yet trouble is brewing, with a perfect storm of changing tastes and changing weather contriving to shake up its cultivation. The question frothing on many a lip now is whether an ale and hearty future for the hop can be assured.
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Hops weren’t always so universally beloved. In England, they were once dubbed the “wicked weed”, and traditional ales were brewed without them. It is a , although the city of Norwich did in 1471, as it tried to defend the purity of yeoman English ale in the face of perfidious hopped continental imports. Before hops became the brewer’s undisputed best friend, all manner of botanicals were employed to flavour beer (see “Rooted in history“).
The hops that are used in beer are the flowers, or cones, of the hop plant, Humulus lupulus. Perennials that can live for decades, these are twining “bines” – plants that grow by spiralling in a helix around a support – that can reach some 5 metres up wires in hop fields or ramble through hedgerows. Compounds called alpha acids in the hop cones produce their characteristic bitterness, but other constituents, such as beta acids, essential oils and flavonoids, mean hops can also add citrus, grassy, floral or earthy flavours.
The recent boom in highly hopped craft pale ales has only made the plant more important. “Hops pull an extraordinary amount of weight for our beers,” says Thomas Nielsen, research and development manager at the Sierra Nevada Brewing Company in California and president of the US-based . “I like to think it is the hops that are differentiating these products more than anything else.”
But not all hops are born equal. Different varieties with picturesque names like Fuggles, Goldings, Citra, Hallertau and Saaz impart their own distinct degrees of bitterness or complex aromatics. Each prefers slightly different growing conditions. Then come the effects of local climate, soils, microbes and processing, together known as terroir, which brings subtle taste differences to hops, just as it does to a fine wine.
“Terroir is very important,” says Ali Capper, a hop grower and director of the . The UK’s mild maritime climate, for example, means hops have lower levels of a compound called myrcene, leading to beer with a more complex, delicate aroma. Those subtle differences can disappear in a bitterer beer, such as US-style pale ales. The UK brewing industry’s increasing reliance on imported hops, rather than local varieties, to satisfy changing tastes is one reason why buying a round of beers in a London pub .
But such developments are mere foam on the body of the problem. For all their ubiquity in beer, hops are particular about where they grow. “It’s not a crop for the faint-hearted,” says Capper. They need deep, high-quality soil, windbreaks to give shelter and plenty of moisture – but not too much, because that rots their roots. They are also highly sensitive to light. Flowering is triggered by the shortening of the days after midsummer, with the cones harvested in late summer. As the days close in further, the plant goes into a resting phase, dying back and storing food reserves in its roots for the next season. Without adequate cold over winter to encourage dormancy, growth during the following spring can be weak and unsynchronised.
This is why commercial hops are grown only in specific areas within a temperate “Goldilocks zone” between about 35° and 55° north. This includes the Pacific Northwest heartlands of Washington, Oregon and Idaho, which together account for about 40 per cent of global production, and areas of Germany, the Czech Republic and the UK. There is also some cultivation of hops at similar southern latitudes, in places like New Zealand.
It is also why climate change gets hop growers particularly hot and bothered. “No matter who you are or what you think, I don’t think anyone in the industry is unaware of the climate situation,” says Nielsen. In 2018, that severe droughts and extreme heat could lead to hop shortages, causing the price of beer to shoot up still further.
We are already seeing the first bit. In recent years, droughts in central Europe and the north-western US have hit hop harvests. “Hops are competing with Seattle and Vancouver for water from the mountains,” says Capper. In 2020, a significant chunk of the Pacific Northwest crop was destroyed by intense wildfires in the region, or had to be rejected because smoke had tainted its flavour.
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It isn’t panic stations quite yet: covid-19 lockdowns reduced demand so much that there was actually a . Many brewers also keep stores of hops that can last for years with the right care. But with conditions in traditional hop-growing areas predicted , the fear is that changes in climate and weather could alter the taste of the hops, their vigour or even, perhaps, wipe them out entirely in areas where they have grown for hundreds of years.
According to , a plant scientist at North Carolina State University in Raleigh, one effect is that nights are warming faster than days as global temperatures rise, reducing the number of winter nights where the temperature drops below freezing. This potentially influences the hops’ crucial dormancy period and gives pests such as insects, bacteria and fungi more time to grow and attack plants. That can also affect hop flavour: some of the hoppy smell of beer comes from antimicrobial compounds produced by the plant as a defence against attackers.
One response is to create new, climate-resistant hop varieties. The breeding programme at Wye Hops in Kent, an English county that is a traditional centre of hop growing, is looking at between 3000 and 4000 varieties to find ones that will thrive in different conditions – for example, coping with milder, wetter winters and hotter summers. But there are limits to how far that goes. “No [hop] plant likes sustained heat of two or more weeks of 30°C plus,” says Capper.
Similar projects are under way in the US, says Doherty – as are more dramatic initiatives (see “Beer goes south“). But Capper for one thinks there may have to be a more fundamental rethink of hops’ native territories. The UK should be OK, she says, as should New Zealand, because their maritime climates are less likely to see stark changes. But “I worry about Washington state, Oregon and Germany in terms of climate change,” she says.
Hop growers may have no choice but to up sticks. “Michigan now has a small hop-growing area. The whole northern hemisphere industry is likely to go north” to Alaska and Canada, according to Nielsen – and also to extend its range in Australia and New Zealand in the southern hemisphere.
This wouldn’t be unprecedented. While the European heartlands may have been pretty much unchanged for hundreds of years, “the US hop industry has a history of moving to get away from disease and pathogens”, says Nielsen. “One hundred years ago, it was in upstate New York; 70 years ago, it was in California; 30 to 60 years ago, it moved to the Pacific Northwest. There is no guarantee it will stay there,” he says.
That was mainly to escape mildew, a fungus that, once established in a hop-growing area, is nigh-on impossible to get rid of. Will climate change prove to be a more implacable foe? We can only hop for the best.
BEER GOES SOUTH
Launched in June 2021, Gator Pale Ale is brewed . So far, so US craft beer – only these hops were grown exclusively in Florida.
This was a far from trivial exercise, says , who led the work. Hops are delicate flowers (see main story). “The high temperatures and hurricanes in Florida aren’t ideal,” he says. There also isn’t enough of the daylight that is crucial during the summer months for hop flowering, which Agehara’s team got around by attaching LED night lights at the top of the hops’ support poles.
That isn’t an entirely new idea: South Africa, another country outside the hop-producing “Goldilocks zone” in temperate mid-latitudes, also grows .
Florida’s climate had other unexpected effects. Rather than a single crop of hop cones each year, there are two, one appearing from February to June, the next from June to November. The two crops together come to about 90 per cent of the average annual yield in the hop-growing heartlands of the Pacific Northwest. That’s a boon, but most importantly the beer proved popular: punters described a pleasant, melon-like aroma.
ROOTED IN HISTORY
The long history of flavouring beer with hops is just froth compared with how long we have been brewing: evidence of alcoholic drinks made from fermented grains dates back some 13,000 years. The , by contrast, is from just AD 736 in what is now Germany. Before that, to give their drinks flavour, ale brewers used , a mix of bitter herbs, flowers or roots, including dandelion, burdock, sweet gale, mugwort, ground ivy, yarrow, horehound and sage.
In the UK, hopped beer was probably first imported to Britain from the Low Countries in about 1400, and battled it out with native, unhopped ale for more than 100 years until a combination of taxes and laws gave hops the upper hand, turning ale and beer into synonyms.
One theory for the introduction of the Bavarian Reinheitsgebot, or purity law, of 1516 that mandated the use of hops in beer – and similar decrees in other parts of the Holy Roman Empire – was that gruit herbs were also used in pagan rituals.
The real breakthrough for hops, however, was probably the discovery of their preservative function: unhopped beer can go off in weeks, but boiling the hops before their use in the brewing process releases bitter, preserving resins that allow hopped beer to last for years.
Today, we have other preservatives – and . More beers are now flavoured by botanicals other than hops, and an annual International Gruit Day is celebrated on 1 February, as more and more people go back to the roots.
