Climate change is causing Japanese cherry blossoms, a famous symbol of spring, to burst into peak bloom early. From Tokyo to Paris and Washington DC, nature’s calendar has been disrupted by unprecedented warm weather that could ultimately prove detrimental to one of the world’s most admired flowers.
A marker of seasonal change, cherry blossoms are profoundly symbolic in Japanese culture – representing both rejuvenation as well as the fleeting beauty of nature.
The centuries-old tradition of hanami – “flower viewing” – has been adopted in many countries, with crowds gathering for yearly scenic picnics beneath the fragrant pink sakura.
Forecasting the annual bloom is important business in Japan. Since 1955 the weather agency has calculated the precise moment of peak flowering for the 84 cherry tree hotspots up and down the country.
A tree is deemed to be blossoming once five or six flowers have opened. When 80 percent of it has flowered, it is in full bloom.
Blooming early
The average blossom start date has moved forward by 1.2 days per decade since Japan began keeping records in 1953, said Daisuke Sasano, a climate risk management officer at the Japan Meteorological Agency.
Between 1961 and 1990, cherry trees in Tokyo on average began blossoming on 29 March – but that date moved up to 24 March between 1991 and 2020.
Last year’s blossom in Tokyo began on 14 March – the earliest on record. Sasano puts this down to “global warming compounded with urbanisation”.
Over the past century Tokyo has warmed by 3C.
The biggest threat to the trees, however, are not springs that are too hot – but winters that are not cold enough.
“This is because the winter frost signals to the cherry trees that it’s time for them to wake up and start preparing their buds for spring,” Sasano said.
“Without this cold trigger, the cherry trees will spend the entire winter sleeping. Then in spring they will not flower because they have no buds.”
Fear of frost
Some 11,000 kilometres away, in Washington DC, cherry trees are also an iconic part of the springtime cityscape. Three-thousand sakura were given to the US capital as a gift of friendship from Japan in 1912.
On 17 March, the trees saw their second-earliest peak bloom on record – flowering almost a week before they were expected to.
Early blooms make cherry trees vulnerable to sudden cold snaps, which still happen despite the overall warmer spring temperatures.
The last major incident was in 2017, when half of DC’s Yoshino blossoms were lost due to a late frost that came in the middle of March.
This year's peak bloom happened so soon that it preceded the official start of DC's National Cherry Blossom Festival on 20 March.
From December to February the entire northern hemisphere notched up its warmest winter on record – reducing the exposure to the sort of cold weather a tree requires during its winter dormancy in order to be able to wake up and flower.
Christmas buds
Disconcerted by the milder conditions, some wilful cherry blossoms burst open over Christmas in France’s Maulévrier Oriental Park, home to Europe’s largest Japanese garden.
"That's really not normal,” head gardener Didier Touzé told RFI, adding that those flowers were then damaged by ensuing frost.
Despite the startling discovery, Touzé hasn't observed any major fluctuations in bloom dates over the years in the garden, which has drawn in tens of thousands of visitors every spring since its first hanami festival in 2017.
Errant blossoms aside, the trees' normal bloom still took place in March – albeit about a week early. Touzé said another variety of cherry tree is on track to bloom in April, its normal flowering period “give or take a few days”.
Organisers of the park's annual hanami are toying with the idea of starting the event a little sooner to account for potential early blooms.
"But the risk is that we'll then end up having a colder winter followed by a later bloom – so we won't have gained anything," Touzé said.
