But Rosemartin echoed Alonzo in warning against directly attributing the earlier bloom to climate change. “I wouldn’t say climate change caused the early spring,” she said. “But climate change loads the dice every year. We are more likely now than 30 years ago to have an early spring.”
This is a trend with some consistency. In 16 of the past 20 years, the bloom peak occurred earlier than the historical average date of April 4. That average is with seven days since 1912, when the first cherry trees, a gift from the mayor of Tokyo, were planted in the district. Since that year, the average temperature around the tidal basin has risen by about 2.5 degrees.
“I’m not surprised [peak bloom] falls at the end of March this year,” said Rosemartin. “Many plants go dormant below 30 or 50 degrees Fahrenheit. Any day it’s a little warmer, they accumulate heat.”
But the phenological relationship is complicated, she added. A mild winter does not always lead to earlier flowering. “If they don’t get their winter chill, they can be delayed,” she said.
The neighborhood’s changing weather patterns have not gone unnoticed by residents who have flocked outside to enjoy the warmth and vibrancy of spring. Chris Yates, a long-time resident in his mid-40s, said it was “weird in the context of, ‘It’s the first weekend in March and I’m hardly wearing winter weather.'”
“It feels wrong in an overall sense, but right now you just think, ‘Oh, they’re beautiful trees,'” he added.
Reason for alarm? It depends
According to Litterst, the early springs are no reason to worry about the trees themselves. “It’s a hardy species — they’ve experienced extreme temperatures in the summer and extreme cold in the winter,” he said.
But with earlier blooms, late frosts are more likely to occur and the blossoms will be damaged. “It’s the risk of a false feather,” Rosemartin said. “If it’s warm early, as it has been, there could still be a normally timed frost or a big snow storm that comes through and knocks all the blossoms off.”
That happened in March 2017, just as the trees were about to reach their peak. Three consecutive nights with temperatures below 25 degrees Fahrenheit resulted in the loss of about half of the trees’ petals.
Such a freeze not only brings an abrupt end to the pink and white spectacle in the district, but can also affect local revenues. Washington’s annual cherry blossom festival, which runs from March 20 to April 16 this year, has attracted more than 2,000 attendees $100 million in the economic activity of recent years, the organizers say.
“Once the trees bloom, there will be people here no matter when it happens,” said Litterst of the park service. While an early bloom is unlikely to deter visitors, he said, a lack of blossoms can be a disincentive.
The cherry trees are also facing the reality of sea level rise. Water levels in the tidal basin are about four feet higher than when it was built 80 years ago, Litterst said. “We’ve had to remove over a dozen cherry trees because their roots just can’t handle the constant flood of water.”