But Rosemartin cautioned Alonzo against directly attributing the early bloom to climate change. “I wouldn’t say climate change caused the early spring,” she says. But climate change is loading the dice every year. We are more likely to get an early spring now than we were 30 years ago.
This is a somewhat consistent trend. In 16 of the past 20 years, the peak bloom has occurred earlier than the historic April 4 date. This average has been exceeded in seven days since 1912, a gift from the mayor of Tokyo, the first cherry trees in the district. Since that year, the average temperature around the Tidal Basin has increased by 2.5 degrees.
“This does not surprise me. [peak bloom] This year it’s falling at the end of March,” Rosemartin said. “A lot of plants are dormant below 30 or 50 degrees Fahrenheit. Every day it gets a little bit warmer than that, so they collect heat.”
But the phenological relationship is complex, she added. Mild winters don’t always produce early blooms. “If you don’t get a winter cold, you can be late,” she said.
The district’s variable weather conditions have not gone unnoticed as residents flock outdoors to enjoy the warmth and vibrancy of spring. “It’s the first weekend in March, and I’m wearing something winter weather-wise,” said longtime resident Chris Yates, who is in his mid-forties.
“It seems universally wrong,” he added, “but nowadays you say, ‘Oh, they’re beautiful trees.’
Reason for warning? It depends
According to Litterst, early sources are no reason to worry about the trees themselves. “They are a hardy species – they’ve seen extreme heat in the summer and extreme cold in the winter,” he said.
But with earlier blooms, there is a higher chance of late frosts occurring and damaging the blooms. “False sources are dangerous,” Rosemartin said. If it’s warm early, as it has been, still regularly a late frost or a big snowstorm comes and wipes out all the flowers.
That happened in March 2017, just as the trees reached peak flowering. Temperatures below 25 degrees Fahrenheit for three consecutive nights resulted in half of the trees losing their leaves.
This kind of cold snap could not only bring an abrupt end to the district’s pink and white scene, but also hurt local revenue. Washington’s annual cherry blossom festival, which runs from March 20 to April 16 this year, has generated more than $100 million in economic activity in recent years, according to organizers.
“When the trees bloom, people come down here, no matter what happens,” said Litterst of the park service. While early blooming is less likely to deter visitors, a lack of blooms can be disappointing, he said.
Cherry trees face the reality of sea level rise. The water level in the tidal basin is about 4 feet higher than it was when it was built 80 years ago, Litterst said. “We had to remove more than a dozen cherry trees because their roots could not take the constant flooding.”