Washington, DC’s Cherry Blooms Draw Crowds—and Climate Questions

But Rosemartin echoed Alonzo in cautioning against attributing the earlier bloom directly to climate change. “I wouldn’t say that climate change caused the early spring,” she said. “But climate change is loading the dice every year. We’re more likely now than we were 30 years ago to have an early spring.”

This is a trend with some consistency. In 16 of the past 20 years, peak bloom has occurred earlier than the historic average date of April 4. That average has advanced by seven days since 1912, when the first cherry trees, a gift from the mayor of Tokyo, were planted in the district. Since that year, average temperatures around the Tidal Basin have increased by about 2.5 degrees.

“I’m not surprised that [peak bloom] is falling at the end of March this year,” Rosemartin said. “A lot of plants are dormant below 30 or 50 degrees Fahrenheit. Every day that it’s a bit warmer than that, they accumulate warmth.”

But the phenological relationship is a complicated one, she added. A mild winter will not always result in an earlier bloom. “If they don’t get their…