RENEE MONTAGNE, HOST:
In Washington, D.C., you could say the primary colors are red and blue, but this weekend, the nation's capital was awash in pink and white.
DAVID GREENE, HOST:
Yes, indeed. Tens of thousands of people descended on the city for the final day of the Cherry Blossom Festival just as the trees hit peak bloom. The National Park Service is pretty good at figuring out when the trees will look their best thanks to a little inside information.
MICHAEL STACHOWICZ: We are looking at the indicator tree.
GREENE: That's Michael Stachowicz from the National Park Service. He was standing under a Yoshino cherry tree, steps away from the Jefferson Memorial and the Tidal Basin. It's one of the originals given to the U.S. as a gift by Japan back in 1912.
STACHOWICZ: This tree right here blooms, for whatever reason, a week earlier and always has.
MONTAGNE: The indicator tree got its nickname because it is incredibly accurate in predicting when the colorful display of the blossoms will reach their peak. This year, it was a bit tricky. February and March were colder than usual in Washington, then, all of a sudden, it warmed up.
GREENE: And when the mercury finally rose, Stachowicz says it was like hitting nature's fast-forward button.
STACHOWICZ: Once we get some temperatures, they really start rolling and the floras extend. We get peduncle elongation.
MONTAGNE: For the non-horticulturalist, peduncle elongation is when the buds start looking like little asparagus spears about six to 10 days before peak bloom. Predicting the bloom each year involves watching those biological clues, along with the weather forecast and historical data. But the Park Service's Mike Stachowicz says those calculations don't take away from the experience of seeing all those cherry trees in bloom.
STACHOWICZ: It's just cool. It doesn't change how I look at it. It's still magical. When they bloom, it's still beautiful, you know? And the numbers kind of go away when you start to see the blooms come out. Transcript provided by NPR, Copyright NPR.