Editor’s Note: This article previously appeared in a different format as part of The Atlantic’s Notes section, retired in 2021.

It’s here! Sunday marked the beginning of spring season in the Northern Hemisphere. Last year, Rob asked a horticulturalist at the U.S. National Arboretum how trees know when to bloom:

Some of America’s most famous spring-bloomers? The cherry blossoms of D.C. The National Park Service’s “Bloom Watch” says we just started the period of peak bloom:

The peak bloom date is defined as the day when 70% of the Yoshino Cherry (Prunus x yedoensis) blossoms are open. Peak bloom varies annually depending on weather conditions. The most likely time to reach peak bloom is between the last week of March and the first week of April. Extraordinary warm or cool temperatures have resulted in peak bloom as early as March 15 (1990) and as late as April 18 (1958).

Andrew built a tracker to guide Washingtonians to the nearest cherry tree:

For those of you not in the area, you can awkwardly watch the grass—erm, trees—grow on this live webcam. If that’s not enough spring-spiration, Alan assembled photos of the season from around the world.