How Do Trees Know When It’s Spring?

Apr 13, 2015

Video by The Atlantic

It’s a warm, sunny day in April, and all the trees are in bloom. But how did they know it was warm and sunny? And on a warm, sunny day in February, what keeps them from blooming? Scott Aker, a horticulturalist at the U.S. National Arboretum, tells Robinson Meyer how the process works and what to look for.