Inside the Beltway

Future or Fiction: Pretty in Pink

Environmental science professor Michael Alonzo on DC's famed cherry blossoms 


Michael Alonzo

Q. On average, DC’s cherry blossoms achieve peak bloom on April 4. But on the heels of the city’s third warmest winter on record, they peaked this year on March 23—the fourth earliest date in 20 years. Will DC continue to be pretty in pink earlier in the year?
A. DC monitors tree phenology—the timing of plant life cycle events—more closely than most places because of our collective obsession with the Yoshino and Kwanzan cherry trees surrounding the Tidal Basin. In recent years, they have generally reached peak bloom stage earlier than in the past, with a seven-day advance in that date since 1921, though there is considerable year-to-year variation. 
We know that the climate is warming, and the consensus among scientists is that this causes plants in temperate regions to bloom earlier and frequently drop leaves later. The connection between climate warming and phenology is complicated though, so we’re not entirely sure what drives the earlier bloom date. It could be the warm spring, the insufficiently cold winter, or some combination of the two.

Will the date of peak bloom continue to advance? This is not settled science. It is likely that the date will come earlier for a time, but there are also counteracting forces that may slow this shift. For one, plants respond to photoperiod—the unchanging amount of light available on a given date at a given latitude. This cue helps early-blooming species to know what is too early and helps them to avoid frost damage. 
While we had a warm winter, March was relatively cold, which resulted in very early emergence of green buds, but a slower progression towards the pink blossoms everyone was waiting for.