We know the UW’s iconic Yoshino cherry trees typically bloom March through April, but forecasting the precise dates for visitors is an annual challenge. Now a UW research group is using historical temperatures dating back to 1966 and student-collected observational data to predict the timing of peak bloom — and looking at how a warming climate impacts that date.
In this video, UW News talks with doctoral candidate Autumn Maust about the surprising results of a study to be published this year. “What we found in Seattle is, because our winters are so mild and warm, there’s actually been a delay in the bloom time over the past six decades,” Maust says. “The bloom time is shifting later” — about two days per decade.
The reason has to do with cherry trees needing both chilling and warming units of time — accrued over winter and springtime periods of cool and warm temperatures — to reach a threshold that forces them through the bloom stages. Mild winters, Maust says, slow the chill unit accumulation times. She notes that other studies conducted globally have found that blossoms are blooming earlier, likely due to warmer spring weather. “The main takeaway from this study is that tree phenology and the time it takes to move through bloom phases is very dependent on localized weather data.”
When will the trees hit peak bloom this year? Stay in the know with our Bloom Watch, which is updated regularly to reflect the current blossom phases.