By Krystal Laymon
When I moved to the District of Columbia last spring, I couldn’t wait for the roughly 3,750 cherry trees surrounding the Tidal Basin and many of our major national monuments to burst into bloom. Tourists and residents flock to the area every year to hurriedly snap a few photos, because these beautiful flowers have a short life cycle with a peak bloom of only a couple of days.
The bloom schedule of the cherry trees, like most plants, is phenological, which means that the timing of their bloom is dependent on the conditions of their environment. While the East Coast has experienced colder-than-normal temperatures and several inches of snow late in the season, it has not deterred this year’s cherry blossoms from blooming.
In fact, over the past 90 years, the cherry blossoms have actually been blooming earlier. The figure below presents data from the National Park Service that shows the annual peak bloom date – when 70% of the blossoms are in full bloom – for these cherry trees from 1921-2014. Look at the black line that helps to show the trajectory of change in that peak bloom date over time. It shows that, since 1921, peak bloom dates have shifted earlier by approximately 5 days. This is due to in part to increasing average seasonal temperatures, particularly in March, over this time period. The Washington Post even performed a local temperature analysis in 2012 which showed that “Washington’s average March temperature has warmed 2.3 degrees in the last 90 years.”
Tracking cherry blossom bloom trends isn’t just important for scheduling the District’s annual Cherry Blossom Festival. Indicators of the start of spring, like leaf and bloom dates, will become increasingly important for determining how climate change may affect seasonal patterns, and for tracking related impacts on ecosystems and natural resources.
This March in DC, we’ve experienced some cold sweeps, and as a result this year’s projected peak bloom date of April 11-14 is later than expected. However, this short-term blip belies the longer-term pattern of longer growing seasons and earlier bloom times – which is a key concept to understand when it comes to climate change. Year-to-year, seasonal occurrences such as bloom times or thaws may vary widely, but the long term trends tell the real story — and this national treasure is telling us by opening its petals, and blooming.
Peak Bloom Date for Cherry Trees Around Washington, D.C.’s Tidal Basin, 1921–2014
Data source: National Park Service, 2014
About the author: Krystal Laymon is a former ORISE Fellow in EPA’s Climate Change Division. She has a background in environmental policy and communications. Krystal received her Master in Environmental Science and Policy at Columbia University and currently resides in Washington, DC with a turtle named Ollie.
National Park Service. 2013. Bloom schedule. Accessed December 6, 2013. www.nps.gov/cherry/cherry-blossom-bloom.htm.