When do cherry blossoms bloom? B.C. contest aims to predict the peak

A cyclist rides past cherry blossoms in Vancouver, on Sunday, April 25, 2021. THE CANADIAN PRESS/Darryl Dyck

A contest organized by a B.C. university that aimed to predict peak bloom of the beloved cherry blossom drew dozens of participants from four continents.

Elizabeth Wolkovich, associate professor of forest and conservation sciences at the University of British Columbia, said she and her colleagues had the idea to get the public involved in figuring out when the short-lived seasonal favourites bloom.

"Cherry blossoms are an early spring species, they change a lot with warming and recently we've noticed that we're having trouble accurately monitoring the change," Wolkovich told CTV News Vancouver.

"With climate change we know that most temperate plants, especially in the northern hemisphere are advancing their leaf out and their flowering with warming. Some plants have advanced two or three weeks."

The contest looked at cherry blossoms in Vancouver; Washington, D.C.; Kyoto, Japan; and Liestal-Weideli, Switzerland. Eighty-one participants signed up, forming 41 teams.

"We have only so many ideas and concepts amongst us and so we thought if we could get the public and lots of additional researchers, citizens out there monitoring change, we might be much better able to understand what's going on with cherry blossoms and better predict them in the future," Wolkovich said.

Wolkovich explained cherry blossoms, like other temperate, woody plants, require cold in the winter followed by enough spring warmth to trigger flowering. She said some contestants used this classic biological pattern to make their predictions, while others used artificial intelligence like machine learning for theirs.

Results from the contest will be released in May. Wolkovich said the average predicted peak bloom date for Vancouver and Liestal-Weideli is April 2. In Kyoto, the average predication is April 3 and for Washington, D.C., it's April 1.

"This is absolutely critical for us," Wolkovich said. "How long the growing season is, how early these cherry blossoms start, is indicative of how lots of other early trees leaf out and that in turn determines how much carbon our forests take up and so ultimately this could inform and improve predictions of climate change."  

The contest is expected to run again ahead of next spring.