Here’s what Toronto’s cherry blossoms are telling us about climate change

Cherry blossoms captured at peak bloom on April 16, 2024, outside John P. Robarts Research Library. 

There’s a chance that if you were looking forward to seeing the cherry blossoms later this spring, you might be too late. Gone are the days when cherry blossoms were budding in May. Nowadays, the early stages of blooming can start in March.

Cherry blossoms, a symbol of spring in cities and towns across the world, have been blooming at earlier rates — well, at least in North America. If you happen to be a fan of seeing the blossoms, you’d better book some time to do so soon.

Blossoms in Toronto’s High Park are expected to be in peak bloom as of Monday, April 22. And the blossoms at John P. Robarts Research Library at the University of Toronto reached peak bloom on April 12. Usually, these blossoms can be sighted in late April to mid-May.

Cherry trees in Washington,. D.C., reached peak bloom in mid-March. Washington’s cherry blossoms typically bloom in the last week of March, making this year’s blossoms earlier than average by nearly two weeks. Due to changes in global temperature, it can be unclear when to anticipate blossoms for travellers.

Witnessing ‘peak bloom’

This was the case for Prof. Rowan Sage, who recently travelled to Japan and hoped to see its famous blossoms in person.

“They have had a cold spring here this year so the cherry blossoms are blooming much later and sadly, I will miss them by a week,” Sage said by email. “They are so late.”

Sage is not an expert on cherry trees, but he is a professor of ecology and evolutionary biology. As he tells his students, “This is just the beginning of climate change.” 

“With climate warming, we can expect earlier blossoming dates, with trees blooming on a pattern more akin to the Washington D.C. timetable,” he said.

When discussing cherry blossoms in the context of Toronto and other North American cities, it is important to look into their importance in the United States. In 1906, Dr. David Fairchild imported numerous cherry trees from Japan on his property located in Chevy Chase, Md. After years of advocacy from both the Fairchild family and Eliza Ruhamah Scidmore, an American journalist and travel writer who had travelled to Japan and fallen in love with the trees, 3,020 cherry blossom trees were gifted to the Americans from Japan. They were planted in Washington.

Following the popularity of the blossoms in the United States, Toronto saw its very first cherry trees in 1959. A Japanese ambassador to Canada made a donation of 2,000 trees to express gratitude for this country accepting relocated Japanese citizens after the Second World War. These trees were planted in High Park, along Bloor Street.

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According to the High Park website, buds on its trees were seen forming on Feb. 28. In previous years, Toronto would have been much too cold to see any signs of spring ahead. This early signal of spring within the blossoms can raise concerns about global warming. 

“Urban areas are a little bit warmer than surrounding landscapes so that may play a role in it,” says Danijela Puric-Mladenovic, an assistant professor at the University of Toronto’s Daniels Faculty of Forestry, and author of Predictive Vegetation Modeling for Forest Conservation and Management in Settled Landscapes

“If you get an early spring, (cherry blossoms) may bloom earlier,” said Puric-Mladenovic. “It has been changing from year to year so it is very sensitive to the weather.”

The link between climate change and early flowering

Since 2014, Toronto’s High Park has recorded peak bloom throughout April and May. The median average date of the peak blooms within the last 10 years is May 2.

Dates of peak bloom at High Park from 2014 – 2023 by Faryat Tabassum

Bar chart representing the speed at which “peak bloom” was reached over the past 10 years. Data from the High Park Nature Centre.

Associate Dean of Research Sean Thomas also teaches at the Daniels Faculty of Forestry. “There is a very strong climate change signal that is associated with early flowering, usually quantified in terms of degree days above a threshold temperature,” he said via Zoom.

“We’ve accumulated a lot of degree days, in this kind of year without a winter.”

Thomas warned of the dangers of early flowering.

“The immediate downside of [early flowering] is that, when you have cherries beginning to blossom in mid to late March, that’s well within the time you expect to have frost.” 

This means that the lifespan of cherry blossoms could be reduced by early flowering, due to weather conditions of the earlier months. Blossoms could fall at a faster rate, or perhaps be stunted in the early stages of their growth, resulting in no peak bloom for the season.

Early blooming in Toronto delayed by sudden snowfall

That’s exactly what seemed to be happening this year. Reports around early blossoming were swirling around as the temperatures in the city were fairly warm, causing the blossoms to go into their early stages of bloom. However, with the inconsistency between warm temperatures and sudden snowfall, the blossoming process had been delayed. 

Fortunately, the snowfall within the past few weeks was not harmful enough to stunt the growth of the cherry blossoms this year and they continue to grow. There is, however, a possibility that snowfall can cause the petals to freeze beyond recovery. 

“If there is a hard frost, cherry blossoms will be killed,” Thomas said. Low temperatures could cause “catastrophic loss of reproductive outcome” in blossoms for the year, he added.

There are six total stages in the cherry blossom timeline. As of April 16, The blossoms at High Park are at “Stage 4” of the bloom development process. This means the florets are exposed and you can see the light pink colour of the petals peeking through. 

High Park is one of Toronto’s most famous places to view cherry blossom trees. There are also trees at Trinity Bellwoods Park, Robarts Library, Edwards Gardens and other locations throughout the city. 

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Posted: Apr 18 2024 10:04 am
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