The University of Toronto's St. George campus recently stepped into spring with the arrival of its delicate pink cherry blossoms while full blooms at U of T Scarborough were expected this week .
Dozens of trees have been planted on or near U of T's campuses as gifts from the Consulate General of Japan as part of the Sakura Project - but only after undergoing a few necessary tweaks.
Danijela Puric-Mladenovic, an assistant professor at U of T's Institute of Forestry & Conservation in the John H. Daniels Faculty of Architecture, Landscape, and Design, says that, in order to enable them to grow in our climate, local sakura is grafted on top of sweet cherry rootstock.
She points to a row of flowering cherry trees on Ursula Franklin Street on the St. George campus as an example.
"On one tree, a single branch is already in full bloom with white flowers," says Puric-Mladenovic, who teaches courses in landscape ecology, forest conservation and green urban infrastructure, among others. "This branch belongs to a sweet cherry, which serves as the rootstock onto which the Japanese flowering cherry was grafted.
"At some point, a branch from the rootstock began to grow and has since become part of the tree's canopy. Because it is genetically distinct, it blooms earlier and produces white flowers rather than the typical pink blossoms. It's an example of grafting and tells an interesting story about how different species respond to seasonal conditions."
Puric-Mladenovic's research and professional practice centre on forests within developed and urban settings. She focuses on creating practical tools and solutions that inform strategic conservation, restoration and integrated spatial planning of green infrastructure, vegetation and forest systems across urban and agricultural landscapes. In collaboration with Professor Emeritus Andy Kenney, she co-developed Neighbourwoods , a tree inventory and monitoring protocol.
Puric-Mladenovic says weather also plays an important role in bloom development. She says this year's spring brought out leaves at the same time as buds, which is atypical.
"In cooler springs, leaves have more time to emerge alongside the flowers, which can make the display appear less vibrant due to the added green," she says. "In contrast, a sudden warm spell rushes flower development, often resulting in a more intense burst of pink blossoms."
She also notes that not all Japanese flowering cherries bloom at the same time. She says there are many different cultivars, which are varieties that have been specially bred or selected, and each has its own timing.
"There are other cherry species on U of T campus, including our native Prunus virginiana - chokecherry - which typically blooms after its leaves have already developed. Some ornamental cherries, like 'February pink' or 'Accolade,' can bloom weeks before the more familiar Yoshino cherries. So, across Toronto, the cherry blossom season unfolds in stages rather than all at once."
Puric-Mladenovic says this past weekend marks the peak of the cherry blossom season in Toronto's High Park. In addition to the blooms on Ursula Franklin Street, more cherry blossoms can be found outside Robarts Library and along the pathways of the Landmark Project on U of T's St. George campus.
Meanwhile, the blooms between U of T Scarborough's Social Sciences Building and Humanities Wing are expected to peak in the next few days.
