It is not easy to miss Kerala’s State flower, the ‘kani konna’ or the Indian laburnum, when it is in bloom. Surprisingly, it has been found blossoming in several parts of the city since early January.
Laburnum trees, for instance, on either side of the Kaloor-Kathrikadavu Road have already painted the avenue yellow. But are these bright blossoms ahead of time?
In Kerala, the lore goes that laburnum ( Cassia fistula ) trees bloom in time for Vishu which falls in mid-April.
“People use the flowers to prepare ‘vishukkani’,” said K.S. Lyla, a teacher at Government High School, Kuttamassery, Aluva. “Because it is such an integral part of Vishu celebrations, people have noticed that many trees now complete flowering before Vishu,” she said.
Ms. Lyla is studying trees as part of SeasonWatch, a citizen science programme that documents the stages of flowering, fruiting, and arrival of fresh leaves of several tree species across the country. Under the project, one of the trees she and her students have been observing since 2017 is the Indian laburnum.
“This tree bloomed profusely in September, immediately after the floods. Now, there is not even a single bud. Maybe it will flower in April, but we don’t know,” said Ms. Lyla
Across the world, scientists have recorded a shift in phenology—the time of flowering, fruiting, and arrival of leaves—in several tree species with the rising air temperatures. In Germany, for instance, an examination of data from 1961 to 2000 showed that the phenology of fruit trees and field crops had clearly advanced as air temperatures had drastically changed since the late 1980s. Another study across Europe revealed that a warming in early spring (February to April) by 1 degree Celsius caused an advance in the beginning of the growing season by seven days.
SeasonWatch has been compiling citizen science data on several Indian trees since 2010 to study such trends for the country’s tropical trees. However, weekly data is probably not enough to comment on the causes of the early flowering of laburnum, said Geetha Ramaswami, coordinator of SeasonWatch. Lack of older data for comparison is also an issue, she added, though it may be possible to correlate changing temperatures with the phenology patterns in a few more years.
“But anecdotally and from long-term data [albeit only from a few trees], it appears that the pattern of finding most trees in full flower around the time of Vishu is definitely changing,” she says.
