Tokyo odds-on favorite to see earliest cherry blossoms

TOKYO >> Weather companies have released their forecasts for the “cherry blossom front” — the advance of cherry blossoms across the country — which is expected to begin within days.

Traditionally, cherry trees begin flowering in warmer parts of Japan and gradually move northward. This year’s forecast for Tokyo, however, says the trees — known as sakura — could erupt into color exceptionally early, and some forecasters are even predicting that the capital will be the first part of the country to witness an explosion of pink. Tokyo is on Honshu island, located in the middle of Japan.

Weathernews Inc.’s forecast, released in mid-February, predicted cherry trees will bloom in Tokyo on Monday, along with Fukuoka prefecture.

Weathermap Co.’s forecast, meanwhile, suggests and even earlier bloom: Friday, again on the same schedule as Fukuoka.

Japan Weather Association predicts Tokyo sakura trees will bloom Wednesday — later than areas on the islands of Kyushu and Shikoku, but still the earliest expected date on Honshu, along with Hiroshima and other cities.

But how can this be, given that Honshu in nowhere near the southernmost area of Japan?

One reason for sakura flowering so early in central Tokyo could be the ages of trees sampled for the predictions, said a Weathernews spokesperson.

Japan’s Meteorological Agency bases its bloom announcements on sample trees in 58 areas across Japan’s 47 prefectures. When five or six flowers show up on a tree, the agency deems the sakura to be “in bloom.” When more than 80% of the buds unfold, it declares a “full bloom.”

The Someiyoshino cultivar is used to determine official flowering dates everywhere in Japan except Okinawa prefecture and the Amami region in southern Japan, and parts of Hokkaido in northern Japan. One caveat: Someiyoshino trees between 40 and 50 years of age tend to flower earlier than they did as younger trees.

“Older Someiyoshino trees no longer need to pour energy into growing their trunks and leaves. They can focus more on flowering and thus bear more flowers that bloom slightly early,” said Hiroyuki Wada, a researcher at the Flower Association of Japan.

The maintenance and health of individual trees are also factors, he added.

Tokyo’s sample tree is on the grounds of Yasukuni Shrine in Chiyoda ward. Its exact age isn’t known, but it was already mature in 1966, when it was selected as a sample tree, according to the shrine. To prevent the tree’s roots from weakening, the soil is softened and maintained to improve ventilation and drainage, which, in Wada’s opinion, leads to its early flowering.

“We observe cherry trees in the surrounding area, too, and those samples don’t necessarily bloom earlier than the others,” said another agency official, adding that it’s likely higher temperatures in large cities are a factor.

According to the meteorological agency, the average temperature in Japan has risen by 2.3 degrees Fahrenheit over the past 100 years, while in central Tokyo, it has risen by nearly 6 degrees. Tokyo has had the nation’s earliest bloom date six times since 1953, when statistics first became available, with four of those dates occurring after 2000. Some experts tie rising temperatures from urbanization to these flowerings.

However, the average March temperature in Tokyo during this period was about 49, lower than temperatures in Kagoshima (55) and Kochi (52) prefectures, indicating that temperature rise alone is not responsible for Tokyo’s early blooms.

“It’s true that the age of the trees and the rise in temperature are factors that hasten the trees’ blossoming, but the cold of winter can also affect the blooming period,” said Akira Kobayashi, director of the Japan Tree Doctors Association. “The reasons behind Tokyo’s early flowerings need to be carefully analyzed.”