The fate of ancient trees predicts cherry blossoms blooming in Japan

On March 19, the Japan Meteorological Agency (JMA) announced that the cherry blossom season began in Tokyo, after meteorological staff inspected standard trees at Yasukuni Temple. On March 23, JMA continued to confirm the start of flower season in Hiroshima, after recording the first flowers blooming on standard trees.

In large parks, crowds of people flock to enjoy the beauty of Somei-yoshino flowers, the symbolic flower of the land of the rising sun. Behind the bustling atmosphere of the flower viewing festival, experts are racing against time to preserve and replace old cherry trees.

To make accurate announcements about the start of the flower season (kaika) and when the flowers are in full bloom (mankai), Japan maintains a system of 58 “standard trees” across the country. According to regulations, only when the local standard tree blooms 5 flowers can the flowering season be officially announced.

The majority of these trees belong to the Somei-yoshino variety, planted in the 1950s. During post-war reconstruction and rapid urbanization, Japan greened its cities with cherries to reduce air pollution and mark new development milestones.

After more than 70 years of development, standard trees are entering the aging stage. Mr. Kobayashi Akira, a member of the Japanese Association of Plant Doctors, said that many ancient trees are experiencing a situation where there are few flowering branches, dry and broken branches, or even hollow roots leading to collapse. According to statistics, more than 40% of standard trees have had to be replaced with young trees within the past decade to maintain monitoring activities.

In Sendai city, a new standard tree will officially be used from this year. The old tree was planted in 1952 and has served monitoring work for more than 70 years. Two years ago, the tree contracted witches’ broom disease, causing branches to grow abnormally, reducing flowering ability and causing branch death, affecting the accuracy of observation.

In preparation, the Sendai meteorological agency planted two replacement trees 10 years ago in a location with similar lighting and soil conditions. After monitoring and comparing bloom data every year, the tree with the most similar index to the old tree was chosen as the new standard from December last year.

Currently, the flower buds on the new tree have not fully bloomed yet. Sendai people are waiting for the moment this new standard tree does its duty for the first time.

Besides JMA, many private meteorological units also participate in forecasting the cherry blossom season. Weathernews Company, Chiba Prefecture, uses data on average temperature, maximum temperature and sunshine hours to make predictions. This unit also mobilizes people to periodically send photos of flower buds to analyze the flower status in 7 stages.

This year, Weathernews launched a forecast service via mobile application. Artificial intelligence (AI) analyzed more than 10,000 flower bud samples to provide instant results when users provide photos. Last season, this service collected 55,000 photos.

Visitors can refer to NHK World’s online map. The map updates daily the flower status at more than 1,000 locations on 6 levels, from the time the buds appear until the petals fall.