Somei-yoshino: one cultivar, different flowering dates

Clusters of usually five-petalled flowers have stalks connecting them to the branch. New foliage is not yet prominent at peak flowering. Petals, stalks, calyces and developing leaves together provide stronger identification than pink colour alone.

Genetic research connects the cultivar’s main ancestry with Edo-higan and Ōshima cherry. Grafting or cuttings preserve the selected genotype. Self-incompatibility within the clone does not prevent fruit after pollination by genetically different trees. Seedlings are offspring with new genetic combinations, rather than copies of the original clone.

Nurseries and domestic planting

Nurseries around Somei participated in its sale and spread around the end of the Edo and beginning of the Meiji periods. Fujino Yorinaga attached the Somei name in 1900 to distinguish it from the cherries of Mount Yoshino. Grafted trees spread through later planting. Genetic parentage alone cannot identify a particular breeder or the exact event that produced the first plant. Hirosaki Park offers a local planting history: the city’s chronology records one thousand cherries in 1882, another thousand in 1901–1903, and thirteen hundred Somei-yoshino in 1956. The present landscape reflects successive planting campaigns rather than one founding moment.

Commemoration and international exchange

Planting also served commemoration and exchange. Mie Prefectural Museum identifies Emperor Shōwa’s enthronement and postwar reconstruction as occasions for planting Somei-yoshino. Its account of Kairaku Park traces a different transition: trees brought from Somei to a lord’s late-Edo villa became part of a public park after the Restoration. Overseas planting depended on nursery work too. Tokyo’s 1912 gift to Washington contained 1,800 Somei-yoshino among 3,020 cherries, grafted from Arakawa scions onto rootstocks raised in Itami. In 1952, after wartime decline in the original Arakawa grove, the United States sent budwood from the descendants back to assist restoration.

The Japan Meteorological Agency uses five or six open flowers on a designated cherry tree as its opening threshold and roughly eighty per cent or more for full bloom. Other cherry types substitute in parts of Hokkaidō and the southwestern islands. A reported date belongs to the observation tree, not every tree in the city.

Flower buds first become dormant. A sufficient period of winter chilling releases their internal dormancy; subsequent warmth supports development towards flowering. These are different stages: a mild winter can delay dormancy release even as warmer conditions later speed development. Local growing and management conditions also matter. Clonal trees need not flower simultaneously. A frequently repeated sixty-year lifespan is not a biological ceiling for every individual. Hirosaki applies experience from local apple cultivation to pruning, fertilisation and pest management, and formed a dedicated sakuramori care team in 2014. Continuing care helps explain an old tree’s condition alongside its planting date.