A species of bamboo widespread throughout Japan – Phyllostachys nigra var. henonis – is about to bloom for the first time in 120 years, then die.

Phyllostachys nigra var. henonis, sometimes called henon bamboo, is native to China but has been cultivated in Japan since the 9th century. It is one of the most common varieties of bamboo in Japan, which has approximately 1,700 km2 of bamboo forests. All bamboos are “monocarpic”: they flower once and then die. Some species of bamboo live for a few years before they flower, but many live for decades. Phyllostachys nigra var. henonis has an exceptionally long flowering interval of 120 years: the last major flowering of henonis was in 1908.

Because this happened so long ago, scientists don’t know how the plant regenerates. Researchers at Hiroshima University discovered a group of flowering henon bamboo as early as 2020. They took the opportunity to observe the germinating bamboo but have yet to solve the mystery. Although the plants produced seeds, none of them grew into new bamboos. “The bamboo did not produce any viable seeds that could germinate. Production of bamboo shoots stopped after flowering. There was no sign of regeneration of this bamboo after flowering for the first three years,” says lead author Toshihiro Yamada.

This suggests that bamboo is difficult to regenerate. However, as the researchers say in their paper, “this idea is clearly contradicted by the fact that this species survived for more than 1,000 years in Japan after its introduction from China.” Phyllostachys nigra var. henonis must have regenerated several times, as it surely experienced many flowering events during this period.

Researchers propose several hypotheses on the regeneration of bamboo, such as the existence of underground organs allowing the plant to regrow.

Meanwhile, this means that henon bamboo will take time to regrow after dying in 2028. “So a bamboo forest will turn into a grassland after flowering, for at least several years. We may have to manage this drastic change after the bamboo blooms,” says Yamada. “During the initial regeneration process, which will last at least several years, bamboo forests will clearly be unusable as sources of craft materials and edible bamboo shoots,” the researchers write.