Bamboo plants typically spread by sprouting from the base of the clump - in effect 'cloning'. But, similarly to any other grass-like plant, they also flower and produce seeds. In many bamboo species this takes place at around 20 - 50 years, after which the entire 'grove' dies.

It's been documented many times – over several centuries - that this very long flowering cycle often occurs in the same species of bamboo in many different areas in the same year. Some species even flower in the same year when growing on entirely different continents.

There are two unexplained factors with this phenomenon.

Firstly, why is the flowering cycle so long? One species - Phyllostachys bambusoides - has a flowering cycle of 130 years. There is no explanation as to why this trait has developed over evolutionary time. (Note that for shorter cycles, there have been suggestions that the trait may have evolved so as to prevent excess build-up of animals which feed on the seeds - but this clearly can't explain a cycle of 130 years.)

The second factor is regarding the botanical mechanism which somehow creates a month-accurate 130 year 'timer' within the plant. There are currently no plausible suggestions for how this might be happening.

Further reading : Annual Review of Ecology and Systematics 1976.7:347-391