Like all grasses, bamboo goes through a flowering and seeding cycle. Most grasses do this each year. Temperate running bamboo does this, on average, about every 80 years or so. Some bamboos haven't flowered since they've been keeping scientific records, for over 200 years.
Bamboo flowering is something scientists still don't fully understand we usually can't predict when it will happen. There are some thing we do know, though. Even those a single grove, a single culm, or even a single branch can go into flower at any time, the most common method of flowering for most species is called a gregarious flowering, where an entire species, or at least a single clone, will flower all around the world at about the same time.
Since in the United States we don't have a lot of clonal diversity of many of our species, this essentially means that an entire species will go into flower at around the same time, generally in a time frame of about five years. There is some evidence to suggest that gregarious flowering isn't contained only to a single clone but often multiple clones within a species.
When a temperate running bamboo flowers, it concentrates most of its energy on creating flowers and seeds and therefore produces little vegetative growth. It is common for smaller groves or potted plants to die completely before the cycle is complete. Larger established and healthy groves will usually recover, but it can sometimes take a decade or more.
The seeds produced by flowering usually have low viability with low germination rates and are sometimes completely sterile.
Since we have so many species at our nursery, we always have several that are in flower. We remove them from their normal rows and put them all together, hoping for some possible cross-pollination, but we have never made the time to try to collect and germinate seeds so I am unsure if this even works.
What should you do if your bamboo if flowering? It depends. If it's a larger grove that is established, it is recommended that you fertilize and water so that it has as many nutrients as possible to make a full recovery. If it is in a container, I can say the best possible scenario is that it will barely survive after 3~5 years of flowering and will look almost-dead most of that time. I recommend replacing it.
Since we never know when bamboo if is flowering, it is not something we can guarantee or warranty against. When customers are making large orders of bamboo I usually recommend getting at least two species to guard against flowering. The chances of two unrelated species flowering at the same time is indeed very small.