The Peculiar Mass Flowering Habits Of Bamboo

Bamboo flowering has been fascinating scholars and gardeners for centuries. More than just a natural curiosity, it has inspired fear and awe, and it’s still not fully understood by scientists. That’s because an entire bamboo species can live for many years, then suddenly flower at the same time and die off afterwards in spectacular fashion!

When more than half the bamboo plants in a grove bloom at the same time, it’s referred to as synchronized mass flowering or gregarious flowering. The phenomenon is usually followed by the bamboo plants’ death, which, on a large scale, can pose a threat to local economies and biodiversity.

Not all bamboo species bloom simultaneously, but the ones that do are also some of the most popular ornamental species. If you have a bamboo grove, learning about mass flowering can help you understand its causes, and whether it’s a risk for your bamboo garden. Read on to learn all about the peculiar mass flowering habits of bamboo!

Why does bamboo flower at the same time?

Many plants that we’re familiar with, from garden vegetables to decorative shrubs, are either annual or perennial plants. Annual plants flower and die by the end of one season, while perennial plants usually flower and grow back from woody growth year after year.

Bamboo, because it lives for many years, is technically a perennial plant, even though it usually only flowers once in its lifetime. Most bamboos flower en masse, and with periodicity, across an entire species. Scientists are not entirely sure what causes the mass flowering of bamboo, but they have a few theories.

Predator satiation

The most popular theory suggests that bamboo plants have mast years. They produce seeds in vast quantities in an attempt to overfeed local populations of rodents, birds, and other seed-eating animals. It’s impossible for animals to eat all this food, which means that the surplus will ensure that a new generation of plants can grow from the leftover seeds.

Improved pollination

Another popular theory suggests that, because bamboo is wind pollinated, it has evolved a gregarious flowering mechanism to increase its chances of pollination. If all the bamboos in one forest bloom at once, this makes it easier to spread and share pollen. This increases the pollination rate and improves local genetic diversity.

Increased seedling survival

Some scientists believe there’s a link between gregarious flowering and the fact that most bamboo species die after they bloom. It’s possible that the plants die en masse in order to provide better growing conditions for their seedlings.

If you’ve ever seen an old bamboo grove, you’ve probably noticed that it’s quite dark and dense, with not a lot growing under the canopy. The seedlings would struggle to grow and become established in such conditions. But if the mature culms died out, that would give the seedling better access to light and nutrients.

Complex mathematics

A recent study suggests that mass synchronized flowering is the result of something completely unexpected: bamboo plants are good at math. Harvard biologists believe that these plants use complex mathematical models to determine when to flower, in an attempt to synchronize pollination and seed production.

A genetically-transmitted phenomenon

One of the most fascinating things about bamboo is that each plant seems to have an ‘internal clock’ that lets it know when it’s time to bloom. The plant transmits that information to the seeds, but also every new cane or culm in that clump. When the time comes, the plants will flower at the same time, regardless of age.

The canes will remember when it’s time to bloom even if you remove them from the clump. This is why propagating cuttings from flowering bamboo plants is not recommended. When the clump or the ‘mother plant’ blooms, the plants propagated from it will bloom shortly after, even if they’re several decades younger.

Most nurseries use cane cuttings to propagate their bamboo. The process is cheaper and faster than using seeds. But, as clones of the mother plant, these plants also have shorter lifespans. Some bamboo nurseries will list the last flowering date of their plants to give you an idea of when you can expect them to bloom next.

Challenges with predicting bamboo mass flowering

Scholars have been recording the blooming cycles of bamboo since 813 A.D., proving the regular periodicity of mass bamboo flowering. But despite all the available data, it’s still difficult to predict when bamboo will bloom next.

Flowering cycles can be unpredictable for many reasons depending on the region and the plant’s growing conditions. Climate, geography, cultivation, and environmental changes can all shape or disrupt blooming patterns.

But the biggest challenge of all is time. Because there are often many years between the mass flowering of a species (sometimes over 100), it takes a long time to record multiple flowering events. Without records of at least 3 generations, it’s nearly impossible to predict the next time a bamboo might flower.

So while many species of bamboo do have a regular flowering cycle, keep in mind that it’s difficult to make accurate predictions for future flowerings.

Which bamboo species experience mass flowering?

There’s no clear relationship between mass flowering and bamboo genus. Perhaps it’s an unfortunate coincidence, but some of the most popular ornamental bamboos, like Fargesia and Phyllostachys, are also the ones most likely to bloom and die simultaneously.

This chart shows the flowering frequency for several bamboo species that flower gregariously:

Interested in other gregarious bamboo species not on the above list? Check out this resource (pg. 14+) and this one for more data on bamboo flowering habits observed around the world.

The ‘curse’ of the flowering bamboo

Although spectacular, mass bamboo flowering is considered bad luck in some parts of the world. It’s usually followed by the mass death of the plants, which can threaten local economies as well as natural biodiversity.

In northeast India, the phenomenon is called Mautâm, and it’s usually associated with an outbreak of rats attracted by the large quantities of seeds or ‘bamboo rice’. The outbreak is followed by a period of famine, disease, and loss of building materials for the locals. The people living in the Indian state of Mizoram even have a proverb about it:

“When the bamboo flowers, famine, death, and destruction will soon follow.”  

Similar rodent outbreaks followed by plague and famine have been observed in other parts of the world, including Hong Kong, Laos, Japan, Madagascar, and South America.

Gregarious flowering is also bad news for the giant panda, which relies on bamboo for 99% of its diet. The mass death of these plants creates food shortage and habitat loss for this vulnerable species, threatening its survival. For example, it’s estimated that almost 50% of the panda population in the Wolong Nature Reserve in China died as a result of the mass flowering of bamboo between 1983 and 1985.

Does that mean that you should be worried about bamboo mass flowering?

Not at all. 

Flowering is a normal part of the lifecycle of bamboo. It’s also a once-in-a-lifetime event. So if you have flowering bamboo in your garden, save the seeds, propagate them, and use the new plants to remind you of witnessing this mysterious natural phenomenon.

Have you experienced flowering bamboo? Do you have any other questions about the mass flowering habits of bamboo plants? Leave us a comment!