8 Oct : When bamboo flowers it dies! Anyone familiar with bamboo has probably heard this. Although this sometimes happens, it is not inevitable. This phenomenon can often be an opportunity in disguise to Flowering-Prediction of Death.
Flowering in bamboo is a botanical enigma. The factors that switch a bamboo plant from vegetative to flowering state are not fully understood. Nearly all species of bamboo seem to have their own life histories. Some species outside of the Indian-Asian tropics, and a very few in these tropics, have populations composed of individuals that grow to maturity and then flower and seed annually for many years. The culms that flower often die after the fruit has developed but other culms and rhizomes survive and perpetuate the stand. Many of the more common Indian-Asian species have populations made up of individuals that seed synchronously at regular and long supra-annual intervals. After growing by rhizome and branch production for a species-specific period of 3-120 years, nearly all the members of one species in one area produce wind-pollinated flowers, set large quantities of seed and die. This seed germinates immediately or when the first rains come.
According to their flowering habits, there are three types of bamboo: (i) those that flower annually or nearly so, e.g., Arundinaria spp. in India and Schizostachium brachycladum in Thailand; (ii) those that flower gregariously and periodically; (iii) those that flower irregularly. The flowering habit of Bambusa spp. and Dendrocalamus spp. in the tropical regions of Asia and of Phyllostachys and other genera in Japan belongs to types (ii) and (iii). P. edulis flowers sporadically, and the flowering occurs in small areas or in a few clumps. Periodical and gregarious flowering occurs in cycles; the cycles are more or less constant for a species in a given locality but differ between remote locations. Below are the flowering cycles of some Indian species:
Indocalamus wightianus, Ochlandra scriptoria, O. rheedii, O. stridula
Thamnocalamus falconeri, Chimonobambusa falcata
Oxythenantera abyssinica, Melocanna baccifera, Bambusa arundinacea
Bambusa copelandii, Pseudostachyum polymorphum
Phyllostachys bambusoides (120 years in
Although a wide range of research and discussion is going on, the flowering of bamboo is still unexplained and mysterious. There are several theories concerning the causes of flowering and death of bamboo:
1. Pathological theory, which postulates that flowering is brought on by the destruction of bamboo by organisms such as nematodes, fungi, insects and parasites;
2. Periodical theory, which proposes that the cycle starts with bamboo regeneration through asexual methods (rhizome and culm elongation), reaches maturity and results in flowering;
3. Mutation theory, which considers that bamboo regeneration through any methods of asexual propagation is mutation and brings about flowering of bamboos;
4. Nutrition theory, which proposes that flowering and fruiting are usually the result of a physiological disturbance arising chiefly from the poor growth of the vegetative cells, brought about by an imbalance in the carbon-nitrogen ratio;
5. Human theory, which states that human practices such as cutting and burning induce bamboo flowering.
It is generally believed that flowering in bamboo results in death of the bamboo. Subsequent to flowering, bamboos show the following types of mortality behaviour:
6. Flowering does not result in the death of either aerial or underground parts, e.g., some species of Arundinaria, Phyllostachys, Bambusa atra.
7. Flowering results in complete death of aerial parts only, the rhizomes remain alive and plants regenerate, e.g., Arundina amabilis, A. simonii, Phyllostachys nidularia.
8. Flowering results in complete death of aerial and underground parts and regeneration is only possible from seeds, e.g., Melocanna bambusoides, Thyrostachys oliveri, Bambusa arundinacea, B. tulda.
Many of the bamboos in cultivation were introduced as single propagules leaving us with but one clone of that species. There may be hidden in the genes of that plant useful characteristics that may of use to the grower. New seed grown clones may be more vigorous, more hardy, more resistant to disease or insects, or perhaps more ornamental. Who knows what new traits may be found. Few have the knowledge or skill to create bamboo hybrids. Efforts can be to grow new plants from seed. Clones with special characteristics are often not reproduced when grown from seed, so it is important to try to conserve them vegetatively.
Various methods have been suggested to revive flowering bamboo where some methods have been effective in some cases, many have not.
Flowering Bamboo Presents an Opportunity
Flowering bamboos do not always die; although many do — especially in the case of gregarious flowering. Even an individual plant that suspends growth of new culms and foliage for the exclusive production of flowers may die.
The phenomenon of gregarious flowering may involve many plants, but not necessarily all plants of that species or clone. Sometimes bamboo of a species growing over a large area may flower at the same time. Cultivated bamboo plants normally are of a single clone or closely related seedlings and there is a danger that all or most of a given type may flower and die. There are bamboos that do not flower and, therefore do not set seed. But these bamboos are not found growing in the wild. They are cultivated plants.
Since bamboo is anemophilous, wind pollinated, it must have many flowers at anthesis at the same time for successful spread of the pollen. The reason bamboos die after flowering is most likely so that the seedlings will receive the water, nutrients, room and sunshine that would otherwise be used by the mother. The seedlings are mulched by the debris of the dying parent. The mechanism for the timing of flowering and dying is a phenomenon not yet understood. It is one of nature’s baffling mysteries.
What should one do when a bamboo flowers? One option is to do nothing. The plant may recover, or it may die. Another option is one could collect seeds and start a new generation, or could also just remove any dead and dying culms to keep the planting from looking so unattractive. Some bamboos are destined to die when they flower, and growing from seed is the only way to save the bamboo. Another bamboo, Sasa megalophylla f. nobilis, a very attractive variegated bamboo flowered in the early 80’s and perished.
The best option is to collect some seed and try growing a new generation under a more controlled environment, and also work toward reviving the plant vegetatively. If the plant is flowering on only a few branches or culms, no intervention may be required. This could be the precursor of a more thorough flowering though. If the entire plant is flowering,cutting out flowering culms, fertilizing, and watering heavily may help
If the plant is large and in the ground,one can cut off any flowering culms and chop the rhizomes into sections with an ax where they are buried in the ground. This is followed by fertilization, watering and continuing care and it might recover.
There has been some research done on the flowering and rejuvenation of bamboo in China. Hsiung et al. (1981) report on experiments with P. vivax, which flowered in Jiangsu and Zhejiang Provinces from 1969 to 1976. Their method for fast rejuvenation was to dig up rhizomes (without culms) from the flowering stands and cut them into 30-50 cm sections. These were dipped in a 100 ppm gibberellic acid solution for 5 hours and then buried in a cutting bed. When new shoots emerged, they were sprayed with the solution every two weeks. After 3 months, 36% of the culms from treated rhizomes flowered, while 64% of the culms from untreated controls flowered. After a year, the treated culms produced more normal, non-flowering culms than the controls. Hsiung warns that nitrogen fertilizer does not necessarily stop the flowering of bamboo stands, sometimes it tends to retard their rejuvenation.
Some bamboos recover on their own after flowering while others may not recover vegetatively no mater what you do. The latter is more likely if the plant is small or weak at the onset of flowering, although even large and healthy, some bamboos such as Fargesias may flower and die no mater what you do. But like many generalizations, this does not always hold. Phyllostachys elegans at The Bamboo Garden has flowered sporadically every year for about 10 years while continuing to grow with moderate vigor. It, has not been restored to a vegetative, non-flowering state, by prune and divide strategy. It continues to flower and grow with no sign of stopping. Some species of bamboo seem to have a few plants in flower somewhere most of the time. In China there always seem to be some Moso plants flowering.