Neelakurinji: The flowers that bloom once in 12 years

Neelakurinji or Strobilanthes kunthiana are inhabitants of Shola forests in Western Ghats. These plants blossom after 12 years exhibiting the gregarious flowering habit. The flowers of Neelakurinji are purple-blue in colour and it is because of these, the Nilgiri hills (blue mountains) got its name. The angiosperm belongs to Acanthaceae family with genus Strobilanthes. The genus has around 250 species, most of which show unusual flowering patterns. 46 species of the genus are found in India.

Neelakurinji is also found in Shevroys in Eastern Ghats. In ancient Tamil literature, kurinji flowers symbolize love. It was first described by the German botanist Gottfried Daniel Nees von Esenbeck.

Plants which bloom after long periods are known as Pletesials. They are known to exhibit ‘gregarious flowering habit’, masting i.e. a mass seeding phenomena or synchronous production of seeds by plants after long intervals of time. These plants need a long time to prepare themselves for flowering. The period between two flowering season is known as Oscillatory period and is controlled by endogenous factors. Strobilanthes kunthiana is 30-60cms tall and is found at altitudes ranging from 1300-2400m above sea level.

Plants are formed from specific region of stem cells called meristems which differentiate into shoot apical meristems and root apical meristems. In most plants which flower once, the shoot apical meristems get converted into floral meristems. After flowering, the floral mersitems stop growing as most of the energy and resources is devoted to mass-flowering. Thus, this results in senescence after the fruit set and production of seeds. The next bloom takes a long time as it has to go through the same cycle and gather as many nutrients again.

Neelakurinji flowers when the concentration of floral inhibitors falls and the florigens such as gibberellins act along with  more nutrients after phytochromes give the signal to do so. The meristems then produce floral buds which induces flowering. Flowering results in production of fruits and seeds which bring about physiological changes in the plant which trigger death.