Nature · Long read · 14 min read

Neelakurinji: The Twelve-Year Blue of the Western Ghats

A small shrub that waits twelve years to flower, turns whole mountainsides blue, feeds a season of bees and then dies. Its biology, history and culture, the wild flowers that share its hills, and the pressures that now threaten them all.

By GK Global, Adimali, Munnar · Trails & Tales by GK

For eleven years it is easy to miss. On the high slopes above Munnar it grows as a low, scruffy shrub among the grass and at the edges of the shola forests, its leaves rough and dull, unremarkable to anyone but a botanist. Then, in the twelfth year, every plant across a hillside flowers at once, and the mountains turn blue. Within months the flowers are gone and the plants are dead, leaving their seeds to begin the cycle again.

This is Neelakurinji (Strobilanthes kunthiana), the "blue kurinji", the most famous flower of the Western Ghats. Its last great bloom in Kerala came in 2018; the next is expected around 2030. This article looks at what the plant is, why it behaves so strangely, where it grows, the remarkable flowers that share its home, and the threats that, in 2024, led scientists to list it as a threatened species.

A plant that counts in twelves

Neelakurinji belongs to Strobilanthes, a large genus of shrubs in the acanthus family. Estimates of its size vary between sources, from about 250 to more than 400 species worldwide; India has around 150, and the great majority of these are found only in India, with the Western Ghats one of their main centres. Kerala alone has more than 40 species, almost all of them endemic to the southern Western Ghats.

The kurinji's name honours the Kunthi river of Silent Valley, where the plant grows in abundance. It is usually a shrub of 30–60 cm, though in sheltered places it can grow to two metres or more. Its flowers are bell-shaped and pale blue to violet, darkening with age, and they grow in dense spikes at the ends of the branches.

What makes the kurinji famous is its timing. Botanists call such plants plietesials: they grow vegetatively for many years, then flower gregariously (all together), set seed and die. The pattern is also known as mast seeding. Many Strobilanthes species do this, each on its own clock, ranging from a few years to about sixteen. For S. kunthiana, the clock is about twelve years.

The records are remarkable. Mass blooms of the kurinji in the southern hills have been documented in 1838, and at twelve-year intervals since: 1850, 1862, 1874, and so on through 1970, 1982, 1994, 2006 and 2018. Not every population keeps the same schedule. Different hills, and even different slopes, can be out of step by a few years, and scattered plants sometimes flower between the great blooms; but each population, once established, tends to hold its own rhythm.

Why wait twelve years?

How thousands of plants across a mountainside know when to flower together is still not fully understood. Some researchers have suggested that temperature fluctuations, possibly linked to climate cycles such as El Niño, help to set or confirm the timing; others think the rhythm is largely internal, set when a generation of seedlings germinates together after a bloom. No mechanism has yet been proven.

The advantages of the strategy are clearer, and they are shared by other mast-seeding plants such as bamboos. A plant that flowers rarely but all at once produces far more seed than seed-eating animals can consume, so that enough survive to replace the generation. A mass bloom is also more attractive to pollinators: during a kurinji year, honeybees work the slopes in huge numbers, and beekeepers in the hills prize the rare kurinji honey (kurinjithen). Rodents, insects and birds also feast on the seed crop.

The strategy has risks. A whole population lives and dies on the same schedule, so a fire, a landslide, an unseasonal storm or a construction project in a bloom year can wipe out a generation at once. After flowering, the dead stems form a dry mass of fuel that makes fire more likely, and fire in the following dry season can destroy the seeds lying in the soil. Heavy rain falling on slopes covered with dying plants can also increase soil erosion.

A flower in the culture of the hills

The kurinji is woven into the culture of southern India. In classical Sangam Tamil poetry, composed some two thousand years ago, the world is divided into five landscapes (tinai), and the landscape of the mountains is named kurinji after this flower; it is the landscape of love and of union, and its deity is Murugan. The Kurinji Andavar temple at Kodaikanal, dedicated to Murugan, preserves kurinji plants in its grounds.

For the Paliyan people of the hills of Tamil Nadu, the kurinji has served as a calendar: a person's age can be counted in the number of kurinji blooms they have seen. The Nilgiris, the "blue mountains", are often said to take their name from the colour the flower gives the hills. (Read about the hill communities of Munnar in The First People of the Hills.)

Where it grows: Munnar and the high ranges

Neelakurinji is a plant of the shola-grassland landscape of the southern Western Ghats: the rolling montane grasslands and the small dark forests in their folds (see A Changing Sky for how this landscape formed). It grows on the open slopes and especially along the edges of the sholas, where it finds both light and shelter.

The 2024 IUCN assessment recorded 34 subpopulations across 14 ecoregions: 33 in the Western Ghats and one in the Eastern Ghats, at Yercaud in the Shevaroy hills. The largest number are in the Nilgiris, followed by the Munnar hills, the Palani hills around Kodaikanal and the Anamalai. Around Munnar, the best-known blooming areas are:

• Eravikulam National Park, especially the Rajamala slopes, where visitors can see the bloom within the tourist zone;
• Kurinjimala Sanctuary, near Kottakamboor and Vattavada, on the eastern side of the high ranges;
• the slopes around Kolukkumalai, Top Station and Mattupetty, and parts of the tea estates where kurinji survives in uncleared patches.

In October 2006, during that year's great bloom, Kerala's Forest Minister Benoy Viswam announced the Kurinjimala Sanctuary, about 32 km² of grassland and shola in the Kottakamboor and Vattavada villages of Devikulam taluk. It was created specifically to protect the kurinji and its habitat, and it links up with Eravikulam, Anamudi Shola and Pampadum Shola national parks and Chinnar Wildlife Sanctuary to form a continuous block of protected high country. Lands held under valid private title were excluded from it, and its boundaries have been the subject of long disputes.

The kurinji's sisters

Neelakurinji is only the most famous of many Strobilanthes in the Western Ghats, and blooms reported in the news are not always of this species. Some examples of different rhythms:

Each of these has its own pollinators, seed predators and history. Researchers believe several Western Ghats Strobilanthes may already be extinct, and many more are known from only a handful of sites.

Other flowers of the high ranges

The kurinji's hills are among the richest places for wild flowers in India, and many grow nowhere else. A few of the groups a careful walker may see around Munnar:

• Balsams (Impatiens), jewel-like flowers of wet rocks and stream banks, flowering mainly in the monsoon. The Western Ghats are a global centre for the genus, and new species are still being found: two critically endangered balsams, Impatiens panduranganii and I. mankulamensis, were described from the Eravikulam and Mankulam forests in 2017.
• Orchids, including ground orchids of the grasslands and tiny epiphytes on shola trees, many of them endemic to the southern hills.
• The Nilgiri rhododendron (Rhododendron arboreum subsp. nilagiricum), whose crimson blossoms brighten the grassland slopes and shola edges in the dry season, a southern cousin of the rhododendrons of the Himalayas.
• Small treasures of the wet grasslands and rocks: bladderworts (Utricularia), carnivorous plants with tiny purple and yellow flowers; pipeworts (Eriocaulon); Exacum gentians; and the pink Sonerila of mossy banks.

Many of these plants flower in the monsoon, when the hills are wettest and fewest visitors come. For a botanist, the high ranges in July and August are as remarkable as any kurinji year.

2018: a bloom in the floods

The 2018 bloom in the Munnar hills was planned for as a major event: the state spent about ₹2 crore preparing, and officials expected more than eight lakh visitors (the 2006 bloom had drawn about five lakh). Then, in August, Kerala suffered its worst floods since 1924. Roads and bridges to Munnar were destroyed, tourists were barred from Idukki district for nearly two weeks, and repeated heavy rain delayed the flowering until after mid-September and rotted the flowers in many places. With about ten days of the season left, only about one lakh visitors had come. The best displays were at Rajamala and Kolukkumalai.

For the plants, an extreme monsoon in a bloom year is a test. A flowering generation depends on pollinators flying, on seeds ripening and on seeds settling into the soil before the dry season. Floods, landslides and prolonged rain at the wrong time can reduce all three. Scientists at the Kerala Forest Research Institute, led by K. A. Sreejith, began mapping the kurinji's distribution after 2018, partly to understand how climate change and natural disasters affect its life cycle; firm conclusions will take many more years.

Threats to the blue

Lost grasslands

The single greatest threat to the kurinji is the loss of its home. Over the last century and a half, the southern hills' grasslands and sholas have been cleared for tea, converted to plantations of eucalyptus, pine and wattle, and broken up by roads, farms, towns and resorts. In the Nilgiris, restoration ecologists estimate that only about 10% of the original shola grassland survives. The IUCN assessment estimated that the kurinji has lost about 40% of its habitat, and listed tea and softwood plantations, urbanisation, invasive species and climate change as the main drivers.

Invasive plants

Roads and plantations carry invasive plants into the grasslands. Wattle (Acacia), originally planted for fuel and tannin, spreads aggressively and shades out low shrubs like the kurinji. Others, such as gorse (Ulex), Scotch broom, Eupatorium and bracken, have taken over large areas of grassland in the southern hills; bracken has spread into areas once occupied by kurinji.

Fire and land disputes

Fire is a natural part of grassland life, but frequent, deliberate fires are not. In 2019, fires burned for about a week across parts of the Kurinjimala Sanctuary and neighbouring areas, including Pazhathottam, Kadavari and Chenduvara, with an initial Forest Department estimate of more than 1,000 hectares affected. Forest officials alleged that the fires were set deliberately to weaken the case for keeping disputed land within the sanctuary; local representatives disputed this, blaming a heat wave and a failure to cut fire lines in time. Whatever their cause, such fires kill kurinji plants and destroy seed banks, and in the years after a bloom, when dead stems lie thick on the ground, the risk is greatest.

The boundaries of the sanctuary have been contested since its creation, with competing claims from settlers, landholders and those with eucalyptus plantations inside it. Kerala's government has stated that the area of the sanctuary will not be reduced, while settlers with valid land documents will not be evicted. Resolving these claims fairly, and protecting the land that remains, is central to the kurinji's future.

Tourism

The kurinji's fame is a mixed blessing. Bloom years bring lakhs of visitors, and with them crowding on fragile slopes, trampling, people picking flowers and uprooting plants, plastic waste and pressure for new roads and resorts. Well-managed viewing, as at Rajamala in Eravikulam, with timed tickets, fixed paths and limited numbers, shows that people can enjoy the bloom without destroying it.

A warming climate

Climate change adds pressure on top of all this. The kurinji lives on sky islands, cool mountaintops separated by warm valleys, and many of its populations are already near the highest ground available. As the climate warms, the zone of suitable conditions moves upwards, and there is little further up to go. Changes in frost, a key force shaping the grasslands, could favour invasive trees such as wattle over native grassland plants. More intense monsoon rain and longer, hotter dry seasons raise the risks of landslides in the wet season and fires in the dry.

A more subtle question is whether a changing climate could disrupt the timing of the bloom, or of the bees and other pollinators on which it depends. Because the mechanism behind the twelve-year cycle is not understood, no one can yet say. What is clear is that a species which reproduces only once every twelve years has very few chances to adapt: each generation is a single roll of the dice.

Seeing the kurinji responsibly

• Go with permits and on official paths. In bloom years, Eravikulam and other sites run timed visits; book in advance and keep to the trail.
• Don't pick, uproot or carry away flowers, plants or seeds. Each plant is part of a generation that took twelve years to grow, and doing so is a criminal offence (see below).
• Carry out all plastic and waste, and never light fires in the grasslands.
• Visit in other seasons too, to see the balsams, orchids and rhododendrons of the high ranges, and support guides and businesses that care for the hills.

The kurinji measures time in twelves. Since 1838 its blooms have been recorded at the same steady pace. Whether there will be a bloom in 2030, and in 2042, and in the years after, depends less on the plant than on what the people around it do with the hills in between.

Note on sources: species counts for Strobilanthes vary between sources because the genus is still being studied, and blooms reported in the news are sometimes of related species. Bloom years given here are those recorded for the main S. kunthiana populations; local populations may flower in other years. Blooms around Munnar are expected next around 2030, but exact timing varies; check with the Kerala Forest Department before planning a trip.