March, a month when temperatures rise, trees begin to grow new leaves and pollution begins to recede. The silk cotton puts out its flaming red, orange and yellow flowers, setting Delhi alight, bringing visual respite from the grey, smoggy winter. With school holidays on the horizon, travel itineraries are composed like bad poems inspired by teenage crushes. Perhaps Japan this year to see the cherry blossoms immortalised in anime or the Netherlands for their tulip displays in Keukenhof.
Wrapped up in the dream of cherry blossoms, most Delhiites miss out on a spectacular show in their own backyard: the blossoming of the Indian Beech. Every March and April, these indigenous trees bloom, white, pink and a little bit of lilac, carpeting the ground with their inflorescence. Every March, the sight brings comforting nostalgia transporting me home, if for just a moment.
My work as an urban ecologist in the world of building sustainable cities allows me insight into what is planted, where and why. Pongamia pinnata is an urban planner’s favourite. Although it was recently moved into a different genus, Millettia, I continue to refer to it as Pongamia, sidestepping the complexities of botanical nomenclature.
With a broad-spreading canopy, short leaf-shedding season, delicately showy flowers, nearly evergreen leaves, and little to no maintenance required, Pongam trees are preferred avenue and median plants in several cities. The Pongam is a common sight in villages, too, as well as in research plantations exploring the tree’s biofuel potential.
My love for the tree began before I was born.
In her own way, my mother has always championed urban biodiversity. Thirty-odd years ago, she planted two Pongam saplings in front of our little white-and-red house in Hyderabad, a symbolic gesture representing her love for green as well as an unplanned carbon offset for the two kids she eventually conceived. One taller, the other broader, they became sentinels marking our house. Within a few months, I was born; three-and-a-half-years later, my brother followed.
“Pong-uh-mia,” I pronounced it for decades, until 2005, when I was corrected in botany class, “Pon-gam-ia”. Part of the Fabaceae family, the family of plants from which you get your vegetarian protein, I learnt that Pongamia pinnata is a powerhouse. It is not only a popular feedstock for biodiesel, an indigenous medicine, lactagogue (inducing milk production) fodder, a soil binder, but also an ornamental tree and a windbreak. Its utility spans spectrums and geographies. Pongamia pinnata, my botany textbook told me, was drought-tolerant, being perfectly adapted to intense sunlight and heat with its marvel of a root system. Conversely, it’s also a freshwater flooded forest species, with the ability to survive submergence for prolonged periods. Later, when I wandered Goa’s estuaries, I discovered it was also a mangrove associate, found on the fringes of mangrove ecosystems, being able to survive a wide range of salinities despite not having evolved any particular traits (physical or physiological) to do so.
With the global community calling for restoration of ecosystems, and the UN declaring 2021-30 the decade of ecosystem restoration, the Pongam has a lot to give. The tree’s potential (I like to to think of it as “powers”) to produce biofuel, withstand drought-like or flooding conditions, stabilise and enrich the nitrogen content of the soil has gained it quite the following across countries, India included. In Indonesia, Pongamia is being explored as an ecosystem engineer, to restore ecosystem services on degraded peatland and offer support to local agrarian economies. Studies have estimated that the tree is able to sequester 13.43 tons of carbon per hectares and fix nitrogen throughout its life. It also coppices well. These properties make it an excellent candidate for agro-forestry interventions on marginal lands. For these reasons, researchers in Bangladesh are proposing the tree be used in small-scale rural industries, while in Australia, research trials are exploring the tree’s use in phytocapping, or growing plants over the waste in landfills.
The oil from the seeds, known as karanja or poonga oil, has uses in ethnobotany—boiled with damar gum for pitching vessels, used as a liniment for skin and rheumatic disorders in the Ayurvedic and Siddha systems, in veterinary remedies, in soaps and in varnishes. The seed oil cake is used as an organic pesticide and fertilizer.
As the trees grew along with my brother and I, they rendered uncountable services to our family and neighbourhood, stretching into the space we called home. In the winters, my grandmother sat basking in the mosaic of sunlight formed by the leaves of the canopy, while in summers the vegetable seller would sneak a quick siesta beneath them. In the spring, cloud-tufted fledglings of Red-vented bulbuls, Tickell’s blue flycatchers and tailor birds made the leap of faith from their branches, learning to fly, while battles were fought between the butter yellow Allamada and powder lavender garlic creeper flowers to claim space on its branches. Pollinators waltzed elegantly as they sipped from the flowers, paying in pollen. My limited repertoire allowed me to identify these as purple sunbirds, honey and carpenter bees, and the common tiger butterfly.
In my attempt to expand that repertoire, I was led down the path of another discovery about the pollination mechanism of the tree, “keel explosion”. The arrangement of the Pongam’s flower petals are botanically termed papilionaceous or butterfly-like. Each five-petalled bisexual flower encloses its reproductive organs, the stamens (male parts) and the stigma (female part), within a pair of petals called the keel petals. These keel petals are enclosed by a pair of wing petals and hooked to a large, single standard petal that attracts pollinators.
When a pollinator of the right size approaches the flower, drawn in by the promise of nectar, it triggers the “explosion” that violently releases the reproductive organs from the keel petals. The stamens eject their pollen, which lands on the underside of the bees while the stigma collects accumulated pollen on the bee’s belly.
Skippers, blues and brush-footed butterflies, with endearing names like the Forget-me-not, Acute Sunbeam, Indian Sunbeam, Dark Cerulean, Common Cerulean, Pea blue, Common Banded Awl, White Banded Awl and Chestnut-streaked Sailer, although not pollinators for the Pongam, have their larval stage hosted by the tree. The Pongam also plays host to Kerria lacca, the commercially-important lac insect, which produces the resin that goes into shellac and a host of other products.
In 2006, my father passed away. My mother, brother and I would sleep in the same room at night, comforted by a tangerine yellow street light which filtered through the Pongam tree leaves into our open window. A nightlight, to keep at bay the nightmares that a death brought. Yellow light reflecting off green leaves, the trees watched us drowse, whispering lullabies as the wind played softly in the distance.
Since then, I have left the yellow safety of my home, and journeyed to places where I lived temporary lives, parts of the world where I met and fell in love with other trees. Ever faithful though, the two trees still stand, branches outstretched, anticipating my visits home, marking every year that my brother and I get older, carpeting the floor with their white, pink and lilac blossoms every March.
Rithika Fernandes is a Hyderabad-based urban ecologist at ICLEI South Asia, working with local governments on building sustainable cities