Following cyclone Nilam, botanist M. Udayakumar did a quick count of trees that contributed to branch falls on the long route from his house in Thiruninravur to Pachaiyappa’s College, where he works on an Inspire Fellowship project. “ Albizia saman — commonly known as rain tree and thoongu moonji maram — won the contest hands down. I was not surprised,” says Udayakumar who names it among trees that can’t be counted on to “stand their ground” in a cyclone.
“An import from tropical America, the rain tree has low wood density and the roots don’t run deep,” he explains. He brands a few other common trees as unreliable in a cyclone, notably Delonix regia (commonly called red gulmohar and sengondrai) and Enterolobium cyclocarpum (common names: earpod wattle and annai maram).
“These trees are preferred for their growth, but they are not native to India. Delonix regia comes from Madagascar and Enterolobium cyclocarpum is again introduced from Africa. They are made for a different environment and are incapable of withstanding challenges that lie outside of it. In the evergreen rain forests, nutrients are available in the top layer and the trees don’t have to probe deeper for them. Trees brought in from there can’t be expected to have a strong root system — they come with a particular bio-makeup and adaptation to the new environment is seldom complete,” says Udayakumar. “Moreover, most of these trees last just around 25 years.”
He makes out a case for native trees that have better wood density and root system and last significantly longer. “ Pongamia pinnata (ponga maram or pongam tree) has a wood density of 0.8 cm cube and lives for 50 to 60 years. Tamarindus indica (tamarind tree or puliyamaram) has a highly impressive wood density — 1.03 cm cube. The Tamil saying pudichallum puliyamkomba piditcharu — refers to the unusual strength of the tamarind tree. A tamarind tree can live for over a hundred years. Terminalia arjuna (Arjuna tree or maruda maram) has a wood density somewhere between 0.8 cm cube to 0.9 cm cube, and lives for more than 60 years. Azadiractha indica (vepamaram or neem tree) has a wood density of 0.8 cm cube to 0.85 cm cube and lives for over 50 years. In addition, all the parts of the neem tree have great medicinal value. Around 10,000 papers have been written to highlight this fact,” says Udayakumar.
Besides a propensity to plant good-looking, big-growing alien species, Udayakumar lists the practice of nailing trees as a significant cause of tree falls in Chennai. “Nailing sets in motion an insidious process of decay. By the look of it, the tree will be healthy — it will however be dying inside. Nailing opens up spaces for pathogenic micro-organisms, such as bacteria and fungi.”