Exotic vs native conundrum: What to plant in Bengaluru?

It is that time of the year when Bengaluru starts receiving rains, and tree-planting activities will start within a month. Known as Garden City, the city becomes colourful in summer with exotic flowers, while the various parts of the city also continue to lose huge native trees for infrastructure projects.

Many experts do not like Bengaluru’s fascination with exotic species, such as Tabeubia and Jacaranda. “The trees commonly known as blossoms of Bengaluru are all species imported from elsewhere,” points out N M Ganesh Babu, an associate professor at Transdisciplinary University, a Bengaluru-based private university.

“They have been planting wrong non-native species for the last 50 years. Now it is the peak of the trend,” he says.

“When the British came here, the city looked parched with dry lands here and there. They thought they would add some colour to the city, that’s how initial exotic varieties such as Tabeubia came to Bengaluru,” explains Ganesan R, a botanist at Ashoka Trust for Research in Ecology and the Environment (ATREE).

Ganesh Babu points out that the BBMP has been planting Conocarpus lancifolius, an exotic flowering plant and a mangrove species native to the coasts of America, Brazil, and Mexico.

“In the Yelahanka region, I saw so many saplings of Conacorpus. I took up the issue with the Bruhat Bengaluru Mahanagara Palike (BBMP). They say it has been chosen due to its high survival rate,” says Babu.

“This cannot be done at the cost of human and animal health. Researchers from Gujarat and other states have studied it and say it causes colds, coughs, asthma and allergies among humans. Knowingly planting this amounts to spoiling the ecosystem of Bengaluru,” he says.

“There is no doubt it’s a hardy plant and can grow in dry regions, but it has its health impacts. For the same reason, Jacaranda is not planted anymore,” says Sridhar Punathi, former principal chief conservator of forests at the Karnataka state forest department.

“These desert plants do not fetch rain; after four years, they will look awkward with no prominent flowering. Planting this should be stopped immediately,” says Babu.

The Gujarat government banned the planting of Conacorpus trees in January 2024. The reason cited was “the adverse impacts on the environment and human health”.

“We think the exotic varieties adapt to the city, and animals and birds also adapt to them. There was a study to prove that local animals adapt to these exotic trees. But we don’t look beyond this. We don’t know if the trees really get adapted to the city,” Ganesan says.

“From a biodiversity point of view, we are trying to force-fit the local animals into the trees. Due to monoculture, these plants may not be genetically diverse. Seeds are not available everywhere. They do not have mother trees, and seeds need not have good genetic quality as they do not get their native pollinators and dispersers,” he adds.

The golden trumpet Tabebuia tree in full bloom flowers at the campus of Vidhana Soudha in Bengaluru on Saturday.

Zonal plans for tree planting

Ganesan says that the city administration does not consider what to plant where. He proposes a plan that details the type of plants to be planted in various areas.

“Commercial areas and layouts cannot get the same plants. A fig tree cannot go to a commercial area because it will grow huge. Narrow spaces should have smaller trees. In layouts and human habitations, we should plant trees with flowers and fruits that people can use. Culturally important trees should be planted around temples. At present, there is no such plan or understanding with the BBMP,” he explains.

“We blame the trees when they get uprooted during rains,” he says, adding that proper planning can avoid this.

Ganesan has served on the BBMP’s Tree Committee in the past. He says the BBMP should plan tree-planting zones and species to ensure that they are “not seen as villains by the residents and citizens.”

43 native plants

Bengaluru is considered a transitional zone. The state forest department has made a list of plants for cities in transitional zones, which does not cover most of the native species that are native to the city.

“Bengaluru is 3,000 sqft above sea level, which can allow many species, including those in the Western Ghats, to grow there,” says Babu.

In fact, in August 2023, Lalbagh Botanical Gardens toyed with this idea and planted various species from the Western Ghats inside the garden.

“Bengaluru is conducive to planting, with the right temperature, rainfall, water availability, moisture, and climate. Everything we plant should grow,” says Sridhar Punathi. He points out that the survival percentage can be as high as 80.

Ganesh Babu heads EcoSpace foundation, an NGO promoted by Trans-Disciplinary University based in Yelahanka. The foundation has identified 143 species native to Bengaluru, which can be planted in apt locations as they can survive the city environs better. The list of trees shared with DH for this article. will soon be published officially

Saplings are planted at the same location every time, maybe because they do not survive,” observes D T Devare, a trustee of Bangalore Environmental Trust. He says BBMP should target a high survival rate rather than a high plantation rate.

According to Devare, the use of proper tree guards is one factor that can improve survival. “Iron tree guards help saplings survive better, and they don’t get stolen if properly placed on the ground,” he says.

“Instead of 1 lakh bamboo guards, plant 60,000 trees with iron guards. The survival rate would be the same,” he adds.

BBMP started planting saplings near lakes as there was no more space on the roads. Devare explains that in the past, forest officials in BBMP have been approached with proposals to make space for trees on roadsides. The higher officials agree to do it, but the lower rung refuses, citing tender conditions and other issues, and the buck gets passed on. On some pavements, the forest department has been able to plant trees, which he feels should be done across the city.

‘Pay for the survived plants’

“It’s important to have a result-oriented or survival-based payment system for tenders. The payment may be higher, but you will be paying only for the trees that survived,” says Sridhar Punathi.

The forest department’s tree planting guidelines mention a gap of 10 metres between the trees. Sridhar Puanthi says high-density tree planting can be done with a two-metre gap wherever space is available, such as roadsides, parks, lake beds, etc.

This was experimented with in 2019 on the Agara lake bed near HSR Layout. He says the plantation has been doing well without much need for water.

Punathi now heads Bamboo Society of India, a pan-India nongovernmental organisation that promotes bamboo.

He proposes that bamboo be planted in some areas. Bamboo is a fast-growing plant with high carbon sequestration potential, multiple uses, and monetary value. “It absorbs 30-40% more carbon and releases 30% more oxygen than average trees,” he says.