Climbers, not potted plants, are the right choice for green walls in Delhi

This monsoon, Delhi is at its verdant best. With the soot and dust washed off, leaves are finally flaunting their original shades. Even the naked patches of earth, turned sandy and gritty from the city’s construction debris, have burst into untamed greenery.

Somehow, many of the vertical gardens installed on concrete pillars supporting flyovers and elevated metro corridors in the past few months do not seem to share this happiness. Except for the ones flourishing in the VIP zones, thanks to the special attention they get from the civic authorities, or those replaced recently, vertical gardens in most other parts of Delhi look more like a collage of black plastic pots rather than blooming greens.

Perhaps, they are still too young or are recovering from the intense summer and vandalism at the hands of unruly citizens. Perhaps, the horticulturalists were wrong in selecting the right variety of plants. Perhaps, the pots they chose were not roomy enough for the roots to grow, and are already being replaced by larger mesh baskets. But clearly, the authorities are still struggling to get this experiment right.

The idea itself — draping concrete structures in greens — is excellent. Greenery along busy roads can cut air pollution caused by vehicular emissions. These natural layers trap dust, which can contribute 26% of the total summer pollution in Delhi according to a study by IIT-Kanpur. Moreover, since surfaces such as roads, pavements or rooftops absorb heat and set the temperatures soaring, plant covers can provide an effective sink to dispel heat-islanding.

The idea, however, is not new. Much before vertical gardens were planted into coco peat stocked in small pots, attached to modular racks and hung over concrete structures, most city gardeners used the humble, non-fussy climber plants for vertical greening.

A view of Vertical garden at ITO in New Delhi, India, on Saturday, September 8, 2018. (Sanchit Khanna/HT PHOTO)

Singapore, which pioneered this concept, started by covering concrete flyover columns with climber plants such as Ficus pumila and overhead bridges with flowering species such as bougainvillea. Along with other methods, the city-state still continues to use creepers for its ‘Skyrise Greening’.

Delhi residents have banked upon climbers to create drapes of green outside the windows and balconies to block out the harsh summer sun. Till not so long ago, the gates and archways were adorned with climbers. They were also used to cover fences and boundary walls for aesthetics and privacy.

The beautification drive before the Commonwealth Games in 2010 involved greening of flyovers and much of this was accomplished by growing climber plants. Even today, walls of elevated roads and metro corridors that are lined with creepers make for the best visual relief from the starkly geometric cityscape.

To function effectively, a green wall must be a carpet of green. “You can’t achieve this with a few leaves growing from a handful of potting soil, which these new vertical gardens essentially are,” says C R Babu, professor emeritus at Centre for Environment Management of Degraded Ecosystems at Delhi University.

Climbers are the best choice for vertical greening for multiple reasons. While most of the plants grown in vertical gardens flourish only in the shade, the right varieties of creepers would have no such requirement. They are low maintenance and do not demand frequent sprinkling of water. Over time, climbers form a dense cover with their large, hardy leaves that can fight Delhi’s dust and air pollution.

Climbers also create the micro-climate that sustains biodiversity. They attract butterflies and honeybees, which help in pollination. Their undergrowth supports earthworms, insects and a hundred micro-organisms. They flower in bounty.

So what are the climbers that can flourish in Delhi’s climate? Babu’s list is long: Vernonia grandiflora, Ficus scandens, Bignonia unguiculata, Thunbergia grandiflora, Thunbergia mysorensis, Ipomoea purpurea, Ipomoea coccinea, Ipomoea cairica, Ipomoea quamoclit, Jacquemontia, Jasminum officinale, Jasminum humile, Campsis radicans, Campsis grandiflora, Tinospora cordifolia, Coccinia grandis, Pyrostegia venusta and Cryptostegia grandiflora.

Like any naturally grown plant, climbers take their time to flourish and may not have an instant greening effect like a vertical garden would. They may also not grow uniformly or fit tamely into the patterned, designer green walls that the city authorities want to build for beautification.

But Delhi’s need for effective, low-maintenance green walls is more than a matter of vanity. So while vertical gardens may have their use in the short term, the planners will do well to plant hardy creepers alongside so that they can eventually replace those potted plants.

First Published: Sep 10, 2018 02:47 IST