Living green walls: India should look to vertical gardens to combat heat, pollution

Years before vertical gardening became a buzzword in urban spaces, I attended a symposium on landscape gardening conducted by the French Embassy in New Delhi. Since registration was open mainly to architects, I had to argue and coax my way into being accepted. I felt a little self-conscious about being the only one in the hall whose name tag read “gardener” under qualification, but it was an illuminating experience.

It was also when I was introduced to someone who would soon become one of my green heroes – botanist Patrick Blanc, credited with popularising vertical gardening. An unforgettable image showed him standing in front of a tropical garden turned on its side and soaring above him. With his wispy hair dyed a vivid green and clad in leafy camouflage printed pants, he presented a dreamlike image, as if he had stepped out of the canvas of fellow Frenchman, Henri Rousseau. The tropical jungle was located in the courtyard of a Paris Hotel and held the appeal of a lush arbour.

Since Patrick had studied how trees and shrubs grow naturally out of crevasses in cliffs in very little soil, he applied that knowledge in his design. His own home was like living in a rainforest and his work, shown at the Museums of Miami and Madrid, is path breaking. He uses hydroponics along with his own invention of drip irrigation – where roots are sandwiched behind felt sheeting designed by him, through which a judicious mix of plants is anchored. Only plants which have shallow roots are carefully selected. Water mixed with nutrients is pumped through the drip irrigation system at regular intervals, on the principle that plant roots need food, not soil.

There is nothing faddist or new-age about going green in vertical spaces – very real benefits accrue. Vertical gardens possess the magical ability to soften the harsh lines of cityscapes. As gardens disappear in cities and the skyline mutates into angular outlines of steel and glass, the views reflected off these towering edifices are harsh. Concrete jungles also create heat islands.

The green walls of vertical gardens are an antidote to urban alienation from nature. Psychological studies have confirmed the stress-busting effects of being surrounded by green leaves. Another most important aspect of increased vegetation is that it lowers temperatures. Green walls and roofs are great for thermal insulation. An even more significant benefit for Indian cities, is the reduction of pollution levels through photosynthesis. Depending on the placement of the green wall, both air and noise pollution levels can be dramatically lowered. Some plants, like chlorophytum (or spider-plant) prove more efficient than others at cleaning air and are also perfect for vertical gardens.

The water consumption for a vertical space is much less than for a horizontal garden. When a pump is installed, the run- off water can be reused to water the wall. For commercial spaces such as multi-storey office towers, indoor walls alive with plants, are a far better option than than art in the lobby – all that you need for healthy plants, are artificial lights and regular watering. Vertical gardens can be used to partition spaces, block off windows that look out at a less than desirable view and are far cheaper than creating a horizontal garden of similar size, despite the initial investment.

For private homes, verticagrowing creepers which adhere tightly to vertical surfaces, planted along a wall. These are rooted in the soil at the base of the wall and are a cheaper alternative to installing a system through which nutrients are fed to the plant from a vertical surface.

I have covered my boundary walls with ficus pumila, better known as chipkali bel or creeping fig. It does extremely well in shaded areas and its spread over the wall can be encouraged by smearing the wall’s surface with a thin mixture of farmyard manure or gobar khad (available at most nurseries) and lime. My boundary walls need little maintenance, apart from occasional pruning, and are home to a flock of small birds. Sunbirds, bulbuls and oriental white-eyes have all nested in the thick stems of the ficus pumila, and I am awakened every morning to the mellifluous notes of an avian orchestra.

At hill-stations, Boston Ivy and Virgina creeper make for very attractive wall facades. The wall itself does not suffer any damage with any of these three creepers, and this green cover can be encouraged to grow onto the walls of the main house with ease, although pruning will be a chore.

Pune has some of the best nurseries in India, conducting innovations in vertical gardening and tissue culture. Their efficient installations are perfect for commercial spaces and residential towers for group housing. For larger areas, drip systems fitted with timers to regulate the feeding of plants are installed.

For private homes up to a height of six feet and 50 sq feet in area, a drip system is not necessary. These vertical gardens can be watered with a hose. Plastic containers (approx 50 x 7cm in depth) can be filled with lightweight coco peat and a handful of soil, then fitted onto an aluminium grid frame work. This frame can be stand alone or attached to a wall’s surface (which has been water proofed). All plants with shallow roots that do not grow to a height of more than 2 feet can be planted in a vertical garden. Balcony walls in high rises can be transformed into herb or flower gardens depending on light, wind and humidity.

Some of the most fuss free plants suited to Indian cities for outdoor walls are widelia, verbena, portulaca, starlight and panda ficus, asparagus sprigii and merrii, all varieties of duranta and sedum. Succulents and cacti do well in arid zones like Delhi. A melange of variegated leaves in contrasting colours can be used to create a pleasing tapestry, as well as larger leaf varieties like philodendron and sheffleras. Indoor walls with restricted light should use the syngonium varieties, money plants of all colours, chlorophytums , aralias, roheos and cryptanthus.

Here are some instructions for a simple do-it-yourself vertical garden of 8 to 9 feet, so you can improve a dull corner of your home with some life, even with limited space.

Materials required: Bore-well perforated end pipe in high-density polyethylene, four inches in diameter. (Bore holes should be at least one inch in diameter. These come in lengths of about 21 feet, so one pipe will yield two columns when sawed in half.)

A plastic funnel to fit onto the top end of the pipe for neat watering and feeding.

Soil mix – coco peat, garden soil, neem khalli, farmyard manure and broken down charcoal pellets. All of these are available at nurseries, except charcoal, which should not be treated with any accelerant. (An ironing man should be able to give you some)

Seedlings – You can reserve one pipe for a portable installation of seasonal flowers. This flower tower will be easy to care for and vivid with petunias, sweet alyssum, variegated leaf and trailing nasturtium. Another section can be for green permanent plants. Ferns do well in coastal cities with high humidity. I have had to wrap the fern column in coconut fibre and place it next to my fish pond in Delhi for added humidity. It is ten years old.

Pack the pipe with soil mix, and then plant it a pit between 1-2 feet depending on how sheltered the location is. If space is restricted, it might be better to insert the seedlings through the holes before placing it upright. You can anchor the seedlings with a wad of moss or coconut fibre in low rainfall areas. Water with a hose and occasionally top up with a weak solution of NPK. For pests, mist with a suspension of neem oil and water.

Selina Sen’s book Gardening in Urban India was published this year by DK Random House.