It is hard not to be alarmed at the apocalyptic pollution in Delhi – according to several monitoring agencies, the air in the national capital is the worst it has been in 17 years. People exposed to the air, particularly during peak smog hours, are reported to be suffering from hacking coughs, a burning sensation in the eyes and throat. Schools have been shut, visibility on roads is dangerously low.

These are but the short-term effects. With every lungful of breath, toxic gases and particulate matter enter the bloodstream, raising the risk of heart-related diseases and cancer. The gas chamber has sent Delhi’s residents scrambling for solutions. While the sale of electric air purifiers and anti-pollution face masks has gone up considerably over the past month, there has also been an increase in the purchase of natural air-purifying plants from nurseries across the city – a cheaper alternative for many.

Filling homes, gardens and balconies with plants and trees seems like an obvious step to combat the smog. Apart from giving oxygen, certain types of plants are also adept at filtering out specific types of toxins from the air.

NASA to the rescue

Research funded by the US space agency, National Aeronautics and Space Administration, in the 1970s tried to find a cost-effective solution to improving air quality on board long-term space missions. It was discovered that enclosed capsules aboard the International Space Station were susceptible to filling up with gases like carbon monoxide, formaldehyde, benzene and toluene. These are the most common air pollutants, also found in Delhi's air:

Benzene: Found in plastics, pesticides, cigarette smoke, cleaning products, lubricants, and synthetic fibres.

Trichloroethylene: Found in spot removers, adhesives, rug-cleaning solution, correction fluid, and paint removers.

Formaldehyde: Found commonly in carpets, glue, paint, upholstery, building materials, cigarette smoke, fuel-burning appliances.

Carbon Monoxide: Gas stoves, ovens, water heaters, vehicles, generators are some major sources.

NASA found that the most feasible way to address this problem was to grow certain varieties of plants that were able to remove toxins from an enclosed testing chamber.

A list of 50 plants was compiled by NASA. Listed below are the ones easiest to maintain and most commonly found in nurseries around Delhi.

Lady Palm (Rhapis excelsa)

Broadleaf Lady Palm. Credit: Wikimedia Commons
Broadleaf Lady Palm. Credit: Wikimedia Commons

This durable palm species adapts well to living indoors and is among some of the easiest palms to maintain. It grows slowly, which makes it ideal as an indoor potted plant, but can grow taller than 14 feet in height when allowed to grow freely in soil. Water generously on alternate days, making sure that the soil is well drained.

Spider plant (Chlorophytum comosum)

Spider Plant. Credit: Wikimedia Commons
Spider Plant. Credit: Wikimedia Commons

Also known as air plants, spider plants grow quickly and look great in hanging baskets. They need water two to three times a week, and are among the easiest houseplants to grow – making them a great choice for beginners or forgetful owners. In bright, indirect sunlight, spider plants send out shoots with flowers that eventually grow into baby spider plants or "spiderettes". The leaves grow quickly and help to absorb harmful substances like mould and other allergens, so it is perfect for those with common dust allergies. It also helps to absorb small traces of formaldehyde and carbon monoxide.

Bamboo palm (Chamaedorea seifrizii)

Chamaedorea. Credit: Wikimedia Commons
Chamaedorea. Credit: Wikimedia Commons

Also called the “reed palm”, this palm prefers bright indirect light. New plants will lose of some of their inner leaves as they adjust to indoor settings. This plant likes to stay uniformly moist, but does not like to be over-watered or to sit in standing water.

Rubber Plant (Ficus robusta)

Rubber Plant. Credit: Wikimedia Commons
Rubber Plant. Credit: Wikimedia Commons

Rubber plants grow well indoors, preferring moderate light. Young plants may need to be supported by a stick, but the stem thickens with age, and the plant can reach up to a height of 8 feet. Wear gloves when pruning a rubber plant, as the milky sap may irritate the skin. Water thoroughly when young, then allow the soil to become fairly dry before watering again. In winter, keep rubber plants slightly moist. This houseplant releases more oxygen than most other plants, and purifies indoor air by removing chemicals such as formaldehyde.

Boston Fern (Nephrolepis exaltata “Bostoniensis”)

Boston fern. Credit: Wikimedia Commons
Boston fern. Credit: Wikimedia Commons

The Boston fern grows up to 4 inches in height with a spread of up to 5 inches. It has feathery ferns, which are best displayed in hanging planters. This fern prefers bright indirect sunlight. Keep the soil barely moist, and mist frequently with warm water. Said to act as a natural air humidifier, the Boston Fern removes formaldehyde and is a general air purifier.

Dragon Plant (Dracaena marginata)

Dragon tree. Credit: Wikimedia Commons
Dragon tree. Credit: Wikimedia Commons

This is an attractive, stiff-leaved plant with colourful foliage, that is sometimes known by the name dragon tree. It thrives in loose, well-drained soil and warm climates. The dragon tree likes indirect sunlight, and need to be watered sparingly. It eliminates formaldehyde, xylene, toluene, benzene, and trichloroethylene.

Golden pothos (Epipremnum aureum)

Epipremnum aureum. Credit: Wikimedia Commons
Epipremnum aureum. Credit: Wikimedia Commons

Also known as Devil’s Ivy, the money plant flourishes in a variety of conditions, and can grow up to 8 feet long. It is also considered one of the most effective indoor air purifiers for removing common toxins. Though it is commonly grown indoors in a container filled with water, it can also be potted in soil with a moss stick to provide support to the vines. It needs to be watered sparingly and can be trimmed when the tendrils get too long. Devil's Ivy eliminates formaldehyde, xylene, toluene, benzene, carbon monoxide.

Aloe Vera (Aloe barbadensis)

Aloe vera. Credit: Wikimedia Commons
Aloe vera. Credit: Wikimedia Commons

Aloe Vera is primarily known for its gel, which is excellent for healing burns and cuts. It is easy to grow in indoor sunlight, and needs to be watered only once a week. Aloe helps to keep your home free from benzene, which is commonly found in paint and certain chemical cleaners. When new shoots appear through the soil, they can be removed and repotted to yield additional plants.

Ficus/Weeping Fig (Ficus benjamina)

Weeping Fig. Credit: Wikimedia Commons
Weeping Fig. Credit: Wikimedia Commons

A hardy houseplant that can grow between 2 and 10 feet in height, it needs bright, indirect light, and dry soil between waterings. Although it has air-cleaning abilities, it does not respond well to the cold or stress. Refrain from moving it around too much, as it will go into shock and shed all its leaves. Ficus plants eliminate benzene, formaldehyde, and trichloroethylene.

Peace Lily (Spathiphyllum “Mauna Loa”)

Peace Lily. Credit: Wikimedia Commons
Peace Lily. Credit: Wikimedia Commons

This is a compact plant which grows to up to a height of 3 feet. Peace lilies are hardy and tolerate neglect. They prefers indirect sunlight and high humidity, but need to be placed out of drafts. For best results, the Peace Lily should be thoroughly watered, then allowed to go moderately dry between waterings. The leaves should be misted frequently with warm water (note: the pollen of lilies is toxic for pets).

Snake Plant/Mother In Law’s Tongue (Sansevieria Trifasciata)

Snake plant. Credit: Wikimedia Commons
Snake plant. Credit: Wikimedia Commons

Grown for its striking, upright sword-like leaves, the snake plant is easy to grow and spread once baby plants appear. Avoid overwatering and it will flourish even in low lighting conditions. This plant eliminates benzene, formaldehyde, trichloroethylene, xylene and toluene.

When purchasing plants, instead of buying pre-potted ones, it is advisable to ask for saplings in bags, which are cheaper and can be transplanted in various combinations for a fuller pot. In particular, palms, spider plants, snake plants and aloe do well together.

Conversely, pre-potted plants that have thick growth and a number of shoots can be separated, so the individual plants can be repotted.