Clearing the air with indoor plants

G Magazine

It’s time to bring your green thumb indoors. With our homes and offices harbouring astounding levels of pollution, the humble pot plant will help you breathe easy once more.

Indoor plants

Indoor plants can improve air quality and your wellbeing by taking up carbon dioxide and replacing it with oxygen, as well as helping kick-start a process to remove other toxic gases from the room.

Credit: iStockphoto

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It's an all-too-common misconception that pollution is exclusively an outdoor problem. Are our indoor spaces really the safe haven from emission-spewing cars and industrial smokestacks that we think they are? The
scary truth is that levels of some pollutants are, in fact, highest indoors.

With most Australians spending 90 per cent of their time indoors, between offices and homes, indoor air pollution is bound to take its toll on our collective mental and physical health. The CSIRO estimates the cost of poor indoor air quality in Australia to be as high as $12 billion a year due to illness and decreased productivity.

One solution is neither high-tech nor expensive, and it comes straight back to nature. Indoor plants can
improve air quality and your wellbeing by taking up carbon dioxide and replacing it with oxygen, as well as helping kick-start a process to remove other toxic gases from the room.

Allergic to work?

"We've all had the experience indoors when we feel a little bit headachy, perhaps a little bit giddy, and if it gets worse than that, an irritation in your throat, eyes or nose... all these effects of indoor pollution are what's known as sick building syndrome," says Margaret Burchett from the Plant Environmental Quality Group, based at the University of Technology in Sydney.

Indoor air contaminants include volatile organic compounds (or VOCs), carbon dioxide, carbon monoxide, nitrogen oxides and fine particulates, to name just a few.

The high concentrations of pollutants indoors is "partly due to the air coming in from outside with all the pollution it contains, mixing with the [chemical toxins from] indoor materials," says Burchett. And while outdoor air pollution, including vehicle and industrial emissions, is regulated, there are no enforceable limits to indoor air contaminants.

Brand-new buildings can cause sick building syndrome because of all the new furniture, fittings and surface finishes. That 'new smell' from fresh wall paint, newly laid carpets and brand-new furniture might seem 'clean', but the chemicals behind the smell are toxic. Breathing these VOCs into your lungs can not only make
you feel unwell in the short-term but, over a longer period, may cause respiratory diseases and cancer.

People living or working in older buildings are also at risk because materials used to be made from more toxic substances than they are today, and while the VOC emissions gradually decrease over time, most synthetic materials will continue to emit low levels of pollutants for their entire life. Electrical items such as computers and TVs will emit VOCs whenever the plastic casing becomes warm.

While air-conditioners filter dust, mould spores and pollens from the air, they don't remove VOCs and other gases. And if they're not regularly cleaned and maintained, indoor air quality deteriorates further. Add carbon dioxide from everyone breathing in a crowded office, or at home from burning gas appliances such as cooktops, and you have a heady cocktail that could make you feel more than a little woozy.

Sucking it up

There are currently no national guidelines for safe levels of VOCs indoors. In 1993 Australia's National Health and Medical Research Council recommended 500 parts per billion (ppb) VOCs as a goal, but this has since been rescinded. Some people start to feel unwell when levels exceed 200 ppb, says Burchett. She and her team found that, in offices where the concentration of VOCs was close to 450 ppb, placing three or more plants in the room reduced the levels to 100 ppb.

Basic biology taught us all that the leaves of plants take in carbon dioxide and expel oxygen. But what's less commonly known is that often it's the soil - or more specifically, the bacteria in the soil - that does the hard work of removing toxins from the air. Soil microbes will jump into action when they notice toxins at levels as low as 50 ppb.

"The leaves aren't so much what take up large quantities of VOCs. They will, but comparatively more slowly than the micro-organisms in the soil. Both the leaves and soil microbes will also take up nitrogen oxides," says Burchett. However this doesn't mean you can just plonk a pot of soil on your desk to filter the air: "There's a symbiotic relationship with the plants and the microbes for the VOCs."

Making it work for you

If you have visions of vines swallowing up your telephone and pots covering every surface, think again. A surprisingly small amount of greenery makes a big difference. A British study of thousands of homes noted that, if a house had six or more pot plants, it had a third less nitrogen oxides in the air than houses without any indoor plants. The Green Building Council Australia acknowledges the inclusion of indoor plants in its Green Star ratings system and recommends a minimum of a 300 ml pot per two workstations.

The greater the surface area of the leaves on the plant, the more carbon dioxide it will be able to take out of the air. However, when it comes to lowering levels of VOCs, different types of plants are similarly effective because it's the normal bacteria in the potting mix that does most of the work.

Most importantly, choose plants that will work with the current light and space restrictions of your home or office. "There are a myriad of plants that are very good indoors," says Stuart Swaddling, managing director of TPR group, a national supplier for tropical plant rentals.

Swaddling recommends you look at how much light is available before you make your selection. "There are plants that will do very well in low light conditions; Janet Craig is one that can basically live in a cupboard. But any flowering plants need to be as close as possible to a window, so long as it's not direct sun."

"More plants are killed with over-watering, so the soil needs to be a good, viable mix that drains well. Buy good potting mix. If you get your soil out of the garden, it's not going to be any good. More often than not, it holds too much clay in it, which holds too much water for indoor plants," he says. "It's important, too, that air gets through to the soil and the roots, but recycled rubber tyre mulch or any [type of] pebbles will still let enough air through."

Swaddling brushes off claims that bringing plants into the home encourages dirt and bugs: "There's nothing in soil that isn't already in the house, in relation to moulds and muds, particularly if you're buying a soil mix from a local nursery or hardware it's not going to give you any problems."

"Think of plants as cushions for indoor decor; they really can make a difference to the look of your home," says Robert Prince, chief executive of the Nursery and Garden Industry Australia. "You can change your plant, or change the pot and it will suddenly look very different in your home."

And the best thing, according to Burchett, is that the plants will continue to regulate the air quality all by themselves: "[the level of air pollution] is not only reduced; it's reduced and it's maintained."

General maintenance

Most indoor plants need more water in summer than over winter. Re-pot into a bigger container every spring or if new leaves are coming out twisted, as this means the plant is root-bound (the roots are overgrown and tangled in the pot). Remove any dead or dying leaves from plant. This will keep them looking their best and make sure their growth isn’t inhibited. Mealy bugs, a common pest, can be controlled easily by applying an eco-oil regularly over a period of three or four weeks. And lastly, rotate your pot plants every few weeks to ensure they grow symmetrically.

Learn more about how to care for your indoor plants by signing up to the Plant/Life Balance Facebook page here.

G tip

The leaves of indoor plants can become dusty, which stop them from getting light. Spray foliage with a soft cloth every few weeks.

Easy indoor greenery

G's pick of low-maintenance plants to detox and spruce up your home and workplace.

Well-suited to dimly-lit bathrooms, ferns thrive in humidity and will gather quite a lot of their moisture from the air while you shower. Their umbrella-like leaves look great in space-saving hanging baskets.

Mother-in-law’s tongue
These semi-succulents have a tongue-twisting botanical name (Sanseveria trifasicata) and thin, sharp leaves. Tough as nails, they don’t need much water and are most commonly killed by overwatering.

Peace lily
These (Sathiphyllum sp.) plants like humid conditions out of direct sun. Wait until the leaves start to droop before giving them a good dose of water. Keep slightly closer to a window if you want flowers.

Dwarf date palm
Place this palm (Phoenix roebelenii) in a semi-sunny position and wait until the soil dries out before watering again.

Sculptural, slow-growing and hardy enough anywhere near a good light source, yukkas need a sandy soil that drains well. Go easy on the watering and make sure that the roots aren’t left sitting in water for long periods.

With striking flowers that can last for months and, in some cases, brightly coloured leaves, bromeliads grow well in warm well-ventilated offices but do need regular watering in the summer. The more light they get the longer the flower will last, but they can tolerate low levels of light.

Zanzibar gem
Gaining in popularity as a hardy indoor plant, Zamioculcas zamiifolia is renowned for being almost impossible to kill, highly pest-resistant and able to tolerate very little light and little water.

Janet Craig
Dracaena deremensis is one of the easiest indoor plants to look after. Growing quite large, it might be more suitable as a floor plant. It can survive in extremely low light providing it’s not overwatered.