Picking the right greenery can help rid the air of toxins
As I write this, the barometer is plummeting, rain is power-washing the windows, and a dog is hogging the wood stove behind me. Nobody is going outdoors in this tempest. The scene inside is every bit as cosy (and twee) as I've described it. At least it looks so on the surface. Yet floating around in the air are various compounds that are not good for me, the dog or the environment. The synthetic materials in my computer and office furniture are quite possibly emitting formaldehyde, xylene, toluene, benzene and various other not-so-healthy volatile organic compounds. And, although we're breathing normally, the dog and I may well be emitting some of the above, as well as ammonia, acetone and alcohol (and neither of us has been drinking).
Before you start thinking that this article should be in a different part of the magazine, let me introduce some plants. For a start, let's try areca palm (Dypsis lutescens) and moth orchid (Phalaenopsis). Both are sitting less than a metre away, and - here's where they fit in with the earlier rigmarole - they are helping to clear the air.
Plants, as we all know, take in carbon dioxide and give off water vapour and oxygen. However, they don't confine their gaseous diet to carbon dioxide alone: they are capable of breathing in other compounds, such as indoor pollutants, and rendering them harmless. When the leaves exhale water, air is pulled in to fill the vacuum, and it travels down through the leaves and stems into the root zone of the plant. There, the toxins are converted into nutrition by beneficial microbes, and by the plant's own mechanisms. You could say, the plant is eating the toxins.
Leafy, tropical plants are among the most voracious eaters of pollutants, because they have the highest rates of photosynthesis and transpiration. The light levels of their natural habitat, under the forest canopy, are not unlike those in our comparatively dim homes and offices, so they make perfect house plants. The fact that they transpire so much (that is, breathe out lots of water vapour) is an added bonus, as they can help to raise the humidity in a dry, centrally-heated room.
Dry air, as anyone who works in a hermetically-sealed office knows, can dry out the nasal membranes, causing irritation and a raised susceptibility to allergens and viruses. When the environment is more humid, plants transpire less, so they do not generally add to the moisture content in a room. House plants help maintain indoor humidity at between 40 and 60 per cent.
Some of the first research into the effect of plants on indoor air quality was carried out by Dr BC Wolverton of Nasa. He wanted to find a way of purifying the air in space stations, where the many synthetics emitted hundreds of volatile organic compounds (more than 300 were found in Skylab 3 in 1973). His work then, and after he left Nasa, used readily-available house plants, such as peace lily (Spathiphyllum), rubber plant (Ficus elastica) and Boston fern (Nephrolepis exaltata 'Bostoniensis').
The areca palm, which is fine, frondy and Victorian-looking, is one of the very best plants for processing pollutants. In its native Madagascar the areca can reach nine metres in height, but keeping it in a pot in an Irish home is likely to limit it to two or three metres. Because it splays out at the top like a green fountain, it is a perfect house plant: its slender lower parts take up practically no room, and the leaves arch into a graceful and sculptural canopy when it is raised on a table or plinth. It is also one of the best plants for adding moisture to the air: a good-sized specimen can transpire a litre of water over 24 hours. This means, of course, that it must be watered every few days.
Don't be tempted to follow the lazy man's method of leaving it standing in a saucer of water. This is a sure way of causing fungal root rot, one of the few disorders to which this elegant palm is prone.
My moth orchid, which shares a table with the areca (and various gangly pelargoniums), is also recommended for pollutant-removal. Tropical orchids, epiphytic bromeliads and some succulents exchange oxygen and carbon dioxide after nightfall (unlike most plants, which do this only during the day), so they are good choices for bedrooms, or in offices where the midnight oil is burned.
All plants, however, will benefit the indoor atmosphere. And there's lots of research into their other benefits: plants in an office reduce the numbers of sick days (as workers have fewer infections), promote better performance, absorb noise, filter dust and dirt from the air, elevate the general mood and reduce stress levels.
Many of us spend 90 percent of our lives indoors, where pollution levels can be 10 times higher than outdoors. Bringing the outdoors indoors is one way of making us a little healthier. Another is simply to get out into the garden - a place to which this column will very soon return.
Air freshners
• The top 10 for offices for the home, according to Dr BC Wolverton, are Areca palm (Dypsis lutescens), Lady palm (Rhapis excelsa), Bamboo palm (Chamaedorea seifrizii), Rubber plant (Ficus elastica), Dracaena (Dracaena deremensis 'Janet Craig' is the one recommended, but there are many similar kinds), Ivy (Hedera helix), Dwarf date palm (Phoenix roebelenii), Ficus Alii (Ficus binnendijkii 'Alii'), Boston fern (Nephrolepis exaltata 'Bostoniensis') and Peace lily (Spathiphyllum)