Merge outdoors and indoors
In 1980 scientists at the John C. Stennis Space Center in the USA found that plants can purify air. B. C. Wolverton and his team measured the effects of various houseplants on the presence of volatile organic chemicals (VOCs) including formaldehyde, benzene, trichloroethylene and xylene.
It turned out that a number of plants are pretty good at absorbing VOCs, translocating the chemicals to their roots and breaking them down. A worthy deed, since formaldehyde and/or numerous other VOCs are a natural byproduct of many of the ingredients of modern life: plywood, particleboard, carpeting, synthetic fabrics and plastics, to name the most common. High on on Wolverton's good-plant list were the areca palm, lady palm, rubber plant, English ivy, Boston fern, Peace Lily. The spider plant, which has often been linked with air-purifying properties, wasn't quite as efficient.
Wolverton found that one of the factors influencing VOC-removal rate has to do with the rate of transpiration--that is, how much water evaporates from a plant's leaves. As the plant absorbs water through its roots, air is pulled into the root zone, where microorganisms facilitate the breaking down of the chemicals into sources of food and energy.
Still, the best of the air-cleaning plants can remove 1,000 to 1,800 micrograms of VOC per hour, the studies show, but that equates to less than two milligrams of bad stuff. Can people actually tell the difference? A Norwegian study found that office workers whose spaces had plants reported 23 percent fewer complaints of fatigue, stuffy noses, coughing and eye irritation than workers who had no plants nearby. No doubt helping alleviate discomfort was the fact that plants also increase the humidity level of a room to a more comfortable 30 to 60 percent.
Science has also been busy measuring some intangibles. Another study showed that workers are better able to solve problems and think of new ideas when plants are around. And yet another study found that people who performed a stressful computer task had 12 percent quicker response times and lower systolic blood pressure when plants were around. In fact, in some cases plants don't have to be immediately present; hospital patients recover a little faster from surgery and require less pain medication with just a view of a garden.
But that's another story. There are plenty of studies showing that people often report feeling less stressed when there are only pictures of plants or nature around. What tangible things do plants do when they're present? Studies have shown that people feel more attentive, think a little more clearly and possibly even more innovatively, when plants are around. They report feeling less stressed.
Researchers seem to be finding out that plants not only help remove airborne chemicals and dust, but they may help us feel generally better. Are we making too much of what plants can do?
Great Green Air Cleaners
Areca palm (Chrysalidocarpus lutescens)
Lady palm (Rhapis excelsa)
Bamboo palm (Chamaedorea seifrizii)
Rubber plant (Ficus elastica)
Dracaena 'Janet Craig' (Dracaena deremensis 'Janet Craig')
Pygmy date palm (Phoenix roebelenii)
Fig 'Alii' (Ficus macleilandii 'Alii')
Boston fern (Nephrolepis exaltata)
Peace lily (Spathiphyllum sp.)
Corn plant (Dracaena fragrans)
Golden pothos (Epipremnum aureum)
Florist mum (Chrysanthemum morifolium)
Gerbera daisy (Gerbera jamesonii)
Note: Some plants - such as dieffenbachia, some philodendrons and dracaenas, and peace lily - can be toxic to dogs; depending on the variety of plant and the size and weight of the dog, effects can range from mild oral irritation to poisoning. If you have a dog that likes to nibble, place these plants out of reach.
This great little book describes the care and culture of 50 plants that can help purify the air in your home or office, rating the plants on how well they remove chemical vapours, how easy they are to care for, etc.: How to Grow Fresh Air by B. C. Wolverton.