In this era of growing emphasis on energy efficiency, many of us who live in temperate zones or colder are seeking ways to better seal our homes to achieve higher efficiency in heating and cooling. But that effort has a downside as well.
he more well-sealed a home is, the higher will be the concentration of substances in the inside air that can affect your health.Paint, furniture, dry-cleaned clothing, aerosol sprays, and building materials emit formaldehyde, benzene, and other gaseous substances.And, hopefully to a lesser degree these days, there is smoke from cigarettes, cigars, and pipes.There are also irritating particles suspended in the air, such as dust, pollen, and animal dander.Add to that the fact that average Americans spend almost 90% of their time indoors.Associated health problems range from headaches to respiratory diseases to cancer.
Phytoremediation to the Rescue
Phytoremediation is the practice of using plants as air purifiers.Our focus here will be on plants in the home as opposed to outdoor plants that may also be used to rid the air and soil of pollutants.(For information on the use of trees for phytoremediation, please see "Phytoremediation:Popular Poplars.)
Building on NASA's experiments with air-purifying plants in space, a number of recent studies offer convincing evidence that certain house plants are capable of removing an impressive amount of pollution from indoor air.Researchers at the University of Technology in Sydney, Australia, found that small clusters of Dracaena deremensis ‘Janet Craig' and Spathiphyllum 'Sweet Chico' (Peace Lily) placed in an office setting, where the air contained high concentrations of volatile contaminants, reduced that pollution by 75%.Even more encouraging is the fact that the reduced levels were sustained over the entire 12-week period of the study.
Researchers at Washington State University in Pullman, Washington, worked with a number of pollution-reducing plants to see if they might also reduce particulate matter in the air.Although not as impressive as the Australian study, the plants removed 20% of particulate contamination in an office setting.More research needs to be done to determine which plants and in what number are the most effective in removing "dust."
How do plants do it?
All plants absorb some gaseous pollution through tiny pores, called stomata, in their leaves. The photo magnification at the beginning of this article shows what stomata on the leaf surface look like. The green spots are stomata, and the inset is a close-up of a single stomate. Some plants are able to absorb more than others.Particulate matter that comes into contact with the potting soil is removed by the microorganisms living in it.In both cases, plants break down the polluting substances into harmless components.
Which plants are the best?
Testing continues with various house plants to determine which ones, besides the two already mentioned, are the best contaminant removers.University of Georgia, Athens, researchers have identified five plants that are "super-removers":Hemigraphisalternata (Purple Waffle Plant), Hedera helix (English Ivy), Asparagus densiflorus (Asparagus Fern), Tradescantia pallida (Purple Heart Plant), and Hoya carnosa 'Tricolor' (Variegated Wax Plant).They are pictured in the chart below.
Researchers are also working on producing microorganisms optimized to metabolize pollutants that land on the soil in pots.These can then simply be added to the potting mix for more effective pollutant removal.
The current recommendation regarding the number of plants needed to remove contaminants effectively is six or more plants from the chart below for every 1,200 square feet or so.I just did a quick check of our house plants and discovered that we have almost every variety on the chart.
Truth be told, the check actually wasn't so quick.I counted pots as I went along and discovered that we have 135 potted house plants!I can certainly breathe easier now, though, knowing that many of those plants are busy 24/7, removing contaminants from the air in which I spend the better part of my day and all night.
Some retailers are anticipating brisk sales of air-purifying plants as is wholesaler, Costa Farms. Among retailers selling plants with tags promoting their air-cleaning abilities are Lowe's and Home Depot.
Thank you to DG members AngelSong, jode, tashmoore, jnana, sandpiper, monochromatico, and gabro14 for the contributions to PlantFiles used in this article.
About Larry Rettig
An enthusiastic gardener for over 50 years, my first plant was a potted Ponderosa Lemon tree ordered from a comic book ad at age 15. I still have it, and itís still bearing lemons! My wife and I garden on 3/4 of an acre, both flowers and vegetables. Although our garden is private, it's listed with the Smithsonian Institution in its Archives of American Gardens and is on the National Register of Historic Places. We garden organically and no-till. Our vegetable garden contains a seed bank of vegetables brought to this country from Germany in the mid-1800s. For more info: http://davesgarden.com/community/blogs/m/LarryR/. Photos that appear in my articles without credit are my own.