Heroic Houseplants

Can a lowly spider plant or pothos provide better air quality in your home or office?

by Christina Dennis — March 26, 2007

In one of the stranger science experiments undertaken by a curious teenager, Ryan Kim, the son of an allergy researcher in California, placed dog feces and moldy bread in containers around his house and measured how many nasty particulates were released into the air. The young Kim then introduced an English ivy plant into the containers to see what would happen.

After repeating the experiment, he discovered that the plant reduced airborne particles of fecal matter by an average of more than 94 percent over 12 hours. The level of mold in the air went down by 78.5 percent. The findings were impressive enough to be presented by his father, Dr. Kenneth Kim, at the November 2005 meeting of the American College of Allergy, Asthma, and Immunology in Anaheim, CA.

This does not mean, however, that you should rush out and fill your rooms with English ivy. For one thing, the plant is toxic and shouldn’t be placed near small children or pets. For another, the soil that feeds the plants sends out its own potentially dangerous microbes and waste products. But it is one powerful demonstration of the air-cleansing abilities of plants, a subject that’s been studied since 1986, when a NASA scientist, Bill Wolverton, tested houseplants for their detox potential in lunar space stations.

Though his “laboratories” were sealed chambers that can’t really mimic a home environment, Wolverton did come up with some intriguing findings: gerbera daisies, for one, removed benzene from the air. Golden pothos and philodendrons, both common houseplants, reduced airborne formaldehyde; and potted mums and peace lilies sucked up a noxious substance known as trichloroethylene. Wolverton’s research stimulated further studies, including a 1994 German report that proved one spider plant could, in six hours, detoxify a 100-cubic-foot room polluted with formaldehyde.

Soon after 9/11, when a New York City public school sought to improve air quality by importing 1,000 plants donated by a Florida nursery association, Wolverton revealed to The New York Times his optimum system for clearing indoor air. He recommends plants grouped in a planter that draws air through a filter of activated carbon and clay, a complicated system for the home gardener but one that’s currently in development by a Japanese company, the Actree Corporation.

Other experts, though, recommend one six-inch plant per 100 square feet of indoor area, or about 15 to 18 houseplants in six- to eight-inch containers scattered around an 1,800-square-foot house. What’s the best greenery for clearing the air? Happily, they turn out to be low-maintenance plants like parlor palms, philodendrons, peace lilies, spider plants, dragon trees (dracanae), pothos, and the weeping fig (ficus trees). Some studies have suggested that houseplants can reduce fatigue, coughs, sore throats, and other cold-related symptoms, and may help lower blood pressure and improve concentration.

That’s a big job for a lowly spider plant, but if you treat it right, you also reap the benefits of a friendly living thing that asks for little more than water and light.

Christina Dennis is a Philadelphia-based writer on health and medicine.