One spring afternoon, my aunt noticed the potted ferns in my mother's living room were looking dehydrated. "But they're silk," said my mother in amazement. "How can silk plants be wilting?" Upon closer inspection, the plants did look a little droopy, and the misnomer became an inside family joke. "Don't forget to water the silk," my mother would say.
My parents incredible outdoor gardeners turned to silk after losing several houseplants to neglect. After the silk began to droop, my parents reverted to plastic plants a move toward convenience many families have made.
Yet according to Dr. B.C. Wolverton, an environmental consultant and retired NASA scientist, research indicates live plants are worth the extra trouble. In his book, How to Grow Fresh Air, he describes the way houseplants, when used strategically, filter toxins from the air inside your home.
"Our idea is to let plants be the lungs of a building, like the tropical rainforests are the lungs of the Earth," says Wolverton. His firm is developing greenhouse window boxes designed to pump filtered air into a room, and has designed indoor ecology gardens in Tokyo.
As most houseplants evolved under the damp canopy of the rainforest, they developed the ability to suppress air-born molds and microbes. While at NASA, Wolverton demonstrated that plants also break apart the chemicals most commonly released by plastics and synthetic household products.
Many volatile organic compounds (VOCs) in homes and schools have been linked to cancer, neurological disorders and sick building syndrome.
As high levels of synthetic chemicals can impact astronauts aboard space stations, Wolverton initially began investigating plants as potential air purifiers in microgravity environments. Scientist Gerard Heyenga currently works on a similar project at NASA's Ames Research Center. He recommends selecting houseplants that are robust and easy to maintain.
"Plants like ferns and ivy are good air filters," he says, "and they also show clear signs when they need to be watered."
As over-watering is one of the more common houseplant killers, Sarah Ostrenga, houseplant buyer at the San Francisco Bay Area's Yama Gami's, recommends the snake plant to new gardeners looking for a low-maintenance filter.
"If you buy something that looks pretty but is hard to maintain, you might be disappointed," she says.
Cheryle Yednak, a gardener in Santa Cruz, California, suggests the peace lily, a plant Wolverton says targets ethyl and methyl alcohol as well as acetone.
"The peace lily fits most houses well because it can grow in a dark corner, and, when exposed to bright, indirect light, it will bloom."
For those with a little gardening under their belts, Wolverton recommends plants from the palm and fern families. He found that the Boston fern targets formaldehyde a chemical used to preserve carpeting, upholstery fabrics and the foam in mattresses and couch stuffing. In contrast to the Boston fern, the lady palm removes less formaldehyde, but filters more ammonia than any other houseplant tested.
Wolverton says this specialization will make plants the indoor air technology of the future. He projects roof-top greenhouses will one day adorn apartment complexes, and that indoor gardens will become a staple of the green building industry.
His firm hopes to release a patented UV lamp planter in American markets later this year. The soil-free device uses pebbles, activated carbon and zeolite to wick water to the plant, and has shown to increase a plant's filtration capacity by nearly 100 times.
According to Wolverton, the pot makes use of the tiny microscopic organisms that live near the roots of all plants. Unlike manmade filters that absorb chemicals like a sponge, plants suck air into the ground when they transpire.
Microscopic organisms then break the chemicals into fundamental sources of energy and life. As each plant species evolved with different microbes, many plants filter one type of chemical better than another.
"Spider plants are also excellent," says Wolverton, "because they target benzene, the chemical released from house paint."
To diminish the levels of benzene, he recommends opening a window to increase air circulation, and then moving in several spider plants. For an average 12-by-12 room with standard levels of chemical toxins, two or three healthy plants will usually do the job.
Wolverton believes people see the best health results when they place plants in strategic breathing zones, like around their desk at work, where air is often re-circulated through dusty ventilation systems.
"Plants need to be placed where you spend the most time breathing," says Wolverton. "On the nightstand next to the bed, or perhaps on either side of your favorite chair."
The atmosphere in your home will certainly benefit from that added splash of green, at least according to a Washington State University study that found houseplants reduce stress and help people relax. Plants have also been associated with increased employee productivity and a patient's ability to tolerate pain and physical discomfort.
"This is why houseplants are so important," says Wolverton. "Not only do they target the invisible chemicals right under your nose, they also increase the overall quality of your life."