Air-Purifying Houseplants and Other Myths
It’s an enticing idea, creating little biomes in our homes filled with crisp plant-purified air. Nurseries market it and plant blogs post articles titled, 20 Best Plants for Cleaning the Air.
It’s not true.
This myth originated in the 1980s when NASA scientist, Bill Wolverton, studied cleaning volatile organic compounds (VOCs) from the air in small hermetically sealed environments. His results were promising. In his 1989 report, he writes, “If man is to move into closed environments, on Earth or in space, he must take along nature’s life support system.”
Our homes are swimming in VOCs. They off-gas from drywall, plywood, detergents, dyes, glues, furniture, aerosol, printers, even toilet paper. Some of the more common VOCs, formaldehyde, benzene, and trichloroethylene have been linked to kidney, liver, and nervous system damage and cancer.
I read Wolverton’s report and put a snake plant by my bed, a rubber tree in the kitchen, and a peace lily in the bathroom. If these plants were going to help us colonize Mars I figured a few in my apartment would make short work of any VOCs.
I believed because I wanted to believe. But, Wolverton’s study, where these houseplant claims almost exclusively come from, is flawed, or rather not applicable to our homes. Our homes are not small hermetically sealed chambers. Air, people, and pets move through them. They are also filled with crap.
More recent research has found that to equal the air-cleaning capacity of changing the air over once per hour, the typical air-exchange rate in an office ventilation system, you would need at least 10 plants per square foot.
In other words, you are better off just opening some windows.
Plant myths are easy to come by and gardeners eat them up like kale salad. Every school science fair (and I have been to a lot of them) has at least one experiment testing whether plants grow better when they listen to classical music or heavy metal (fourth-graders across the country are convinced plants like Mozart more than Slayer).
Once I received an email through the local Master Gardener listserv. A member was gushing about the virtues of eating lemons. Her most outrageous claim, lemons can cure cancer. At the time, my dad was dying from a lifetime of smoking and throat cancer. No amount of lemons was going to help him.
The Secret Life of Plants is a 1979 plant-lovers favorite. The book aims to prove not only the sentience of plants but their ESP-like connection with their human caretakers. The researchers tested this by attaching modified polygraph electrodes to their plants. Then, while the researchers are out in the world experiencing fear, excitement, pain, and pleasure, they record their emotions and later see if they correlate with reactions in the plants. In one experiment, researcher Pierre Paul Sauvin takes a trip with his girlfriend to a lakeside cabin 80 miles away from his plant. The authors write, “[his plants] would react with very high peaks on the tone oscillator to the acute pleasure of sexual climax, going right off the top at the moment of orgasm.”
Ficus cleaning our homes, lemons curing cancer, philodendron enjoying Bach, orgasmic begonias. We still believe we have dominion over “every living thing that moveth upon the earth.”
Filling a Brooklyn apartment with sprawling ivy so that you can breathe easier is the other side of the same coin that deforests a jungle to grow cheap palm oil. These trees, this earth, is here to serve me.
Of course, we benefit from and rely on plants. But, the idea that they exist to serve takes sneaky forms with “plant people.”
I hold beliefs that could easily be called myths. I believe in a sort of plant sentience and that a 400-year-old oak has something to teach us as does a potted pothos. I believe science is limited and often gets it wrong. At first, the scientific community dismissed Suzanne Simard’s work showing how trees communicate and share resources, even among different species.
I worked on a farm where cow manure was stuffed into a cow horn and fermented underground for the winter. After, it was dug up and stirred into water. We dipped willow branches into this manure-water. Then, under the full moon, flicked the water over the garden. I believe it improved the health of the soil and plants. That farm also installed speakers so the vegetables could listen to heavy metal.
We can’t begin to understand the complexity of the soil underneath us, the fungi running through it, binding with the roots of firs and elders. The trunks that stretch up, in the case of redwoods, 300 feet, transporting water and sugars up and down. Or the leaves, exhaling oxygen and taking in carbon dioxide all to the rhythms of a star 93 million miles away. This has been happening for 700 million years. We would be better off looking at how we can connect to these ancient rhythms rather than asking what’s in it for us.
My snake plant, rubber tree, and peace lily are still alive (and many others that have shown up over the years). I wipe down their leaves with a damp cloth so they can freely photosynthesize. Each spring, like daffodils, fungus gnats emerge from the potted soil. I chase them around the house and squash them between my fingers and semi-gloss walls. When I go out of town, I find a plant babysitter.
I don’t ask what my houseplants are doing for me anymore, but I choose to believe they are doing something.