What Can Your Houseplants Do For You? By Elaine Lockey

Golden pothos cuttings growing roots in water

Your houseplants do more than just look pretty on a window sill; they actively remove harmful air pollutants from the air of your house or office. In a controlled test by NASA, some were found to remove as much as 87 percent of indoor air pollutants in a 24 hour period.

You might wonder why NASA is interested in houseplants. Houseplants are studied for their effectiveness in keeping the air cleaner inside space stations. During long space flights or time in closed capsules, air pollutants build up creating hazardous conditions for astronauts. NASA, in a joint partnership with ALCA (Associated Landscaping Contractors of America), tested to see which houseplants perform the cleanup task better.

There are three main known contaminants in spacecrafts other than carbon dioxide: formaldehyde, benzene, and trichloroethylene. These contaminants are also the most common ones in our homes and offices as they are emitted by furniture, carpeting, fabrics, office equipment and other common materials. Benzene is also a product of tobacco smoke. Newer, more energy efficient homes have higher levels of indoor pollutants due to being more air-tight while older drafty homes may not have as much of an issue. The more air leaking in and out means a higher turnover of bad air to good air - a trade-off to be sure. The phenomenon of “sick-building syndrome” has grown with the construction of new buildings. Symptoms include itchy eyes, drowsiness, respiratory and sinus congestion, headaches and many more. Over the long term these can translate to asthma and certain cancers.

Some houseplants are better at cleaning a particular pollutant over another and some are better overall than others. In a very simple explanation, plants breakdown pollutants via photosynthesis, similar to how they convert carbon dioxide to oxygen. Their soil also absorbs harmful particles and renders them into harmless matter. To get the most effectiveness, NASA recommends 1 potted plant for 100 square feet. In an average 1800 square foot home, use 15 to 18 6-8” diameter plants ideally put into most rooms. Many of these plants are able to thrive in lower light conditions making them ideal for many homes.

“To test if our friendly green goo-gobblers provide a natural way of helping combat pollutants, researchers set up conditions as follows: They placed each plant type in a sealed plexiglass chamber and injected chemicals. After 24 hours, spider plants removed 96% of the carbon monoxide, and golden pothos removed 75%. They found plants with large leaf surface areas were the most effective in removing pollutants.” (University of Illinois Extension)

Photo courtesy of Parks Wholesale Plants

According to NASA, the best plants for removing formaldehyde were heart leaf philodendron (Philodendron scandens oxycardium), spider plant (Chlorophytum elatum), and golden pothos (Scindapsus aureus). Benzene was removed effectively by the flowering plants in the study - Gerbera daisy (Gerbera jamesonii) and chrysanthemum (Chrysanthemum morifolium).

Is it possible to have too many houseplants? According to my husband the answer is yes. However, he was thrilled to learn how they make our home cleaner - a great reminder I can give him next time I return with my newest purchase.

A complete list of plants that NASA tested, including the plants that removed each contaminant, by CSU Extension Agent Laura Pottorff.