Gardeners' Dirt
November 02, 2012

by Beth Ellis, Victoria County Master Gardener

Edited by
Charla Borchers Leon, Victoria County Master Gardener
Photo by Beth Ellis/Victoria County Master Gardener
Spider plants do well in hanging or tall pots or on pedestals that encourage their cascading habit. Small plants from flowering stalks allow for easy propagation.
Sansevieria, also known as alligator plant and mother-in-law's tongue, are tough plants that require very little water. They are reportedly toxic to pets.
ABOVE LEFT:  Boston ferns do well in hanging pots or sitting on pedestals and prefer high humidity and bright light.
ABOVE RIGHT: The weeping fig, commonly known as ficus, prefers bright light, high humidity and often drops leaves when moved. Care in placement should be taken as it is reportedly toxic to pets.
ABOVE: Peace lily (Spathiphyllum sp.) - Foliage does well in low light.
Golden pothos does well in hanging pots or trained to supports. It propagates by stem cuttings in water and does well inside in most any kind of light. Care should be taken as it is reportedly toxic to both people and pets.
Do you ever walk into a building and within a few minutes begin to experience itchy, watery eyes, stuffy sinuses, headaches, dizziness or even nausea? If so, then you may be experiencing something called "Sick Building Syndrome."

Don't laugh - it's a real problem for a lot of people, and you may be one of them.

Sick Building Syndrome is caused by off-gassing of volatile organic compounds (VOCs) used in the production of building materials, furnishings and household products. It turns out that in our efforts to make our homes and offices more insulated and energy efficient, we've just traded one problem for another.

Those old leaky windows and drafty vents we've been so hasty to replace are actually a mixed blessing - even though they allow conditioned air to escape, so too do things like formaldehyde, benzene, toluene, xylene, trichloroethylene and a whole host of other nasty air-borne chemicals.

NASA's contribution

Ron Howard's riveting movie "Apollo 13" showed audiences everywhere the need for clean air in an enclosed environment. In the film, we are shown how the NASA astronauts of that harrowing flight cobbled together bits and pieces of their failing spacecraft to create a makeshift air scrubber that allowed them to survive. While it is fairly unlikely you and I will ever face imminent death because of the air quality of our homes, there is a real possibility that indoor pollutants could impact our long-term health.

And this is where NASA steps back into the picture. A study conducted by Dr. B.C. Wolverton and other NASA scientists in the 1980s revealed the value of houseplants in improving air quality of enclosed environments Results of the study can be found in Wolverton's book, "How to Grow Fresh Air: 50 Plants that Purify Your Home or Office." While the study was intended for space stations, the results are proving highly beneficial for people who spend most of their hours in tightly sealed, energy efficient-homes and offices.

A few of the best

NASA scientists determined that tropical plants are best for the task, because adaptation to low light conditions makes them most efficient in gathering light and airborne chemicals necessary for photosynthesis. Fifteen to 18 plants are recommended per 2,000 square feet. Plants should be in 6-inch or larger pots (the larger, the better). Below are a few selections from NASA's list.

Lady palm (Rhapis excelsa) - Lady palms prefer bright light, moist (not soggy) soil, good drainage, high humidity and average household temperatures. If frond tips turn brown, trim with pinking shears to disguise the cut. Propagate by division. Lady palms filter formaldehyde, xylene, toluene and ammonia. Reportedly non-toxic to pets.

Boston fern (Nephrolepis exaltata) - Boston ferns love high humidity, bright light, average home temperatures and consistently moist (not soggy) soil. Place in humid bathrooms or kitchens having bright light. Propagate by division. Boston ferns filter benzene, xylene and toluene. Reportedly non-toxic to pets.

Spider plant (Chlorophytum comosum) - Spider plants do best in hanging baskets where their cascading habit can be most appreciated. Provide bright light, low water and typical household temperatures. Flowering stalks result in baby plants, making propagation easy. Spider plants filter formaldehyde, xylene and toluene. Reportedly non-toxic to pets.

Weeping fig (Ficus benjamina) - Provide bright light and humidity and avoid drafts for best results. Let soil dry slightly between waterings. Ficus usually lose leaves when moved, but this is normal. They filter formaldehyde, xylene and toluene. Reportedly toxic to pets.

Golden pothos (Epipiremnum aureum) - Provide low to bright light and normal household temperatures. Allow soil to dry slightly between waterings. Propagate via stem cuttings in water. Trim for fullness. They are great in hanging baskets or trained to climb. Pothos filter benzene, formaldehyde, xylene, toluene and trichloroethylene. Reportedly toxic to pets and people.

Snake plant/alligator plant/mother-in-law's tongue (Sansevieria trifasciata) - The biggest danger these tough plants face is overwatering. Use well drained soil, water a couple of times a month in warm seasons and less in winter. Provide low to bright light, normal household temperatures, and avoid drafts. Propagate by division. Sansevieria filter benzene, formaldehyde, xylene, toluene and trichloroethylene. Reportedly toxic to pets.

Peace lily (Spathiphyllum sp.) - Foliage does well in low light, but encourage blooms by placing in bright light. Provide regular watering and moist (not soggy) well drained soil. Avoid drafts and maintain normal household temperatures. Peace lilies filter benzene, formaldehyde, toluene, xylene, trichloroethylene, as well as ammonia. Reportedly toxic to pets.

Breathe easier

The plants described above are just a few of many identified as good air cleaners in the NASA study. Consider getting a few, make sure to place those with potential toxicity out of reach of pets and children and begin to reap the benefits of clean air in your home and workplace.
Chemicals Filtered By Houseplants
Formaldehyde - Carcinogenic. Found in pressed wood products, insulation, adhesives, paper products (ex. facial tissues, roll towels), paint, polyurethane and more. Click here for more info.

Benzene - Carcinogenic. Found in crude oil, gasoline, and cigarette smoke. Used in production of plastics, resins, nylon and synthetic fibers, lubricants, rubbers, dyes, detergents, drugs, pesticides, and more. Click here for more info.

Toluene - Nervous system and organ damage. Found in gasoline, paints, nail polish, cosmetics, rubber cement, stain removers, fabric dyes, inks, adhesives, and more. Go here.

Xylene - Nervous system and organ damage. Found in motor and aviation fuels, solvents, perfumes, insect repellents, dyes, pharmaceuticals, insecticides, and others. Go here.

Trichloroethylene - Carcinogenic. Found in solvents for greases, oils, fats, waxes, and tars. Also in refrigerants, paint removers/strippers, adhesives, spot removers, rug-cleaning fluids, and more. Go here.

U.S. Department of Health and Human Services Household Products Database

Books :
Wolverton, B.C.
"1997 How to Grow Fresh Air: 50 Plants that Purify Your Home or Office," Penguin Books.

Websites :
Indoor Air Pollution FAQ
NASA info : List of air-filtering plants
Top Houseplants for Improving Indoor Air Quality
Sick Building Syndrome
Sick building syndrome symptoms
The Gardeners' Dirt is written by members of the Victoria County Master Gardener Association, an educational outreach of Texas AgriLife Extension - Victoria County. Mail your questions in care of the Advocate, P.O. Box 1518, Victoria, TX 77901; or, or comment on this column at