Best Houseplants to Improve Indoor Air Quality
By: Julie Day
Golden Pothos (Epipiremnum aureum)
We all remember learning in science class that plants “breathe” by taking in carbon dioxide and releasing oxygen, which is why forests are so important in maintaining the delicate balance of the earth’s atmosphere. But did you know that certain tropical houseplants can also remove and process other, more harmful, chemicals from the air inside your home?
Dracaena deremensis ‘Warneckii’
Toxic Chemicals in Household Air
Homes and office buildings today are often more polluted than the outdoors. Modern buildings are tightly sealed and insulated to make them energy efficient, and they’re also full of synthetic materials that emit harmful gases and chemicals into the air. The result is a sealed bubble of unclean air that can lead to what is known as “Sick Building Syndrome.” Some of the most common indoor pollutants are:
- Formaldehyde: Commonly used in a number of items including particle board, pressed wood, foam insulation, cleaning products, and treated paper or fabric. If your home or office contains particle-board furniture, grocery bags, tissues, paper towels, or anything that has been treated to make it stiffer, wrinkle-resist, fire retardant, or water-repellent, then you’re likely to have formaldehyde in the air.
- Benzene: A solvent used in manufacturing paints, inks, plastics, rubber, dyes, pharmaceuticals, and detergents.
- Trichloroethane: Can be found in adhesives, varnishes, paints, and used in dry-cleaning.
At the very least, chemicals like these can irritate the eyes and skin, lead to allergic reactions, and cause headaches. At worst, they’ve been linked to more serious problems including asthma, cancer, anemia, organ damage, and birth defects. Given the pervasive presence of these chemical in our homes, it can be difficult to create an environment that is free of them.
Ficus tree (Ficus benjamina)
Research by NASA and ALCA
In the late 1980s, a two-year research study was conducted by NASA and the Associated Landscape Contractors of America (ALCA) to investigate ways to create healthy, breathable environments in outer space. They found that certain tropical plants, commonly used as houseplants, were quite effective in removing formaldehyde, benzene, and trichloroethane from the air and replacing it with breathable oxygen.
All plants provide some benefit to air quality, but their research showed that tropical plants (grown as houseplants in cooler climates) are particularly effective at processing gases and chemicals. Because they grow in dense rainforests with very little light, they have evolved to be very efficient at photosynthesis, which includes the absorption of gases from the air. In addition, as plants transpire (emit water from the leaves), air is drawn down around the roots, where root microbes quickly adapt and begin “eating” the harmful chemicals that are absorbed.
The result was a list of recommended plants for reducing toxic chemicals in indoor environments. Most are common houseplants that you should be able to find at your local garden center. Two of the recommended plants (Gerbera Daisy and Pot Mum) are ornamental blooming plants that are frequently brought indoors for seasonal decorations.
Heartleaf Philodendron (Philodendron scandens ‘Oxycardium’)
Top Plants for Reducing Indoor Air Pollution
- Bamboo Palm (Chamaedorea seifrizii)
- Chinese Evergreen (Aglaonema modestum)
- Dracaena (Dracaena sp.). Especially Red-Edged Dracaena (Dracaena marginata), Janet Craig (Dracaena deremensis ‘Janet Craig’), Warneckii (Dracaena deremensis ‘Warneckii’), and Corn Plant (Dracaena fragrans ‘massangeana’)
- English Ivy (Hedera helix)
- Ficus, or Weeping Fig (Ficus benjamina)
- Gerbera Daisy (Gerbera jamesonii)
- Golden Pothos (Epipiremnum aureum)
- Peace Lily (Spathiphyllum sp.)
- Philodendron (Philodendron sp), particularly Heartleaf (Philodendron scandens ‘oxycardium’), Selloum (Philodendron selloum), and Elephant Ear Philodendron (Philodendron domesticum)
- Pot Mum (Chrysanthemum morifolium)
- Snake Plant, or Mother-In-Law’s Tongue (Sansevieria trifasciata ‘Laurentii’)
- Spider Plant (Chlorophytum comosum)
For best results, have at least one six-inch plant for every 100 square feet.
Peace Lily (Spathiphyllum sp.)
Other Benefits of Indoor Plants
Of course a home or office building cannot exactly mimic the controlled conditions of a research lab, but it is clear that having plenty of healthy houseplants leads to a healthier home. In addition to processing carbon dioxide and harmful chemicals, houseplants improve indoor air quality by:
- Helping to maintain humidity levels: Dry indoor air is blamed for a host of respiratory problems, particularly in the winter, and plants emit water vapor during transpiration.
- Producing negative ions: Plant leaves produce negative ions, similar to many air purifying machines. Negative ions attach themselves to (and effectively remove) particles such as dust, mold spores, bacteria, and allergens. The presence of negative ions is credited for increasing psychological health, productivity, and overall well-being.
A variegated form of English Ivy (Hedera helix)
The Other Side of the Debate
Some researchers, including the EPA Indoor Air Division, remain unconvinced that houseplants are the answer to cleaning indoor air. The reasons for their doubt include:
- Houseplants should not be your only defense against indoor air pollution. Instead, pollution should be eliminated at its source by reducing the amount of synthetic material in your home or office, and by making sure buildings are well ventilated.
- The average home or office building is different from a controlled research lab, so it’s difficult to determine if the results translate to the real world, or how many plants are needed to get the same effect. While no one disagrees that plants process chemicals in the air, their exact rates and effectiveness are hard to prove outside the lab setting. Some critics believe it might take hundreds of houseplants to get the same results as the NASA/ALCA study.
- Too many plants can raise humidity levels too high, which could lead to mold and bacteria growth throughout the building. Indoor humidity levels should stay between 35%-65% to avoid turning your home into a “greenhouse.”
- Moist soil breeds bacteria, mold, and mildew. Don’t overwater your plants, and help control mold by “mulching” your houseplants with a one-inch layer of fine gravel or other porous material.
Corn Plant (Dracaena fragrans ‘Massangeana’)
- Clean the Air in Your Home with House Plants (article)
- A Guide to Indoor Air Quality (EPA)
- How to Grow Fresh Air (book by Dr. B.C. Wolverton)