Over two years NASA scientists studied a dozen ornamental home and office plants to determine each plant’s air cleansing abilities. Not surprisingly, each individual plant genus had different success rates with pollutants. For instance, philodendron, spider plant and golden pothos removed the most formaldehyde molecules, while gerbera daisy and chrysanthemums were best at removing benzene. Dr. Bill Wolverton, formerly a senior research scientist at NASA’s John C. Stennis Space Center, Bay St. Louis, Miss., explained the phenomenon this way:
“Plants take substances out of the air through the tiny openings in their leaves, but research in our laboratories has determined that plant leaves, roots and soil bacteria are all important in removing trace levels of toxic vapors.”
In addition to counteracting off-gassing chemicals, plants improve indoor environmental quality by balancing humidity too. One plant will help purify air for about 10 square yards of living area, so the average living room might only need three or four to gain a benefit. In this case, more is probably better, but like all living things, plants need nurturing and care. As plants do accumulate dust, for the maximum environmental benefit, dust them to keep the pores in their leaves open for air intake and outflow.
Kamal Meattle explains exactly what to do in a fascinating “Ted Talk” presentation. He recommends the first three plants highlighted in red below. In the studies performed by researchers at an Indian University, these were the highest performers. Meattle claims they are the only plants needed to purify indoor air completely. In his presentation he gives exact numbers and heights of plants and in which rooms to place them. He is a fervent house and office plant advocate, and illustrates his point by rather dramatically stating man could live in a corked bottle with only these three plants to produce all the clean, breathable air we required. (Bookmark the Ted Talk page if you don’t have time right now, but do come back and listen. There are fascinating 15 minute talks on everything imaginable. I have yet to listen to a boring one.)
Areca palm: This is beautiful but takes a little more care than some people want to devote. It likes to be 5 to 8 feet from the window to receive filtered, indirect light. It hates the salts often used to soften water, so you may want to get a counter-top water purifier. It will need a little pruning, but make sure to prune only dead fronds as if you cut off brown tips, that will stop growth in that frond. The palm should also be put outside every three or four months to keep it healthy. It does become less attractive as it ages, but don’t we all?
Money Plant: In the Chinese culture the five-leaf money tree plant is said to bring good luck. As it is a very fine air cleaner, this seems to be less superstition than it would appear. Money trees like higher humidity than is generally found indoors, so placing the pot above a tray with water and pebbles will allow the water to evaporate around the plant. (Don’t let the pot sit in water, however!) In the growing season, the plant’s soil should be damp, but during winter when the plant is slightly dormant, you can let the soil dry out more between waterings. Don’t let its roots get soggy or leaves will start to drop off from over-watering. Pruning the plant on top will encourage a bushier, shorter plant. The leaves are critical to air cleansing and pruning encourages lots of them.
Mother-in-Law’s Tongue: This plant can be differentiated from the snakeskin plant by noting the yellow border as opposed to the snake’s yellow banded leaves. It is almost impossible to kill, as it tolerates light to dark and uneven watering behavior. Of course, never watering or always soaking it will do it in eventually, but it will still take time. This plant has a very nice upright architectural form with leaves that can grow to three or four feet. If you pot it in sandier soil and fertilize with a cacti formula only during the growing season, it will do extremely well.
Dwarf/Pygmy Palm: This tree is slow-growing, but it can reach 10 feet tall. It is exceptionally good at removing xylene. If you give it a little summer vacation outside, you may even get some small dates. If you live in a hot apartment it will need lots of water, however. Fertilize it during the growing season and it will always look its best. Oh, it hates to get chilled, so please don’t put it near an entryway where it might get a cold blast of air.
Boston fern: These ferns have always been one of my favorites as they are so fluffy and elegant. Boston ferns love high humidity, so if you don’t want to put the planter on top of pebbles in a water dish or mist it twice a week, keep it in the bathroom. Keep the soil damp or you will always be picking up little dropped leaves that have yellowed and fallen off. Oh, this plant cannot survive without water for your two-week vacation, so if you leave? Give it away or hire a plant-loving housesitter.
Dracaenas: There are about 40 varieties of dracaenas, but the one most familiar to people is called the “corn” plant. (Its appearance is reminiscent of how corn leaves form on a stalk.) NASA’s Clean Air Study showed dracaenas helped remove formaldehyde, making them one of the best plants to have in any home with off-gassing materials.
English ivy: Although this is a good formaldehyde, benzene, toluene, xylene and trichloroethylene remover, it is poisonous to both humans and pets. Certainly this can be a lovely plant for adults, but if you are introducing a puppy or toddler to your home it’s not worth the risk. Also, ivy doesn’t like acidic water, so if you harvest rainwater for indoor plant watering, you may have trouble with it. Go on vacation with this plant and it will probably be alive when you return. It can survive a bit of dryness but never wet feet.
Australian sword fern: If you live in the south, you do not want to let this plant outside, as it spreads like crazy there. Indoors it is one of the ferns that loves bright light and prefers a west-facing or bright east window. If your home is overly warm, don’t hang this fern from the ceiling or it will require much heavier watering. (Heat rises.) Anything up to 75°F and it will flourish as long as you water it a few times a week.
Peace Lily: These plants sprout an occasional lovely white lily if they are cared for year-round. They prefer medium to low light like that from a north window. Humidity needs to be addressed too, as if they start losing leaves they are not getting enough. They should be fertilized year-round, as they do not go dormant in the winter like many other plants.
Rubber Plant: If you have a problem with latex, this plant literally bleeds it and should be avoided! If not, it is a resilient specimen that can live in low light conditions and should be allowed to dry out between waterings. Why? Over-watering is the one sure way to kill it.
Weeping Fig: This is more commonly known as a ‘ficus’ with many hybrid varieties from which to choose. They need half a day of daylight and can be finicky if stressed or moved from one location to another. If they are near a wall they should be turned frequently for their inner foliage to stay full. A new plant might enjoy some earth worm castings, and you must remember to fertilize them. Watering weekly usually works, but if you let more than the top two inches of soil dry out, your ficus will not do very well and begin to drop its leaves.
Meattle recommends that houseplants be grown hydroponically, but this may be not practical for some residents. Most houseplants do enjoy an occasional pruning, being fed regularly and repotted before they become rootbound. Also it is important to carefully examine any houseplant for pests before you buy it. Incorporating a one-week quarantine into your routine will also pay big dividends. Spider mites and most other sorts of infestations will usually hatch out within five to ten days. If this happens, our advice is to bring the plant back to the store or toss it before you cause an epidemic.
If you want to find an inexpensive way to have exotic-looking plants year-round, it is very easy to force bulbs to bloom indoors in late winter and early spring. In October plant tulips, narcissus (daffodils), hyacinths, crocus, scillas, grape hyacinths, or lily of the valley in pots and keep them inside. (An internet search will give you information on how to care for each type of bulb.) As a matter of fact, the begonia at left was accidentally potted with a houseplant and bloomed indoors this month.
All kinds of herbs, like the basil and oregano seedlings pictured above, are quite easy to grow form seed indoors with proper feeding and watering. Of course, for the best indoor air quality and the most beautiful presentation, use a variety of plants and they will remove a variety of air pollutants.
Other articles of interest:
- How Compatible are Window Farms, Aquaponics and Apartments?
- The Urban Chicken Coop Movement
- Can Apartment Culture Embrace Urban Agriculture?