Gerbera Daisy (Gerbera jamesonii) - Best Air Cleaning Plant #5

One thing you may have noticed is that our list of air cleaning houseplants is that none of them so far have been flowering plants. Sure, plants like the Mass Cane are capable to producing flowers, but as houseplants they rarely ever do.

Which brings us to #5 on the list-gerbera daisies.

Gerbera daisies are a bit of a misnomer, as they're not really daisies, but in the sunflower family (Asteraceae). You can tell by the sturdy stems, thick leaves, and the shapes of the petals on the flowers. Gerbera daisies are native to southern Africa, and come in all kinds of beautiful colors. Its natural states are yellow, red, and orange, but growers have managed to produce pink, white, salmon, cream, and crimson flowers. In some cases, the same flower can even have petals of different colors. It's a perennial plant, meaning that if you grow it outdoors (in a frost-free climate) it'll wilt and look dead over the winter but pop back up in the spring.

The gerbera daisy (also called "gerber daisies" or "African daisies")--and in fact the entire genus--was named in 1737 by Dutchman Jan Fredric Gronovius in honor of an 18th century German medical doctor, naturalist, and botanist named Traugott Gerber. Gerber worked as a medical doctor in Russia and also took medical expeditions around the work searching for medicinal plants and herbs. Funny thing is, no one knows exactly why Gronovius decided to name the genus after him, but with over 30 species in the wild and over 100 species in total, the name stuck.

For years I worked at 1-800-Flowers, and that's where I first found out that Gerbera daisies are a popular cut flower (in fact, they're the fifth most popular cut flower behind roses, carnations, mums, and tulips). Here's one of their more popular arrangements:

As pretty as these flowers are, I always felt it kind of a waste that someone would pay upwards of $70 for two dozen of these, and they'd just die after a few weeks.

The cool thing about Gerberas, though, i that they make a good houseplant as well. In other words, not only will the flowers last for weeks, if the plant is well cared for, it'll bloom indoors in the autumn and winter.

I was excited to order my first-ever Gerbera daisy houseplant, again from 1-800-Flowers.

It's a bit pricier, but I've never, ever had a problem with plants from 1-800-Flowers, and buying from cheap places like K-mart always end up costing me more (saving $5 on a bag of potting soil has ended up costing me $50 and counting in fungus gnat remediation).

This is what I got in the mail.

Yes, a little disappointing that there are only two flowers and not nearly as many leaves as in the photo, but hopefully with some TLC more flowers and leaves will be growing. The plant is in excellent health, with no dead leaves, vibrant flowers, strong stems, and NO FUNGUS GNATS.

I also absolutely love the ladybug planter, which comes with a plastic insert for you to transplant the plant in from the small container it comes in.

Overall, it's not a bad little gift to give to someone. As for me, I'm going to transplant it in a bigger pot hoping for a lot of flowers and growth. 

Like the English Ivy, the gerbera daisy gets one of the highest ratings for removal of chemical vapors from Dr. Wolverton. 

Some care tips: 

1) Temperature: Keep between 60-65 degrees Fahrenheit in the daytime and 45-50 degrees at night. 

2) Sunlight: It likes full sunlight to semi-sun, but you need to protect it from the sun at midday to prevent the blooms from aging too quickly.

3) Care and feeding: Keep soil evenly moist but not soggy. Feed regularly during the growing season. Keep on a cool windowsill in the autumn and winter months. 

Update: A few weeks after repotting the daisy, the two flowers started drooping. Thanks to sites like the National Gardening Association's, I realized I was not alone and that this was a fairly common problem. Here are some tips I found:

1) Keeping the leaves healthy is more important than the flowers--if the flowers wilt, just cut them off. As long as you continue to keep the leaves fed, sturdy, and green, new flowers that are more acclimated to your environment will take their place. 

2) Temperature is important. Gerbera daisies like it cooler than most plants, so find that perfect spot in the house where they get good sunlight in the morning but are otherwise shady and cool.

Dumb Cane (Dieffenbachia camilla): Best Air Cleaning Plant #18

There are actually two plants by go by the name of "Dumb Cane", the Dieffenbachia "Exotica Compacta" and the Dieffenbachia camilla. The differences have to do with the variegation. Both have broad, green leaves, but Exotica Compacta seems to have a more "splotchy" look to the whiteness in the middle of the leaf, while Camilla (pictured here) has a more solid white pattern.

In either case, they have similar air cleaning qualities and both are stunningly beautiful houseplants.

The reason it's called "dumb cane" is interesting. Their sap contains calcium oxalate. You might recall this also occurs in Golden Pothos; as with that plant, if you bite into any part of the plant it can cause your throat to swell and you can lose your speech for several days. This is why you want to keep these plants far from children and pets.

You'll want to keep these plants in bright, filtered light; if the setting is too dark the leaves can lose their variegation. It's another plant that's easy to grow and just requires fertilization every month and to be always kept moist (misting is also good for it).

You can purchase this plant at most plant stores, or if you can get a Dieffenbachia on Amazon from various sellers.

 Some care tips:

1) Temperature: Keep between 65-80 degrees Fahrenheit.

2) Sunlight: It likes bright, filtered light such as what you find by a window.

3) Care and feeding: Keep soil evenly moist but not soggy. Feed monthly and keep away from drafts.

Corn Plant (Dracaena fragrans "Massangeana"): Best Air Cleaning Plant #12

The corn plant is a bit of a misnomer, as it has nothing to do with corn. But if you've ever shucked corn, you'll understand where the name comes from. The thick, green leaves that grow from the plant have a similar color, texture, and thickness as leaves you peel off of corn. In addition, the thick, round cane (main stem) of the plant is a solid woody stem with a light brown color that puts you in the mind of a corn husk or hull.

The plant is also known by a few other names, most commonly the cornstalk dracaena, the mass cane plant, or Dracaena fragrans. The latin name contains the word "fragrans" because when it grows in the wild it produces highly fragrant flowers. As a houseplant, though, it rarely blooms so most of the time it's grown as just a green plant.

You'll also hear the plant referred to as a "Mass Cane", which is short for "Massangeana Cane", one of the most popular variegated cultivars that you'll find in most shops--typically the variegation will be a yellow stripe down the middle of each left. Mine was supposed to be a Mass Cane, but it looks like it pretty much reverted to its original form as mine doesn't have any yellow stripes.

The plant is native to tropical Africa, from the Sudan to Mozambique to the Ivory Coast to Angola. There, they're generally grown as shrubs or hedge plants, as they thrive in the warm, wet climate. That same hardiness makes them practically indestructible houseplants. I speak from experience; I bought the corn plant you see here from 1-800-Flowers on September 18, 2009. Now, exactly five years later, the plant has survived a massive fungus gnat infestation, a repotting where the root ball was so heavy I accidentally broke most of it in the process, long periods of time without water (the soil would literally be dry to the point of cracking), and a spot in the house away from the window that gets no direct sunlight. While I had to trim a lot of it, and you can see a new offset growing at the bottom of the pot, the plant you see here is pretty much the same as I was five years ago.

It's a versatile plant as well. Some let the cane grow long and tall, while others will cut the cane and cap it, letting offshoots grow off to the sides (which is what I have here). The Janet Craig and the Warneckii cultivars we've already talked about all have their roots (no pun intended) in the dracaena fragrans.

This is probably one of the best plants for someone new to plants to grow, because it's virtually indestructible as long as you remember to water it every now and again. While it prefers bright light, you can put it in a part of the house that gets almost no light and it'll be just fine. The plant is exceptional at removing formaldehyde from the air.

You can purchase a 6" version at Amazon that you can grow from a small plant, or if you prefer a full-grown plant that's going to last years I'd suggest doing what I did and going to a site like Home Depot or 1-800-Flowers.

Areca Palm (Chrysalidocarpus lutescens): Best Air Cleaning Plant #2

The Areca Palm goes by a number of names: yellow palm, the butterfly palm. bamboo palm, or golden cane palm. It's native to Madagascar, where it grows in tropical rain forests or near moist river beds. It has since been naturalized to a number of islands near Africa, the Carribean, and Central and South America, basically any region that's tropical or subtropical and humid. And of course, it's one of the most popular houseplants in the world.

The Areca Palm is the only plant on Dr. Wolverton's list that gets a 10 out of 10 for transpiration--the rate at which it releases moisture back into the air. In fact, a 6 foot areca palm can release about one whole quart of water into the air every 24 hours, making it a great natural humidifier. Of course, this water has to come from somewhere, which means keeping watering it a LOT. You need to keep the root ball ball damp, mist regularly (at least daily), and provide humidity as much as you can, especially in a dry office or home environment (for example, putting it in a subirrigation planter or placing the planter on a bowl of rocks with water).

Ironically, while I talked earlier about how overwatering plants can cause excessive soil mites and fungus gnats, underwatering the areca palm can have the same effect, attracting nasties like spider mites, which thrive under hot, dry conditions.

Of course I can't talk about plants I buy at Kmart without finding something to complain about. And in this case, when I brought the Palm home I first notice a couple scale insects on the leaves (one pest I haven't had to deal with so far), which I immediately plucked off the plan. Luckily, it didn't look like an infestation, probably just a few that migrated over from neighboring plants. Again, great job by the Kmart in Manhattan.

After I got home, I noticed "freckles" (or if you prefer, "speckles" or "spots") all over the stems. Weirder still, I found that if I wiped them with a wet and slightly abrasive cloth (like a paper towel) they'd come right off.

I was perplexed as to what these were. I Googled it, and while I found a few others who encountered the same thing, no one seemed to know what they were. The one thing I learned is that people on the Internet love to talk about stuff they know nothing about. Some people swore these were more scale insects, but after a slight moment of panic I discounter this because they simply don't have the icky "bump" you generally see with scale. Others speculated that it's something called "flyspeck fungus". Some websites report that if you see spotting or speckling on leaves (but they didn't mention stems) it's an indication that there were salts or minerals in the water, as Arecas have the ability to move salt accumulations to selected branches (when the branches get saturated they'll die and you need to remove them, but the damage will be isolated to that frond). And others said this is just a natural phenomenon that happens with all Arecas. 

Just to be safe, I took a paper towel and some dish soap and scrubbed each of the stems. There's still spotting on them but it's a lot less than before.

I brought the plant to the office. Here's what it looks like right now: 

Arecas like indirect light, as direct sunlight can easily burn the leaves. I do have a corner of my office window that never gets direct sunlight, so I'll leave it there for a while. It helps that I have access to spring water outside my office, so I'll use that to water the plant to prevent it from having to deal with things like fluoride and salts in tap water.

My next step is going to be to repot it; while Arecas are okay being pot-bound, the current pot is too small for it to grow from its current height of about 2 feet to its standard indoor size of 6-8 feet (outdoors it can grow to 25 feet). This would require a pot that's about double what I have now.

As for the air-cleaning properties of the plant, this one ranks near the top. It removes benzene, formaldehyde, and trichloroethylene from the air.

If you're interested in an Areca Palm, this seller on Amazon is selling them, and of course you'll find them in most home centers and plant stores.

Some care tips:

1) Temperature: Keep between 65-75 degrees Fahrenheit.
2) Sunlight: As much light as it can get without getting direct sunlight. 
3) Care and feeding: Keep the root ball damp but avoid having the pot sit in water, which can cause root rot. Mist frequently to keep a good appearance. keep spider mites away, and give it the humidity it craves and will pay back in the form of great transpiration. 

UPDATE: sadly, I didn't take my own advice. I went on a two week vacation and forgot to tell anyone to water my plant, so I came back to my Areca slumped over and dried out to the point of being brittle. No great loss, as I figure next time I'll buy it from Amazon or Home Depot or somewhere other than Kmart. I'll post pictures when I get my new Areca in.

Dracena "Janet Craig" (dracena deremensis "Janet Craig"): Best Air Cleaning Plant #13

As much as I hate Kmart for the fungus gnat infestations, I do like the fact that they keep sending me free money to use. And so, with the proper precautions, I'll still buy houseplants from them.

I was surprised to see a Dracena "Janet Craig" among the plants they were selling. Of all the Dracenas, this is the one that Dr. Wolverton identified as the best of the best in the dracaena fragrans family for clearing the air, and one of the best plants overall for removing trichloroethylene (TCH). It made it to #13 of my edited list of best air-cleaning plants.

The plant is beautiful, with shiny dark leaves that look much richer and fuller than its close relative the Warneckii (both are cultivars from Dracaena fragrans). There are varying opinions about its origin; some say it comes from Puerto Rico, while others say that it's from the Canary Islands, Africa, Asia, or Madagascar.

It's said to be a very forgiving plant, able to tolerate neglect and low lighting conditions. This particular variety is the "comapacta", which reaches a height of only 1 to 3 feet and grows slower than the regular variety.

If you had to choose just one dracena variety for air purification, this is the one to get. Since they're really popular you can usually find them at places like Home Depot, or find one on eBay.

The last question I have about this plant is--who exactly was Janet Craig? I dug and dug for this answer, but can't find it anywhere. What I did find was that this cultivar was patented on December 27, 1999 and that the inventor's name is James E. Shank, and the plant was discovered in 1995 in Costa Rica, growing on an ornamental plant farm.  I didn't even realize that plant varieties could be patented, nor that it was just 16 years ago that this plant first came onto the market--and has since become one of the most popular houseplants around. "Her" full name according to the patent is "Janet Craig Gomezzi", but there's no indication of who this was; my guess is that it was just a personal friend of the inventor. But whoever she is or was, she'll live on forever now through the thousands of these houseplants scattered around the world--and in my office window.

Some care tips:

1) Temperature: Keep between 60-80 degrees Fahrenheit.
2) Sunlight: It likes partial shade or shade. Medium indirect lighting is best. 
3) Care and feeding: Keep soil evenly moist but not soggy, and don't let the root ball dry. Feed every two weeks in the spring and summer. Water less often in the winter and wipe off leaves when they get dustry. 

Red-Edged Dracaena (Dracaena Marginata) a.k.a. Dragon Tree: Best Air Cleaning Plant #20

Next on the list is the red-edged Dracaena, or dracaena marginata. Dr. Wolverton's book, he calls it the "Dragon Tree".

This is a lovely plant with narrow green leaves that have a deep green color and a red edge. Like other plants in the Dracaena family, it hails from Madagascar and other parts of tropical Africa. It's a hardy plant and supposedly one of the easiest to grow in the Dracaena family (although I find the Warneckii super-easy to grow too).

I purchased this one from Kmart, and like most plants I buy at Kmart, it was cheap and clearly in need of some TLC; there were fungus gnats in the soil, the tips of the leaves were drying out, and the color in the leaves were light and in some cases spotty. Still, like Charlie Brown and his tree, I figured, "Maybe all it needs is a little love".

I transplanted it into a larger pot, loosened the root ball, planted it in some good Miracle Gro potting soil, and gave it a good watering, but soon practically all the leaves had brown tips.

Dr. Wolverton gave some advice about the Warneckii that I believe I need to follow here with the Marginata: "trim dead tips with scissors, taking care to retain their natural shape".

I took his advice, and also his advice to make sure the soil was always moist but not soggy. Hopefully that should help the entire plant, from root to tips, take up the moisture properly. 

As for air cleaning, Dr. Wolverton rates this a 6/10 for chemical removal and a 7/10 for transpiration rate. He says it's among the best plants for removing xylene and formaldehyde. 

Some care tips:

1. Temperature: Keep between 60-75 degrees Fahrenheit. 
2. Sunlight: It likes partial shade. 
3. Care and feeding: Keep soil moist. Feed regularly in spring and summer with liquid fertilizer or a good plant food like Osmocote Pellets

As a popular houseplant, you should have no problem finding one in a local garden store or Home Depot, or if you prefer there are plenty of Dracena Marginata plants for sale on eBay. 

Dracaena Deremensis (Warneckii): Best Air Purifying Plant #17

This seems to be another houseplant with an identity crisis, and it's largely due to the fact that it's a cultivar--a cultivated variation of a plant that's been bred to bring out desirable qualities.

In the case of this plant, it's in the genus of dracaena. Dracena, which comes from the Greek word meaning "female dragon" is a genus with about 40 different species that are native to Africa and parts of southern Asian and Central America.

This particular plant is in the species d. fragrans, also knows as d. deremensis. It's been bred to contain an attractive pattern and given the name "Warneckii". They also call this particular variation "limelight" after the color of the leaves; while other variations are completely green or have white stripes, this one has a beautiful dark green color in the middle and light, lime-color on the outside, resembling the colors of a lime.

This plant is closely related to other houseplants on the list such as the corn plant, which hopefully I'll be writing about soon.

The plant originated in Madagascar and thrives in other areas of tropical Africa such as Sudan, Mozambique, the Ivory Coast, and Angola. As with many tropical plants, it makes a great houseplant because it can survive brutal conditions and neglect.

It likes medium light, but can tolerate direct sunlight as well as low light conditions. As just one example, after I bought this particular plant I left it inside a plastic bag and unwatered for about a week, but lo and behold, the leaves didn't even start to wilt or turn brown.

As for air cleaning qualities, this whole genus of plant is a rock star, and is especially good at cleaning benzene from the air. According to the Center for Disease Control, air in general contains benzene from a large variety of sources, including tobacco smoke, gas stations, motor vehicle exhaust, and industrial emissions. Indoor air contains higher level of benzene than outdoor air, because in addition to all those sources you also add benzene found in glues, paints, furniture wax, and detergents.

Even low levels of benzene exposure can cause symptoms such as dizziness and headaches. With long-term exposure, it can cause harmful effects on bone marrow, decrease red blood cells, negatively affect the immune system, and lead to cancer or leukemia.

In Dr. Wolverton's ranking, this plant has a 6/10 effectiveness in clearing chemicals from the air and 8/10 transpiration rate, meaning that it can create relatively substantial air movement as water evaporates from its leaves.

Some care tips:

1. Temperature: Keep between 60-80 degrees Fahrenheit, although it will tolerate colder temperatures for short periods
2. Sunlight: It likes partial shade, but will tolerate both direct sunlight and low light levels
3. Care and feeding: Keep the soil evenly moist. Feed during the summertime but not in the winter. Water less often during the winter. 

If you like the look of my lemon and lime colored Warneckii, you can shop your local garden store or find great ones on eBay.

Golden Pothos (Epipremnum aureum): Best Air Filtering Plant #24

I'd published this post earlier naming it as the #1 air cleaning houseplant, since this is the plant that's cited at the top of most lists and the famous TED Talk. The problem is, according to Dr. Wolverton's studies, this plant isn't at the top of the list for either filtering of chemicals nor for transpiration rate. I believe the reason it's at the top of so many lists is because it's so danged easy to grow, and a beautiful houseplant that's growing like a weed is ultimately going to be a better air cleaner than a fussy houseplant that doesn't want to grow at all. So I'll lead with this post again, but we'll give it its real ranking number from the revised list, which is #24. 

The first plant I bought at K-mart was a Golden Pothos. It was $6.99 but thanks to a rare confluence of events with their Shop Your Way rewards program, I managed to get it for a whopping eighteen cents.

The scientific name is Epipremnum aureum (or Scindapsus aureus or one of 23 other names, depending on who you ask). Now the botanists among you may be wondering why it's called "Pothos" but under the genus Epipremnum instead of the genus Pothos. And that's because it used to be classified under that genus, but is no longer. And now you know.

Some people call this the "Money Plant" and thus get it confused with the "Money Tree Plant" (Pachira aquatica). That's a great houseplant too, but not quite the same.

I put this first in the list because it's the one that comes up over and over again in the NASA report. It was one of the best all-around performers, removing 73% of benzene from a sealed experimental chamber in a 24-hour period (the fifth-best on the list) and 9.2% of Trichloroethylene (7th on the list). This plant was featured in a TED Talk by Kamal Meattle as one of the three essential plants for cleaning the air.

According to Dr. Wolverton, this plant originated in the Solomon Islands. It's native to Pacific regions like Australia, Malaysia, Indonesia, China, Japan, and India. It's actually a highly invasive species, meaning that given the right conditions in a tropical jungle, it'll grow and grow and grow. In fact, when the species has been introduced in places where it's not indigenous like Sri Lanka, it's been known to cause severe ecological disruption. This is probably why it's also been given names like "Devil's Ivy" and "Australian Native Monstera" (from the latin monstrum, probably referring to the unusual appearance of leaves).

Of course, the very hardiness that makes the plant so invasive in the tropics is what makes it one of the most beloved houseplants here at home. If you're like my wife and your picture is on plants' post office walls as the #1 most wanted killer of plants, you'll be surprised at how easy it is to grow the Golden Pothos.

The plant itself is lovely. It has heart-shaped leaves that are green and speckled with yellow (ergo, the "aureum" or "gold" in its name).

As for ideal growing conditions, think of the jungle--it grows best when it's not exposed to direct sunlight but in an area of your home or office that has access to bright but indirect light. Let the soil dry out between waterings.

With very little care, your Golden Pothos will grow and grow and grow, limited only by the amount of sunlight you have and the size of your flower pot. And the more green you see, the more that plant will be pumping out clean oxygen for you and removing ickiness like benzene, formaldehyde, xylene, and toluene from the air.

One very important thing to note is that you should keep this plant out of the reach of cats, dogs, and children because of the presence of raphides (calcium oxalate) which can cause some nasty toxic reactions if swallowed. Raphides are actually tiny, microscopic needle-shaped crystals that botanists believe is a defense mechanism, like pricks on a cactus. To be safe, when pruning the leaves use gloves (the plant liquids can cause irritation), and absolutely do NOT ingest leaves or let animals or children do so.

If you're looking for a golden pothos, you can most likely find one at a local shop like K-mart, Walmart, Home Depot, or a garden store. If you're rather get one online, you can try this product on Amazon or look for one on eBay.

Some care tips:

1) Temperature: Keep between 65-75 degrees Fahrenheit. Never let it drop below 50 degrees.
2) Sunlight: It likes partial shade or shade.
3) Care and feeding: Let the soil dry completely between waterings. Feed weekly from March to August.

The Best Air Purifying Houseplants - For Real This Time

In my last post I shared with you my new obsession--finding the best air cleaning houseplants and putting them in my office.

The problem is that there are dozens and dozens of Web sites out there that claim to have the list of "the best" plants for purifying air, and it seems that none of these lists match. Worse, most of these lists (mine included) draw extensively from the 1989 NASA study. The problem is that most people who cite this list (myself included) just take the list of plants from the study without reading the study. Had they read the study, they'd realize that the house plants chosen for this study were chosen more or less at random, so while all of them were found to have some level of air filtering properties, this list hardly represents "the best".

As I mentioned, the scientist who headed up this study, Dr. B.C. Wolverton, wrote a book on the subject called How to Grow Fresh Air: 50 House Plants that Purify Your Home or Office. I went and bought me a copy on Amazon.

The book is absolutely fantastic, and gives as definitive an answer as I've seen anywhere on what the top air filtering houseplants truly are.

Something I loved about this book was that Dr. Wolverton goes into the science of how houseplants clean air in a way that's really understandable (unlike trying to read his NASA study, which admittedly wasn't intended for a consumer audience). For example, he does talk, in layman's terms, about the original study, but also provides some intriguing facts, such as:

• By far the most common toxin in the air is formaldehyde, particularly in office settings. Formaldehyde is found in resins; tobacco smoke; gas stoves; and consumer products from garbage bags to paper towels to fabrics to permanent press clothes to carpet backing and floor adhesives. It's also used materials such as particle board and plywood that make up office walls and furniture. Many have cited the increased us of formaldehyde as correlating to increased numbers of people with asthma, cancer, respiratory disease, and more. And we're not even talking about other pollutants like xylene, toulene, benzene, trichloroethylene, chloroform, ammonia, and acetone. The good news is, we don't need more chemicals to fight this, as the good Lord has already invented the perfect air filtration system.
• Some people believe that when plants absorb toxins from the air, when that plant dies the toxins will all return to the air. This is not the case--their studies showed that plants actually take airborne toxins and deliver them to microbes living around their roots, which then break down the toxin, literally "removing" them, not storing them in any way.
• Plants placed in a "personal breathing zone" (a 6-8 cubic foot of space near, say, your office desk, computer, or sofa where you watch TV) can add humidity, remove bioeffluents (pollutants humans expel from their bodies) and chemical toxins in the air, and suppress airborne microbes, resulting in better health!
• Plants also release phytochemicals that suppress mold spores and bacteria found in the ambient air. Research shows that rooms filled with plants can have 50-60% less airborne mold and bacteria than rooms without plants.
• Plants really do "breathe". The technical word for it is "transpiration", where water evaporates from plant leaves to create "movement of air". Transpiration rate is a vital factor in removing toxins. Many of the most effective houseplants in the list have unusually high rates of photosynthesis and unusually high transpiration rates. It's the perfect air filtration system, as carbon dioxide is removed from the air and the soil, pure oxygen is released into the air, and toxins are drawn into the leaf and moved to the root zone for microbes to break it down. 

In the rest of the book, Dr. Wolverton rates 50 houseplants using a rating system he devised that combines four elements: 1) its ability to remove chemical vapors, 2) its ease of growth and maintenance, 3) its resistance to insect infestation, and 4) its transpiration rate. If you'd like to see his full list ordered by this rating system, I definitely encourage you to buy the book, which also provides excellent scientific information about air cleaning plants and descriptions and great photos of each of the 50 plants.

Since I consider myself a pretty seasoned amateur horticulturalist (or so I like to think), #2 is less of a concern for me. And since I'll be growing my houseplants in an office environment where it's difficult for insects to get into unless they have a building pass, #3 isn't too much of a concern either.

So I've taken the liberty of re-ordering Dr. Wolverton's list to focus on the plants he rated most highly for #1, its ability to remove chemicals from the air and #4, the ability of the plant to more or less circulate air on their own.

Here's the re-ordered list:

1. Boston Fern (Nephrolepis exaltata "Bostoniensis") - Chemical removal=9/10, Transpiration=9/10
2. Areca Palm (Chrysalidocarpus lutescens) - Chemical removal=8/10, Transpiration=10/10
3. Bamboo Palm (Chamaedorea seifrizii) - Chemical removal=9/10, Transpiration=9/10
4. Kimberly Queen (Nephrolepis obliterata) - Chemical removal=9/10, Transpiration=9/10
5. Gerbera Daisy (Gerbera jamesonii) - Chemical removal=9/10, Transpiration=8/10
6. Florist's Mum (Chrysanthemum morifolium) - Chemical removal=9/10, Transpiration=8/10
7. Peace Lily (Spathiphyllum sp.) - Chemical removal=8/10, Transpiration=8/10
8. English Ivy (Hedera helix) - Chemical removal=9/10, Transpiration=7/10
9. Rubber Plant (Ficus robusta) - Chemical removal=9/10, Transpiration=7/10
10. Dwarf Date Palm (Phoenix roebelenii) - Chemical removal=9/10, Transpiration=7/10
11. Schefflera (Brassaia actinophylla) - Chemical removal=8/10, Transpiration=7/10
12. Corn Plant (Dracaena fragrans "Massangeana") - Chemical removal=8/10, Transpiration=7/10
13. Dracena "Janet Craig" (dracena deremensis "Janet Craig") - Chemical removal 8/10, Transpiration=7/10
14. Lady Palm (Rhapis excelsa) - Chemical removal=7/10, Transpiration=8/10
15. Ficus Alii (Ficus macleilandii "Alii") - Chemical removal=7/10, Transpiration=8/10
16. Weeping Fig (Ficus benjamina) - Chemical removal=8/10, Transpiration=6/10
17. Dracaena "Warneckei" (Dracaena deremensis "Warnecki") - Chemical removal=6/10, Transpiration=8/10
18. Dumb Cane (Dieffenbachia "Exotica Compacta") - Chemical removal=7/10, Transpiration=7/10
19. King of Hearts (Homalomena wallisii) - Chemical removal=7/10, Transpiration=7/10
20. Dragon Tree (Dracaena marginata) - Chemical removal=6/10, Transpiration=7/10
21. Dwarf Banana (Musa cavendishii) - Chemical removal=5/10, Transpiration=8/10
22. Dendrobium Orchid (Dendrobium sp.) - Chemical removal=7/10, Transpiration=5/10
23. Lily Turf (Liriope spicata) - Chemical removal=7/10, Transpiration=5/10
24. Golden Pothos (Epipremnum aureum) - Chemical removal=5/10, Transpiration=7/10
25. Dumb Cane (Dieffenbachia camilla) - Chemical removal=5/10, Transpiration=7/10
26. Spider Plant (Chlorophytum comosum "Vittatum") - Chemical removal=6/10, Transpiration=5/10
27. Dwarf Azalea (Rhododendrom simsii "Compacta") - Chemical removal=6/10, Transpiration=5/10
28. Red Emerald Philodendron (Philodendron erubescens) - Chemical removal=6/10, Transpiration=5/10
29. Peacock Plant (Calathea makoyana) - Chemical removal=5/10, Transpiration=6/10
30. Tulip (Tulipa gesneriana) - Chemical removal=7/10, Transpiration=3/10

And so, I thought I'd try to "reboot" this series of posts I'm going to make about plants that clean the air by focusing on Dr. Wolverton's latest list. As before, my goal is ultimately to get as many of these plants filling my office as possible and really getting the air clean and pure.

Using Dr. Wolverton's book and all those other Web sites out there reference, I'll share my own personal experiences about growing these plants and talk about which ones from my experience are easy and which aren't.

Air Cleaning Plants from the NASA study - My New Obsession

As I mentioned a few weeks ago, I'm taking a little break from the Aerogardening and waiting anxiously for the Niwa. In the interim, I figured I'd go back to my roots (no pun intended), leave (no pun intended) herb gardening for a while and branch (no pun intended) off into a new kind of indoor garden.

Specifically, my new obsession is buying houseplants that clean the air.

Now hopefully everyone remembers from elementary school how photosynthesis works. Plants take in carbon dioxide and release oxygen. As luck would have it, humans breathe in oxygen and expel carbon dioxide. We live in a world where we've chopped down trees and put up office buildings in their place. Not that there's a lack of oxygen, but one nice thing about having plants around is that you get your own, personal supply of free, unlimited oxygen as long as they're around.

We live in a world that's filled with pollution. Sure, things like the Clean Air Act have helped with the worst offenders, but when you think about it, we're still surrounded by chemicals. Walls in our offices and homes are painted, furniture is polished, smokers who have been banned from smoking in public places outside have been chased indoors (we call our next-door neighbor "Smokey the Bear"), all kind of chemicals are used in manufacturing and energy production and it all fills the air.

But one thing that's cool about plants is that they take in more than just oxygen. They also take in other pollutants that are harmful to humans, including benzene (a common solvent found in gasoline, inks, oils, paints, plastics, and rubber, known to irritate the skin and eyes and even cause chromosomal mutations and leukemia), formaldehyde (found in foam insulation, grocery bags, wrinkle resistant clothes, cigarette smoke, pressed-wood products, floor adhesives), and trichloroethylene (found in inks, paints, varnishes, adhesives). All of these chemicals are all around us in our homes and offices, and all of them can be harmful to health. But with plants, the more they breathe in, the less you do.

There was a NASA study done in Mississippi in 1989 called "A Study of Interior Landscape Plants for Indoor Air Pollution Abatement" that studied different kinds of common, household plants and identified the ones that were most effective in cleaning the air. You'll find Web sites like this and this with lists of these plants, but as your friendly neighborhood Indoor Gardener, I thought I'd go a step further, go out and purchase these plants for myself, and write a few posts on the best houseplants for air purification.

So here's what I'll be doing for the next few weeks. I'm going into my local K-Mart that always has a stock of common household plants, and I'll be buying one from the NASA list every couple of weeks and sharing with you photos and stuff I'm able to find out about the best air cleaner plants. My goal is over the next few months to have collected all of these plants and put them in the sunny window in my office or living room.

If you're interested in the full NASA list, here it is. The reason you might see different lists on different Web sites is that there were a couple different studies in 1989, each which used different plants. This is a complete list I pulled from NASA's final report from their original experiments.

1. Golden Pothos (epipremnum or scindapsus aureus)
2. Warneckei (dracaena deremensis "warneckei")
3. Marginata (dracaena marginata)
4. Mass Cane/Corn Cane (dracaena massangeana)
5. English Ivy (hedera helix)
6. Peace Lily (spathyphyllum "mauna loa")
7. Bamboo Palm (chamaedorea seifritzii)
8. Chinese Evergreen (aglaonema modestum)
9. Gerbera Daisy (gerbera jamesonii)
10. Janet Craig (dracaena deremensis "janet craig")
11. Mother-in-Law's Tongue (sansevieria laurentii)
12. Pot Mum (chrysanthemum morifolium)
13. Ficus (ficus benjamina)
14. Heart Leaf Philodendron (philodendron oxycardium)
15. Elephant Ear Philodendron (philodendron domesticum)
16. Spider Plant (chlorophytum elatum)

If you read the original paper from NASA, the experiment went something like this. For each test, they planted two identical, healthy individual specimens of each plant into two separate and sealed plexiglass chambers. They filled the chambers with a mixture of gases like benzene and thichloroethylene (TCE). They took a sample of the gas immediately, and then left the plants overnight in the sealed chambers. 24 hours later, they tested it again. They opened the chambers and removed the plants. The foliage was removed from one of these two plants. 

Remarkably, all of the plants in the study showed dramatic reductions of formaldehyde, benzene, and trichloroethylene.

Eight years in 1997, principal NASA investigator B.C. Wolverton, who published the original paper, ended up writing a book called How to Grow Fresh Air: 50 House Plants that Purify Your Home or Office featuring 50 houseplants that clean the air.

20 years after this original study, researcher Kamal Meattle presented a TED Talk called "How to Grow Fresh Air" that pointed out the three plants he determined were most important: The Areca Palm (chrysalidocarpus lutescens), the Mother-in-Law's Tongue (sansavieria trifasciata), and the Golden Pothos (epipremnum or scindapsus aureus).

 

 First plant coming up in my next post--the Golden Pothos.