Monday, June 23, 2014

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.

golden pothos cleaning my office air

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.

Monday, June 16, 2014

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.

air filtering houseplants book

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.

plants that clean chemicals from the air

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.

Monday, June 9, 2014

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.

Tuesday, June 3, 2014

Buy Aerogarden Seed Kits Cheaper at Amazon

It's been a while since I ordered a new Aerogarden Seed Kit--actually I haven't gotten a new one since Miracle Gro made their investment in AeroGrow and started rebranding all the Aerogardens accordingly.

I just noticed that the new, re-branded herb kits are selling on Amazon, labeled as Miracle-Gro AeroGarden Gourmet Herb Seed Pod Kit (7-Pod).

It looks like they're pretty much the same old seed kits that they've been selling for years, although I notice they have a jar of liquid plant food now, a big improvement those awful plastic packets that always ended up drying out (to use them I'd always chop them up in a glass measuring up, stir to get the nutrients liquified again, and pour into my Aerogarden).

You can use the drop-down to choose from herbs, flowers, and vegetables. Here's the list as of today:

  • Gourmet Herb (which includes Genovese Basil, Thai Basil, Mint, Cilantro, Parsley, and Dill). This one never fails to get results and interestingly, they've removed Sage, Thyme, and Chives; those first two were always the trickiest of them to grow well. 
  • International Basil (Genovese, Thai, Globe, Lemon, Napolatino, Marseilles, and Red Rubin Basils). If you look back in the blog I grew this a couple years ago to fabulous results)
  • Catnip. You still can't grow that other medicinal herb in most states, but at least you can help kitty get her fix! 
  • Fresh Tea (including lavender, peppermint, lemon balm, and lemon mint). On my list to try some day. 
  • Italian Herb (Genovese Basil, Chives, Mint, Savory, Italian Parsley, Oregano, and Thyme)
  • Mountain Meadow (Deep Rose Gypsophila,Yellow Coreopsis, Orange Gazania, and Blue Brachycome)
  • Coleus
  • Petunia
  • Viva la Vinca
  • Lavender
  • Chili Pepper (Jalapeno, Red Fire, and Purple Super Hot peppers). Again, I had some really good results with these. 
  • Bell Peppers
  • Cherry Tomatoes (small, we've grown these before too)
  • Mega Cherry (slightly larger)
  • Heirloom Tomato (big, at least by Aerogarden standards)
  • Pesto Basil (just pods of Genovese Basil, nothing else)
  • Romaine Lettuce
  • Salad Greens (Red and Green Leaf, Butterhead, Romaine lettuces). If you recall, I tried these but it was a bit on the disappointing side. 
  • Salsa Garden (Red Heirloom Cherry Tomatoes and Jalapenos)
Pricing for these seed kits are around $15.95-$17.95, or roughly the same as on The nice thing about being on is that if you order two of them (or basically order anything else that adds up to $35), you'll get free shipping, which was always one of the things that killed it for me on the Aerogarden site. Aerogarden does honor the 100% Germination Guarantee--as you've seen in posts in the past, they can get a little technical with honoring this, but for the most part they'll be good about it. Also, if you're collecting free Amazon gift cards using a service like Bing Rewards (and if you're not, I suggest highly that you do), in just a few months you can earn enough points to trade in for multiple Amazon gift cards so you can get one for free!