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.

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