This is probably going to be one of the most controversial posts I write since I do not agree with what the media is putting out about houseplants purifying the air—especially orchids.
It’s a well-known fact that houseplants, orchids included, exchange carbon dioxide and release oxygen. Bloggers have turned this idea into an exaggerated affirmation, stating that having houseplants inside your house would automatically purify the air you breathe, increase the oxygen levels in your room, and reduce respiratory problems. That’s not true.
Do orchids clean the air and improve air quality? Orchids, being such slow growers, do not contribute to the benefits of purifying the air in a room. Faster growing plants have a higher contribution to cleaner air, releasing oxygen at a higher rate due to higher photosynthesis. The amount of oxygen released by orchids is detrimental in terms of actually purifying the air you breathe.
In this article, you’ll learn why.
The idea that houseplants could purify air has been published on the internet for more than ten years, but there is no evidence that this is actually proven and published.
Lack Of Sufficient Testing Neither Proves or Disproves Air Purification by Orchids
There is one study, done by NASA, where they wanted to study the efficiency of household plants on space stations to purify the air and if adding plants would be a sustainable way to promote good quantities of oxygen. In this study, no orchids were used experimental plants.
I’ll link the 30-page NASA findings below in a clickable PDF at the end of this article.
The household plants they tested (Bamboo palm, Chinese evergreen, English ivy, Ficus, Gerbera daisy, Janet Craig, Marginata, Mass Cane/Corn Cane, Mother-in-law-tongue, Peace lily, Pot mum, and Warnecki) are all low-light plants.
What NASA did discover was that the microbes in the potting soil (and this is not orchid bark—it’s normal soil since all the plants were household plants) did the majority of the air purifying—not the plants themselves.
If orchids purify the air, then I’m doing extremely well, Unfortunately, the benefits of having orchids have yet to be studied in terms of amounts of oxygen they release in the air and how much they purify.
NASA’s research debunked the idea that the plants were in fact doing the purifying.
This direct quote from the article says, “Early tests demonstrated that potting soil, after all foliage had been removed, was more effective in removing benzene than pots containing full foliage and soil.” (pg.13)
They tested three common alcohols used in home construction at that time (the article was published in 1989).
Only three were tested:
There are thousands of other pollutants in our modern homes that were not tested and need to be.
As far as I know, orchids are extremely sensitive to air pollutants. When placed near the presence of ripening bananas, avocados, and tomatoes orchids tend to swivel and die. This is due to the ethylene gas that ripe fruit can emit. Bud blast is common when orchids are placed in the kitchen. It would be interesting to redo the tests and verify that the most common household gases that are produced in our modern homes.
Back to what most internet orchid bloggers are saying without actually reading the research they are stating… In the NASA findings, after retesting the air in the sealed container in 24-hours after the pollutant was injected, the highest percent of Benzene was removed by Gerber Daisy (67.7%); Trichloroethylene by Pot Mum (41.2%), and Formaldehyde by Mass Cane (70%). When computing all three components together, and not just isolated pollutants, the best air purifying plants was the English Ivy (89.9%).
The evidence was conclusive that the plants absorbed these pollutants. So, most gardening and flower bloggers started avidly smashing the keypad as words elaborately formed heated phrases on their websites. Most mention that all plants purify the air up to 90%, orchids included, and argue that adding a plant here or there in your living room will help you breathe better.
NASA never proved that.
The test also says at the end of the article, which most all readers seemed to skip over, is that for every pollutant that was absorbed in the beginning, a part of it was released back into the atmosphere after some time. This is referred to as off-gassing. I didn’t hear anyone stating that on their “Houseplants Can Cure Asthma” posts…
NASA tested first the plants with all the leaves, then later, the plants without bottom leaves. The plants with a few leaves on the top of the plant, leaving the open potting soil exposed to oxygen had the highest rates of air purification than fully leaved plants.
They explained this by the presence of bacteria and fungus that fed on the pollutants and contributed to better air quality. On page 15, they state that “These are common soil microorganisms and most are known to be capable of biodegrading toxic chemicals when activated by plant root growth.”
When they tested only the potting soil, they found that the soil without any sort of plant had better results than the fully leafed plant. When the soil had activated carbon in the formula, the results were even better. So further studies just kept showing that the plant doesn’t do the majority of the air purifying—the potting soil and its little bugs do.
Again, since this was not tested on orchids, there are no findings that the orchids do any better or worse. Since orchid’s substrate is not soil, there is no scientific evidence that orchids purify the air in a quantity that has any effect on your health or the levels of oxygen they produce.
The one positive conclusion I can make is that if you have activated carbon or charcoal in your potting medium, then that will in fact contribute to higher rates or air purification. There are plenty of studies on that, and you can read them in this article about adding charcoal to your orchid potting mix.
Another article written by Jane Tarran , Use Of Living Pot-Plants To Cleanse Indoor Air – Research Review published in Sydney Australia, states that “An evaluation of these studies is presented, plus novel research showing that potted-plants can also remove indoor CO and, sometimes, CO2. The evidence overall clearly shows that the potted-plant microcosm represents an innovative technology for solving indoor air pollution, which can otherwise cause a range of adverse health effects, including ‘building-related illness’.” I’ll link that article in the end, too.
In their study, they also conclude that the bacteria in the potting soil is the main source of air purification. It’s not exactly the plant itself.
The end result is that the air is cleaner, so I guess it’s better to praise a plant in social media than it is a low-life bacterium.
After all, I’m trying to kill the majority of the bacteria in my orchids. Why praise the little dudes?
How Many Orchids Does it Require to Clean the Air?
Another point to ponder is that the study does not actually portray our living rooms or home offices. NASA’s experiment was done in a small biosphere no larger than my computer desk and was crammed with plants. To recreate their results, I’d have to live in a jungle with more than 80 plants in each room, or just move my home office into a greenhouse—wouldn’t be a bad idea if I had one.
It has been proven that household plants release relatively 22 L of oxygen into the atmosphere for every 150 g of growth. This means that faster-growing plants will release more oxygen.
If you’ve grown orchids and I assume you have, you know that orchids are extremely slow growers (except Catasetum that spurt out like crazy when they come out of dormancy).
Most all other orchids are extremely snail-paced. For orchids to grow 150 g, it takes months.
Now calculate how much oxygen you breathe in a day: 550 L. Yep, that’s right. I won’t argue that orchids don’t clean the air—they do—or that orchids don’t release oxygen—they do.
But the quantities we’re talking about here are minimal. To actually promote a decent oxygen percentage into the atmosphere (and I’m talking about a house of 1,2000 square feet) you would need anywhere around 380 large plants to 750 small plants.
I’m not the only one here to argue this point of view. John Girman, from The National Geographic is a former senior science adviser at the U.S. Environmental Protection Agency’s Indoor Air Division calculated that it would be necessary to have 680 household plants to replicate the same benefits that the NASA experiment came up with.
So, in conclusion, orchids will clean the air and purify it and whatnot… but it’s effect in my overall respiratory wellness doesn’t even come close. There isn’t the even slightest extent that it would make any difference to humans. One study showed that if you had a jungle in your office, you could raise the oxygen levels from 20.9% to 21%.
The difference you smell when inhaling in a room with houseplants and orchids is the increased relative humidity in the air. This is a whole different point that deviates from this article. If you want cleaner air, then houseplants do make a difference, but going outside and taking a walk on a hiking trail is a thousand times better.
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Don’t just take my word for what is written here. Continue researching other articles about orchids purifying the air, because everyone has a different point of view and unique techniques that work for them. Here are a few other articles from other websites if you’d like to continue your research on oxygen levels produced by orchids:
– “USE OF LIVING POT-PLANTS TO CLEANSE INDOOR AIR – RESEARCH REVIEW” written by Jane Tarran, talks about the benefits that come from indoor plants, but the study shows that the potting medium is responsible for the majority of the air exchange.
– “Interior Landscape Plants for Indoor Air Pollution Abatement” written by B.C. Woverton, and published by NASA. I forgot to mention that the project was conducted with the participation of the Associated Landscape Contractors of America (ALCA) and this has caused some people to question the findings. Of course, all the landscape contractors would want the article to say plants improved oxygen, but since that is not what they said, this conspiracy theory has been thrown out.
In all, orchids improve the overall wellness of my life, whether or not they do or don’t increase oxygen or purify the air, they make me happy. So for me, it’s a done deal.
**Pauses sadly, then smiles with a twinkle in my eye** Time to go shopping! Happy Cultivating!