For those of us living in modern industrialised societies, the general trend has been to spend more and more time indoors: sitting in an office or cubicle behind a computer screen, or at home watching the telly or playing video games. With all these hours spent inside, there's less time for communing with the natural world: less time for hiking along a forest path, canoeing down a river, jogging along a beach, or even just sitting in a beautiful flower garden. As reported by ABC news:
"The number of Australians living in high-rise apartments doubled between 1991 and 2011, and that trend has continued since then. The quarter-acre dream is fast disappearing and larger blocks and family gardens along with it.
As more people move from country areas to the city and as land to build homes near the city centre becomes scarce, we're getting further and further away from nature. It turns out this isn't great for our health."
The Downside Of Indoor Living
The reason why it's not great for our health is twofold: First, we're missing out on all the proven health and wellness benefits of spending time in nature. In Japan, forest therapy or forest bathing (shin-rin-yoku) is a practice that in recent years has emerged out of an appreciation of the vital importance—for our physical and emotional health—of contact with trees and other plants. People who spend time regularly among the plants and animals of the natural world are, on average, happier and healthier than those that don't.
Secondly, the indoor spaces that we inhabit—viz. modern climate-controlled, air-tight buildings—tend to trap all variety of toxic volatile organic compounds (VOCs) within their walls. A poorly ventilated room or building traps pollutants that are off-gassed from paints, varnishes, synthetic fibers, and building materials, household cleaning products, and office equipment such as printers and FAX machines. Some examples of VOCs that are commonly present in our homes or offices include benzene, ethylene glycol, formaldehyde, methylene chloride, tetrachloroethylene, toluene, xylene, and 1,3-butadiene.
One solution is simply to make it a priority to spend more time outside. And this is good advice! But there's also a way that we can, at least to a certain extent, bring the natural world indoors—and that's by increasing the number of houseplants that we keep in our home and office.
At this point you might wonder: Do indoor house-plants really offer the same kind of health benefits as spending time outside, in a natural setting? And the short answer is: yes!
While filling your indoor spaces with an abundance of houseplants will never fully replace the need to spend time outdoors, there's lots of scientific evidence showing that having indoor plants in your home (as well as office, school, and health-care facility) can indeed support a variety of health benefits. Keep reading for all the interesting details on how exactly this happens.
Photosynthesis & Human Respiration: A Beautiful Symbiosis
Human respiration—the process of breathing—involves drawing in the oxygen-rich air (each time we inhale) which, in our lungs, is used to oxygenate the blood. This oxygenated blood fuels our cellular metabolism, which creates the energy required for our body to function. The waste product of this process is carbon dioxide, which we release back into the external environment, each time we exhale.
Our symbiotic relationship with trees and other plants has to do with the fact that during photosynthesis plants release oxygen, and convert atmospheric carbon dioxide into sugars. Photosynthesis and respiration are opposites in the sense that the by-product of photosynthesis is oxygen, while the by-product of respiration is carbon dioxide. So, metaphorically speaking, we could say that: what plants exhale, humans inhale; and what humans inhale, plants exhale. How beautiful!
This is particularly true during the daytime when sunlight allows photosynthesis to be happening. But what about during the night? As it turns out, plants during the night-time hours engage in a form of respiration similar to human respiration: drawing oxygen from the surrounding environment and emitting carbon dioxide. The good news is that plants produce approximately ten times more oxygen during the day (via photosynthesis) than what they consume at night—so the net effect of their presence is still highly beneficial.
What's more, as we'll see below, there are certain plant species that continue to release oxygen even during the night-time—making them an excellent choice for our bedrooms. But for now, let's take a slight detour, to explore some of the earliest scientific research on the benefits of plants, in a context that may surprise you.
Plants In Outer Space: Research On How Plants Absorb Toxins
Some of the earliest scientific research on the health benefits of indoor plants was conducted by the U.S. National Aeronautics and Space Administration (NASA), during their Skylab 3 mission to build an off-world outpost on the moon. What the scientists discovered was that their new high-tech space station was slowly filling with toxic VOCs—harmful fumes that would make long-term residence on the space station impossible. Since opening windows to let in some fresh air is not an option on a space station, the builders had to find another way to purify the air.
In their natural earth habitats, plants function as air purifiers, so the NASA scientists wondered if they could do a similar job in the enclosed environment of the space station. To test this hypothesis, the scientists constructed a test chamber and placed a variety of houseplants in it. Then they flooded the air in the chamber with toxic fumes and watched to see what would happen. As it turned out, the plants not only purify the air but also produced water vapour that helped to humidify the space. The NASA scientists had found the solution to their space-station conundrum, and it's a solution that you don't have to be an astronaut to benefit from :)
So how do they do it? Plants purify the trapped air by pulling contaminants into the soil, where root zone micro-organisms convert VOCs into food for the plants themselves. According to the NASA research, plants can remove as much as 87% of VOCs every 24 hours.
Plants Transmute Toxins & Improve Air Quality
The technical term for using plants to reduce or transform environmental pollution is phytoremediation: from the Greek root phuton which means "a plant." Happily, we don't have to actually remember this word to benefit from the ability of certain houseplants to purify our indoor environments—but it might be fun to know anyway.
In an experiment conducted by a team of scientists led by Vadoud Niri, and presented at a meeting of the American Chemical Society, the air of a series of sealed chambers was infused with eight common VOCs (e.g. acetone, benzene, and formaldehyde). The concentrations of these VOCs were then monitored by the scientists, over several hours, both with and without the presence of a given species of a houseplant—in order to determine whether and at what rate the specific plants absorbed particular toxins.
Though each of the five houseplants tested—bromeliad, dracaena, spider plant, jade plant, and Caribbean tree cactus—was effective at transmuting at least some of the VOCs, the overall winner in terms of VOC-scrubbing capacity was the bromeliad.
Expanding this list to include other top 20 air-purifying plants, gives you a wide variety of options for purifying your indoor spaces with houseplants, listed here in the order of their overall purifying performance:
- Boston fern (Nephrolepis exaltata Bostoniensis)
- Areca palm (Chyrsalidocarpus lutescens)
- Lady palm (Rhapis excelsa)
- Bamboo palm (Chamaedorea seifrizii)
- Rubber plant (Ficus robusta)
- Dracaena Janet Craig (Dracaena deremensis)
- English Ivy (Hedera helix)
- Dwarf date palm (Phoenix roebelenii)
- Ficus alii (Ficus macleilandii alii)
- Peace lily (Spathiphyllum sp.)
- Corn plant (Dracaena fragrans Massangeana)
- Golden pothos (Epipremnum aureum)
- Kimberly queen fern (Nephrolepis obliterata)
- Florists mum (Chrysanthemum morifolium)
- Gerbera daisy (Gerbera jamesonii)
- Dracaena warneckei (Dracaena deremensis warneckei)
- Dragon tree (Dracaena marginata)
- Schefflera (Brassaia actinophylla)
- Spider plant (Chlorophytum comosum)
- Weeping fig (Ficus benjamina)
Plants As Humidifiers: Moisturising The Air
As mentioned above, plants that purify the air can sometimes also humidify it. Such plants are a welcome addition to indoor environments made dry by air-conditioning or heating systems, or simply by their location within a desert-like climate. Examples of plants that release moisture into the air (i.e., act as natural humidifiers) include:
- areca palm
- Boston fern
- spider plant
- peace lily
- rubber plant
- Chinese evergreen
- snake plant
- dracaena marginata
- bamboo palm
Plants That Can Improve Sleep By Releasing Oxygen At Night
What we've learned so far: Certain houseplants (quite a few of them, actually!) do a great job of purifying the air—of removing harmful VOCs—and some plants also act as natural humidifiers. And all houseplants, during the daytime, increase the amount of oxygen in the air, via photosynthesis, which beautifully compliments our human respiration.
As mentioned above, many plants turn off their photosynthesis mechanism at night, so no longer release oxygen. Instead, they use a small amount of oxygen in their own respiration process and release carbon dioxide. This isn't a huge (or even medium-sized) problem since the amount of oxygen emitted during the daytime far exceeds the amount these plants use at night.
Nevertheless, it might be interesting and useful to know that there are some plants that continue to emit oxygen all through the night: Orchids, succulents, snake plants, and bromeliads do just this, making them a good choice to have in your bedroom, to support a better night's sleep by increasing oxygen levels at night as well as during the day.
Plants Increase Student Focus & Commitment
Indoor plants are beneficial not only in our homes but also in schools, where they've been shown to positively impact both attentiveness and attendance among students.
Research conducted by Amanda Read of The Royal College of Agriculture in Cirencester, England showed that students attending lectures in classrooms with indoor plants were much more attentive (with distractions reduced by 70%) in comparison to students in classrooms that had no plants. The same study found that students were almost 100% more likely to return to lectures in the classrooms that had plants in them than they were to return to lectures in a room without plants.
Plants In Offices Reduce Fatigue & Increase Productivity
Not surprisingly, the benefits of indoor plants apply to work as well as home and school settings. Several scientific studies have shown that having houseplants in offices reduces sick leave and Sick Building Syndrome while increasing concentration and productivity. Plants can also reduce office noise and alleviate stress.
Another study conducted by Norwegian scientists established that workers had fewer complaints of a cough, dry or itching throat, and fatigue when there were plants in the office. And experiments conducted in the Netherlands and England demonstrated that employees who worked in buildings with houseplants had better concentration, were more productive, and experienced greater job satisfaction than employees in offices without any plants. In short: plants in offices tend to make employees happier, healthier, and more productive.
Plants Enhance Post-Surgical Healing Process
Though people go to hospitals for the purpose of recovering from injury or illness, the incidence of iatrogenic disease suggests that hospitals—quite ironically-are not always the healthiest places to be, and sometimes quite the contrary. So any change in a hospital environment that has a positive effect is obviously a good thing. And as it turns out, there's evidence that plants in hospital rooms support the healing process. For instance:
One study found that surgical patients who recovered in rooms that had plants reported experiencing less pain, anxiety, stress, and fatigue than did patients who recovered from surgery in rooms without plants. Overall, the patients in rooms with plants had lower systolic blood pressure, were more satisfied with their rooms, and felt more positively toward hospital workers.
In another study, patients recovering from an appendectomy used fewer painkillers if they had plants in their rooms.
Plants As Natural Aromatherapy
Scientific studies have established the mental-emotional, psychological, mood-enhancing benefits of aromatherapy—the therapeutic use of scents—more than its physical benefits. Scents are processed via the limbic system, which is involved in emotion, memory, motivation, and learning.
But given the mind-body connection (e.g. Molecules Of Emotion by Candace Pert) it's not unreasonable to expect that certain physical improvement may well follow improvements in our mood, via the biochemical changes these initiates.
In any case, houseplants that release scents into the air can be a form of aromatherapy: creating a shift in mood that may also be associated with biochemical changes in our bodies. The scent of orange oil, for instance, has been shown to alleviate anxiety and depression. And the scent of lavender can induce a state of ease and calm.
Other fragrant houseplants—that may have aromatherapy benefits—include Spanish lavender, lily, jasmine, geranium, orange blossom, eucalyptus, Marino blue heliotrope, spearmint, Corsican mint, lemon balm, Crown Jewel gardenia, and rosemary.
Psychological Benefits Of Indoor Plants
As we just discussed, fragrant plants can enhance our mood via their effect upon our limbic system. But there are other ways that houseplants can bring psychological benefits. Flowering plants, for instance, tend to be really beautiful—and beauty in our living environment has an uplifting effect.
Indoor plants also provide an opportunity to care for another living being, as it grows and blossoms. The physical basics of caring for a plant—i.e. planting, watering, pruning, etc.—can have therapeutic value. It can help us unwind and relax after a long day or week. This is especially true if we choose a plant that we find beautiful and inspiring, and whose care requirements match our own level of commitment.
A well-cared-for plant can also become a potent symbol of growth and blossoming, restoration and rejuvenation, and the natural life-cycle of all living beings. Taking good care of a houseplant—like taking good care of a pet, or a human companion—gives us a purpose, and in this way can help to alleviate loneliness and depression.
House Plants Improve Acoustics
And finally, for all you music-lovers: One scientific study showed that plants can reflect, diffract, or absorb sounds, depending on the frequency – hence improving the acoustics of the room.
What Plants Can't Do
It's important to understand that while houseplants excel at removing VOCs and other gaseous compounds from indoor air, there are some indoor air hazards that they aren't able to clean up, for instance: particulates, dust, and radon.
Plants do, however, do a pretty good job with moulds and bacteria. According to Dr. B.C. Wolverton of the Environmental Laboratory of the United States John C. Stennis Space Centre:
"Plant-filled rooms contain 50-60% fewer airborne moulds and bacteria than rooms without plants."
One potential downside is that houseplants can carry allergens that certain people may react to—so just be sure you're compatible with the plants you choose.
Finally, while having indoor plants definitely makes those indoor spaces healthier, it doesn't replace the need to spend time outdoors, whenever this is possible: to commune with plants in their natural ecosystems. So even if you fill your home and office with houseplants (which we'd highly recommend!) do make time, also, to enjoy the forests, meadows, mountains, and seashore.
Therapeutic Dosage: How Many Plants Does It Take?
Once you're convinced of the benefits of houseplants, a natural question would be: How many of them do I need, in order to receive these desirable health benefits? Here are some reliable approximations:
The NASA researchers found that one larger plant per 9 square metres was sufficient to purify the air in a living space. This would translate, for instance, into using 15-18 plants in 15-20 cm diameter pots for a 167 square-metre home. You can achieve similar results with two smaller plants (10-12 cm pots) in place of one larger one.
To reduce fatigue and stress, and improve your overall health, place one large plant (20 cm diameter pot or larger) approximately every 12 square metres. In an office or classroom setting, try to position the plants so every student or worker has at least one in view.
In sum: One large plant (or two smaller ones) every 9-12 square metres is what the experts recommend.
The Bottom Line
The overall scientific consensus is that indoor plants can indeed improve your health. They accomplish this in a number of ways: by adding oxygen to the air; by removing toxins from the air; by humidifying the air; by emitting healing scents into the air; by providing an opportunity to care for another living being; and by simply being beautiful.
The investment required to add indoor plants to your home or office is a small price to pay for air purification that is both effective and at the same time naturally beautiful.
And many of the plants that you've learned about in this essay—that have been scientifically shown to improve physical and/or emotional health—are available to purchase, right here on our website.