Caring For A Killer? Are Indoor Plants Harmful At Night?
For all the benefits that houseplants are acknowledged to provide us, one such question that continues to persist is ‘do indoor plants become harmful at nighttime?’
Whilst researching to help definitively answer this question it became apparent that the intent of folks typing this query into Google was to understand a little bit more about the gaseous exchange that occurs in plant tissues. And in particular the absorption and production of carbon dioxide.
They were not so concerned about plants becoming harmful by going on the attack under the cover of darkness ala ‘The Day of the Triffids’.
It’s well known that during daylight hours chlorophyll in plant tissues converts light energy and water, via the process of photosynthesis, into sugars and oxygen. The sugars help the plant to grow whilst the oxygen is emitted into the atmosphere as a byproduct.
The uncertainty over whether houseplants are harmful at night is founded in the fact that in the absence of light, plants are unable to produce oxygen yet continue to respire and release carbon dioxide.
It’s this carbon dioxide production that has many folks looking for assurance that it’s safe keeping indoor plants in the bedroom and that no ill effects will be suffered by sleeping next to them.
Fortunately for all nature lovers the concern that indoor plants elevate carbon dioxide to an unhealthy level during the night is unfounded.
How much carbon dioxide do plants emit at night?
Defining what volume of carbon dioxide is emitted by indoor plants is challenging as they absorb CO2 (photosynthesis) and release it (respiration) simultaneously.
Complicating our quest to answer how much carbon dioxide is released at night is the fact that following the loss of sunlight, absorption of CO2 doesn’t just stop instantaneously, it gradually reduces as photosynthesis slows to a halt. And as for respiration, well it continues in all cells day and night.
What we do know is that over the course of a whole day indoor plants will take in more carbon dioxide than they express. This can be proven simply by the fact that plants grow and carbon, taken from carbon dioxide, forms the main building block within their tissues.
In theory then you’ll actually be creating cleaner air by filling a room with as many plants as possible.
When looking into quantifying the influence of house plants on indoor CO2 one study discovered that when light energy is available, 1m2 of leaf surface had the effect of reducing carbon dioxide in a 1m3 enclosed space by 80% in just one hour!
Now it’s a little difficult to relate this data to a real world scenarios such as a bedroom but to give you at least some idea, 1m2 of leaf surface area is roughly equivalent to about 2 x weeping fig plants or 4 x spider plants.
So, is it unhealthy to sleep with plants in the room?
It’s perfectly safe to sleep in a room full of indoor plants. In fact in addition to barely increasing the carbon dioxide concentration some plants even continue to release oxygen during hours of darkness.
Moreover desert dwelling plants, such as sansevieria, have evolved to preserve water stores and only open their stomata for gaseous exchange during the night. Oxygen is expressed out into the atmosphere following a particular type of photosynthesis called Crassulacean Acid Metabolism (CAM).
If it is carbon dioxide that has you concerned then the contribution of house plants pales into insignificance when compared to our own respiration.
As a comparison, if you’re sharing a bed with someone you love, each breath they take exhales approximately 37mg of CO2.
Scaling that up, across the period of an 8hr sleep that equates to 300g of carbon dioxide being released, a mass greater than the entire weight of many small houseplants!
Luck comes in many forms, and there are indoor plants that deal with all different elements, from love, to money, and health.
From improved air-quality, to increased productivity at work, houseplants have the ability to improve our working days in multiple ways.