Back in the late 80’s, the US government space agency NASA, teamed up with the Associated Landscape Contractors of America (ALCA) to determine if the humble indoor plant could help to purify the air in our homes. The Clean Air Study was particularly focused on the removal of benzene, trichlorothylene, and formaldehyde, all of which have been identified as hazardous to human health.
These three chemicals were the focus of this particular study, there are others and most of us are not familiar with all of their names but they all have some degree of negative health implication for humans – lung irritation, allergies, headaches and immune system depression to name just a few.
Of course, levels, duration and type of exposure are key factors, but remember many of these compounds are found in places we don´t necessarily suspect – building products (concrete, plaster, paints) treated fabrics (curtains, carpets, rugs) and urea-formaldehyde resins (UF) pressed hardpack wood (panelling, partition walling, MDF). How you heat and cook at home can also impact the quality of the air you breathe via the gases released, and most household cleaning products contain a myriad of chemicals which you inhale and also come into skin contact with.
During the NASA/ALCA study, they exposed various common house plants to these air-borne chemicals and the results found that some plants are more effective than others – which in itself is not surprising – what was surprising, is just how effective some of them can be in filtering and purifying the air. This purification wasn´t just down to plants with a full foliage of leaves either, the roots and soil also seemed to have an important role to play.
One thing to note about the Clean Air Study is that it was carried out under sealed conditions – i.e. no ventilation (a bit like space..) so even though effectiveness was shown, the conditions are not representative of how we live our lives down on Earth – we open windows, doors and generally have a flow of air in our homes.
Under these sealed conditions, common indoor plants from the genus Ficus (the family of plants that includes fig and rubber tree´s) were found to remove 47.4% of formaldehyde, 30% of benzene and 10.5% of trichlorothylene (measured in parts per million) over a 24 hour period. Overall, the Peace Lily ranked best – it was also effective at filtering others toxins like xylene, toluene and ammonia from the air.
According to the study, here are the top 10 plants (in no particular order):
- Fiddle Leaf Fig
- Boston Fern
- Peace Lily
- Devils Ivy
- Chinese Evergreen
- Spider Plant
- Weeping Fig
- Aloe Vera
- Areca Palms
- Snake Plant
As we spend a majority of our time indoors, its important to create and cultivate a space that´s not only beautiful, but healthy. Investing your time and energy into some plants will be rewarding in every way, so don´t be put off by past experience or think you don´t have time to look after a plant. We also know that being surrounded by nature is good for us, so it follows that being surrounded by and caring for house plants, has also been found to have a soothing effect.
The hardest part about having house plants is keeping them thriving – many a house plant has met it´s end at my hands but I´ve learnt a bit along the way so here are my tips for happy, healthy plants:
- The darker the leaf the less direct light tolerant they will be so filtered light will be best. If the plant has white or paler green marks in its leaf then it can handle more direct sunlight.
- Think about your placement – a Peace Lily, Fiddle Fig, Weeping Fig or Boston Fern will be great in the living room but just not next to a window that gets full sun. Whereas the Spider Plant tolerates direct light well and can also handle variations in temperature so its a good one for a sunny orientation. Generally most house plants wont thrive in windy spots, they also won´t like an air con blasting on them for example.
- Watering – many a houseplant has met it´s end from either a lack of water or overwatering. You´ve got to keep an eye on them and also check the instructions! I tend to water my smaller plants in the sink so they can drain properly, the one´s in ceramic pots I feel the soil and water if they need it – my Fiddle Leaf Fig I water once a week roughly but my Zanzibar Gem only about once every three weeks as it´s a very hardy plant.
- Plants need to eat not just drink. Nitrogen, phosphorous and potassium are all essential chemicals for your plant to grow, they only need feeing in their growth periods (spring and summer) and even then only every three months or so. You can even make your own plant fertiliser from left over food scraps.
- Clean their leaves. Once every few weeks just wipe the leaves down with a damp cloth (both side of the leaves), this way, they can ´breathe´ better.
- Bathrooms often tend to have less light and less floor space so think about hanging plants – Devils Ivy and Chinese Evergeen for example, they will also love the humidity and won´t need so much direct watering.
- Bedrooms are a wonderful space for a plant and I particularly love something like a Areca Palm or something more structural like a Snake Plant which is also unique for it´s night time oxygen production capabilities.