Why we Grow Houseplants


Edith Butler

At this time of the year gardeners dream and plan of warmer months and gardens to come but for all practical purposes we are limited to those plants we can tend inside. We all know that one rule for success is the right plant in the right place; for a plant to thrive they should be in an environment as close as possible to the one they evolved in. Yet our indoor environments are alien to all and downright hostile to many of our potted friends. For instance plant comfort levels average a humidity level of 85% whereas most homes have levels closer to 35% and often lower when heating and air conditioning are factored in. When we add to this lighting, watering and fertilizing needs as well as pest and disease problems one could question our persistence in bringing the garden indoors.

Apart from keeping gardeners sane over the winter months there are reasons long appreciated by everyone. Plants are inexpensive and beautiful decorations adding colour and life to cold dark days, windowsill herb gardens add taste to our cooking and aroma to stale air.

And now we have the results of studies by NASA and the Associated Landscape Contractors of America (ACLA) that show common indoor plants are a valuable weapon in the fight against indoor air pollution. NASA has carried out research for many years regarding biological processes of dealing with environmental problems here on Earth and in space habitats. Continuing on from this ACLA and NASA conducted studies on some common plants to determine their effectiveness in absorbing contaminants in the air. Plants were placed in sealed containers with chemicals that are found in modern homes and workplaces.

Three toxic chemicals used in these studies were:

Trichloroethylene, (TCE) is used in the dry-cleaning industry is also used in printing inks, paint, lacquers, varnishes and adhesives

Benzene is a common solvent present in gasoline, inks, oils, plastics and rubber. It is also used in the manufacture of detergents, pharmaceuticals and dyes.

Formaldehyde is found in almost all indoor environments; major sources include foam insulation, particleboard or pressed wood products. It is used in consumer paper products including grocery bags, waxed papers, facial tissues and paper towels. There are many other sources including heating and cooking fuels like natural gas, kerosene and cigarette smoke.

These chemicals have been found related to a variety of problems ranging from headaches, eye nose and throat irritation, allergic contact dermatitis, respiratory diseases, nervousness to diseases of the blood system including anemia as well as being considered carcinogenic.

The research has shown that living plants can go a very long way to removing these toxic chemicals from our air. Indeed in one NASA test a lowly spider plant cleaned 90% of the air borne toxins from a sealed room within 24 hours! Philodendrons and spider plants were the most effective in removing formaldehyde molecules whereas flowering plants such as chrysanthemums and gerberas excelled in removing benzene. Leaves, roots and soil bacteria were all found instrumental in removing trace levels of toxic vapours. If activated carbon is added to the potting mixture a living air cleaner is created. The plants absorb toxins and the carbon degrades the chemicals. Other top performers were English Ivy, Fig trees, Spathiphyllums and Dracaenas.

In the workplace plants are just as important, perhaps more so considering all the office furniture made of particle board as well as computer/photocopier paper and toner. Furthermore, the "Journal of Environmental Horticulture" published the results of a study conducted at Washington State University into the relationship between productivity and indoor plants. Two groups of people performed a stressful task on a computer; one group in a room with plants, one without. Interestingly the group with plants showed a productivity increase of 12 percent and a two percent lower blood pressure increase than the group without! Another reason to include greenery inside!

Any of us should be able to convince English Ivy, spider plants and philodendrons to survive in a window or several over winter. And now apart from all our traditional reasons to grow indoor plants we have solid scientific reasons to do so.