Houseplant Appreciation Day is celebrated every January 10, particularly in America. It originates from people finding the gaping space left once the Christmas tree was gone unbearable.

Of course it’s quickly acknowledged that houseplants are more than something to fill a space and that’s where we’d like to start our appreciation. As all plants@work members know, houseplants are so much more than a green decoration and that‘s what makes them so perfect to celebrate and appreciate.

As well as refreshing the air and improving humidity levels, two years plus of Covid lockdowns has really shown how plants can help our mental health. Tending and caring for a plant or two really helped many people's stess levels during that period. Several research studies have shown that they can help reduce stress and even one plant can do this.

As we’ve already mentioned, plants also refresh the air giving us cleaner air to breathe which is good to know if you are working in an office with sealed windows.

Other studies have shown that having plants in your room, help to improve productivity – good news for businesses in particular – and they also help with creativity. These areas of research might seem obscure but they have been proven several times by different researchers.

There are many other things that plants do. We will cover some of these during this week.

Biophilia
Let's start with biophiliia. The concept was first recognised or publicised by Edward O Wilson, a Havard professor and Pulitzer prize winner twice over. Biophilia recognises our need to interact with nature; we function best when we can include views of nature and immerse ourselves in it. This was recognised by some of the early plant researchers though they didn't call it biophilia but they did acknowledge that we evolved in the natural world and after the industrial revolution and later the technological revolutions, we had come adrift from our roots.

How do we recreate biophilia in our homes and perhaps more importantly our places of work? Plants are the most obvious way to recreate a natural space but they aren't the only way. Natural light, views of the natural world beyond the walls of your office or workplace, natural materials like wood and patterns that reflect the wonderful natural world outside, all combine to create a biophilic area.

But plants are a very good place to start creating a natural feeling indoors.

From the Human Spaces Global Report
'Biophilic design is a response to the human need to connect with nature and works to re-establish the contact in the built environment. Ultimately, biophilic design is the theory, science and practise of creating buildings inspired by nature, with the aim to continue the individual's connection with nature in the environments in which they live and work every day.'

So why not invest in a houseplant or two to bring the outdoors in and get caught up in biophilia?

Houseplants cleaning the air
It was as long ago as 1989 that NASA first published their findings on plants cleaning the air of toxins. The basic principles are that during photosynthesis plants exchange oxygen which they expel for us to breathe, in exchange for carbon dioxide which they take in from the surrounding air. They also absorb harmful substances found in the air that are expelled by many different objects including car exhaust fumes, industry emissions, paper products, machinery such as photocopiers, carpets and upholostery, perfumes, deoderants and cleaning products being some of the biggest culprits.

NASA tested the plants under laboratory conditions using a huge number of plants; this doesn't reflect how we usually use plants in our homes or even most office buildings. So it is not surprising that whilst they can improve the air, the results may not be as effective as first reported in normal circumstances.

Plants affect the indoor environment in three main ways

First, the bacteria in the soil that live amongst the roots are able to break down some VOCs, and convert them into substances useful to the plants. This is an entirely natural phenomenon, although only relatively recently properly understood in horticulture. Plants with healthy roots and good soil will have the biggest impact, and those that are the fastest growing will also be the most effective.

Second, plants that are actively photosynthesizing will be removing some carbon dioxide from the air. Plants that originate in dark tropical conditions (such as rainforest floors) are able to photosynthesize extremely efficiently – they have evolved ways of making photosynthesis work even in very low light conditions, so that means more carbon dioxide is used by the plants.

Third, plants with hairy or slightly sticky leaves are able to trap particulates on the leaf surfaces, including fine particulates. In fact, plants such as ivy and Cotoneaster are used outdoors to mitigate the effects of pollution in urban areas. Some indoor plants can do that too (although they will need to be cleaned – there is no rain indoors to wash that pollution away). In fact, research carried out at Washington State University some years back showed that many different types of foliage plant attracted dust to their leaf surfaces – possibly as a result of an electrostatic effect – so almost any leafy plant will be useful.

Plants that are adapted to low light conditions will be the best to improve indoor air quality, especially reducing VOCs and carbon dioxide. Plants in the aroid family, such as Spathiphyllum, Philodendron species, Aglaonema species or Monstera species will be good, as will other jungle-floor plants such as species of Calathea, Ctenanthe and even small palms, such as Dypsis lutescens.

If light levels are slightly higher, species of Dracaena have been shown to be effective at reducing levels of carbon dioxide (experiments carried out in Australia by Margaret Burchett, Fraser Torpy and colleagues, in real office conditions have shown that relatively few plants are needed to have a measurable effect).

Thanks to Kenneth Freeman of Purposeful Places, our current chairman for this information about how plants work to improve our indoor air.

All plant images courtesy of The Joy of Plants

Houseplant Appreciation Week Stickers are available for members to use here.