Trees have long been heralded the lungs of the planet, but increasingly plants are being deployed not just to absorb carbon dioxide, but to metabolise and reduce all manner of nasties from our ever-more polluted air. Plants act as an ecosystem ‘liver’ filtering pollutants such as sulphur dioxide and nitrogen dioxide through their leaves and roots, while dense canopied trees trap particulate material that might overwise find its way into our lungs and even bloodstream. According to a study in the British Medical Journal, nearly 9 million deaths a year are attributable to air pollution and up to one in ten lung cancers. And it’s not just our health that air pollution is damaging – according to the Woodland Trust, “nitrogen air pollution directly affects many plants and fungi. It strips trees of their protective lichens and causes a fertiliser effect where grasses out-compete more delicate woodland flowers. This disrupts woodland ecosystems in ways we are only beginning to understand”.
However, not all plants are created equal when it comes to detoxing. All plants absorb carbon dioxide and then there are ‘hyperaccumulators’, the real workhorses which can absorb high levels of pollutants without being poisoned themselves. They absorb pollutants through their roots then either storing them or converting them to less harmful chemicals or vapor which is released into the air in a process called phytoremediation. This breaking down of toxins, heavy metals and contaminates is a biohack that we can employ on a huge scale to clear up toxic wastelands and within our own homes and gardens. So which plants do it best?
Planting a tree of any species is a very good start. We need to plant 150 billion trees to achieve carbon neutrality by 2050 according to the Committee on Climate Change – if everyone put one in their garden, we’d contribute 22 million towards that goal. Aside from absorbing carbon dioxide from the atmosphere, trees also trap particulate matter in their canopies – and the bigger the canopy the more that they can trap. By the same logic, evergreen trees will be able to do this year-round, while deciduous will offer less protection in winter.
Don’t be afraid of planting a tree in a small garden – there is almost no garden that can’t accommodate a tree. If you’re in a town and your garden is on the smaller scale, consider a Hawthorn (Crataegus monogyna), whose rough leaves are especially effective at catching particulates, or an evergreen such as holly (Ilex aquifolium) or Yew (Taxus baccata). And think about where they are going – use them as a physical barrier between you and the road. Bigger gardens might be able to accommodate a beautiful Ginkgo biloba, or a Hornbeam (Carpinus betulus) or Lime (Tilia cordata).
Hedges are another fantastic way of incorporating pollution absorbing plants into the garden as well as forming a physical barrier between you and the road. Yew would be fantastic for this, or super shrubs such as Cotoneaster franchetii which been found to be 20% more effective at absorbing pollution than others– just one meter of Cotoneaster franchetii is capable of absorbing the pollution created from a 500 mile drive. This could be planted in amongst an existing hedge, along railings or a wall along a busy road.
Vertical planting is a great way of adding pollutant-absorbing screening in a small space – common ivy is unbeatable for covering a wall quickly and efficiently – just one square meter square of ivy screening can remove 145 million particulates a day. Evergreen climbers such as Trachelospermum jasminoides will give the added bonus of a profusion of white fragrant flowers throughout the summer, while Clematis armandii will give your garden fragrance and flowers early in the season.
Even balconies can be transformed into air-purifying havens. Evergreens such as Osmanthus would be happy in a pot and provide year-round detoxification services, as would a Bay or Virburnum. The hairy leaves of a Lady’s Mantle, Alchemilla mollis, catch baddies while offering sprays of delicate lime green flowers and Wallflowers will do the same as well as delivering unbeatable late spring colour.
Even within the home you can use plants to combat the effects of toxic air pollution. House plants such as Mother-in-Law’s Tongue will quietly release oxygen at night and is one of the best for filtering chemicals such as formaldehyde in the air. Spider plants do battle with carbon monoxide while Boston Ferns will metabolise ammonia.
As we become increasingly aware of the toxic effects of modern life, once again plants provide simple and practical solutions that deliver results and joy simultaneously.
