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Air Pollution: How to Create an ‘Air Quality’ Garden

A recent poll commissioned by the Royal Horticultural Society (RHS) found that only 6% of the population in the UK are taking active steps in the garden to help improve air quality. In London, its much worse with only 4% of gardens planted with pollution in mind. While the main causes of air pollution need to be tackled at source – for example, by legislation such as the proposed ban on sales of new petrol and diesel cars and vans in the UK by 2030 – residents can also do their bit by choosing plants that help reduce the effects of air pollution.

A Phyto-Sensor Toolkit, developed by Citizen Sense, a project led by Professor Jennifer Gabrys at the University of Cambridge, is a detailed guide that offers advice on different plants, highlighting those that absorb “gaseous pollutants through their stomata, drawing in heavy metals through their roots, or channelling and depositing particulates in their leaves” – particularly helpful in polluted urban environments.  The Toolkit lists plants that are beneficial to air quality. These were trialled in 2018 in a low-emission garden outside the Museum of London. Plants with hairy and rough or waxy leaves can capture particulates more easily, reducing them by up to 60% and cutting nitrogen dioxide by up to 40%.

This list includes Yarrow (Achillea millefolium), Ladies Mantle (Alchemilla mollis), Silverbush or Shrubby bindweed (Convolvulus cneorum), Wallflower (Erysimum), Lavender (Lavandula), Coral Bells (Heuchera), and Ivy (Hedera helix) because of its plentiful leaves.

Some of the plants in the Toolkit help to monitor air quality; their leaves will wilt or show signs of damage if air quality is poor. Examples include Red Elder (Sambucus racemosa), which is sensitive to ozone and exhibits damage to leaves and growth; and Delavay Osmanthus (Osmanthus delavayi), which experiences leaf damage when exposed to sulphur dioxide.

A new RHS science paper looked at the effectiveness of hedges as air pollution barriers and estimated that the bushy, hairy-leafed Franchet’s Cotoneaster (Cotoneaster franchetii) was 20% more effective at trapping harmful airborne particles in traffic hotspots than other shrubs. Professor Prashant Kumar, founder and director of GCARE at the University of Surrey, says: “The high particle capture during peak-traffic hours at around the breathing height of children compared with adult-breathing height reinforces our advocacy for the implementation of hedges as a barrier against traffic emissions, particularly around school boundaries, children’s play areas, and other vulnerable populations.”

The full article is available on DIY Garden.

Note: The plants identified in the article are suitable in a UK environment. Plants such as Cotoneaster and Ivy are identified as invasive species here in New Zealand. So be sure to check your local invasive species plant list before undertaking any planting.

[Source: Rachel Brown, DIY Garden, 5th April 2021]