Experts identify 'super-plant' that absorbs roadside air pollution.

Bushy variety of cotoneaster works best in areas of heavy traffic, say researchers, while other plants can cool buildings or reduce flooding.

Bushy, hairy-leafed cotoneaster is a “super plant” that can help soak up pollution on busy roads, horticultural experts have said.

Scientists at the Royal Horticultural Society (RHS) looked at the effectiveness of hedges for soaking up air pollution, comparing different types of shrubs including cotoneaster, hawthorn and western red cedar.

The study forms part of work by the charity to ease environmental problems such as air pollution, flooding and heatwaves, boosting the benefits of gardens and green spaces.

On roads with heavy traffic, the denser, hairy-leaved Cotoneaster franchetii was at least 20% more effective at soaking up pollution compared with other shrubs, the researchers said, though it did not make a difference on quieter streets.

The lead researcher, Dr Tijana Blanusa, said: “On major city roads with heavy traffic, we’ve found that the species with more complex, denser canopies and rough and hairy leaves such as cotoneaster were the most effective.

“We know that in just seven days a 1-metre length of well-managed dense hedge will mop up the same amount of pollution that a car emits over a 500-mile drive.”

She said cotoneaster would be ideal to plant along busy roads in pollution hot spots, while in other areas where encouraging nature was key, a mix of species would be recommended.

While a survey of 2,056 people for the RHS found that a third (33%) were affected by air pollution, just 6% are taking active steps in their gardens to alleviate it.

Of those surveyed by YouGov, 86% said they cared about environmental issues, while 78% worried about climate change, and the RHS is hoping to harness that interest to encourage people to think about helping the environment in their garden.

Prof Alistair Griffiths, RHS director of science and collections, said: “We are continually identifying new ‘super plants’ with unique qualities which when combined with other vegetation provide enhanced benefits while providing much needed habitats for wildlife.

“We’ve found, for example, that ivy wall cover excels at cooling buildings, and hawthorn and privet help ease intense summer rainfalls and reduce localised flooding. If planted in gardens and green spaces where these environmental issues are most prevalent, we could make a big difference in the fight against climate change.”

RHS scientists are now moving into the Hilltop centre, at the charity’s gardens at Wisley in Surrey, which has facilities that will allow them to increase research into these areas, as well as exhibition spaces and “living laboratory” gardens.

18 February 2021

The Guardian