Clean air: save your home from harmful pollution with clever garden hedge choices

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Plant box and yew hedge, quercus llex and magnolia
Marianne Majerus
Alex Mitchell27 October 2017

You would have to have been living in an underground bunker for the past year not to know that London has a clean air problem. Over the past 13 months London Mayor Sadiq Khan has issued seven toxic air alerts.

The good news is that, though this may seem a problem beyond our control, we can make a difference in our gardens and outside spaces. The best thing you can do, particularly if you live on a busy road, is to plant a hedge.

The pollutants from vehicle exhausts disperse quite quickly once they move away from a road, so trapping them near the source and at exhaust pipe level really helps.

The denser the hedge, the better it is at “catching” tiny particles on leaves — from where they are washed off by rain — so they don’t end up in our lungs.

THE BEST ANTI-POLLUTION PLANTS

The best types of hedge for trapping air pollution are conifers because their tiny needle leaves have the greatest surface area, but steer clear of rampaging Leylandii which quickly becomes a monster and sucks all available moisture out of the soil.

A better bet would be the more manageable conifer Red Western Cedar (thuja plicata).

For a small London front garden hedge you can’t get much smarter than yew (taxus baccata). Dense, evergreen and with leaves made up of tiny soft needles, it is easily kept trimmed.

Yes, it has a reputation for being slow-growing, but if you only need three or four metres, why not splash out on some instant hedging? Hedges Direct sells 1.5 metre-high panels of ready-grown yew for just over £200 per metre-long panel.

Other good pollution-filtering instant hedges are Portuguese laurel, privet and lonicera nitida.

If you are prepared to wait for a hedge to mature, you can buy rootball or bare-root hedging plants for a fraction of the cost — we’re on the brink of bare-root season now, lasting until March, so this is a good time to do it.

WHICH TREES HELP TACKLE POLLUTION?

What about trees? We’ve all marvelled at the heroic London plane tree that seems to survive anything. They handled the soot of the Industrial Revolution and they can handle vehicle emissions today.

They “clean” themselves by shedding pollutants in their bark, which peels off regularly, giving them that beautiful camouflage effect.

Oddly though, latest research has found that planting trees on the sides of busy roads could actually make air pollution worse. In so-called “canyon streets”, such as Euston Road or Northumberland Avenue where high buildings on each side prevent wind from blowing away exhaust fumes, tree canopies can trap the pollution underneath.

Hedges, best between vehicle and cycle lanes to save cyclists’ lungs, would be much more effective. But in wide roads, parks or gardens, trees do a great job trapping pollution particles and absorbing toxic gases.

Best for gardens are maples including ornamental acers, silver birch, alder and conifers.

CAN I EAT PLANTS GROWN IN THE POLLUTED CITY?

When it comes to smaller plants, anything with little, hairy or rough leaves is good for trapping particles. And the great news for gardeners is that most of the plants recommended by a recent Imperial College study are already common garden favourites.

Anyone who has marvelled at the months of purple flowers from the perennial wallflower Erysimum “Bowles’s Mauve” will be delighted it makes the list. As does lavender, hebe, cistus, convolvulus and rosemary.

For a sunny front garden an informal hedge of lavender (try Hidcote for a compact shape and piercing purple flowers) or rosemary would make a beautiful screen if a traditional hedge is too tall.

Plant some hebes and erysimum, too, and intersperse with groundcover plants that make the grade, such as lamb’s ears (stachys byzantina) with their strokeable furry leaves, lady’s mantle and geranium maculatum, and you’ve created a pollution-busting front garden.

For shady spots, the hairy undersides of its leaves mean heuchera makes it on to the list, great for winter groundcover under trees and stunning in pots and window boxes.

You might think anyone who grows vegetables by the side of a busy road is mad. Especially by Brixton Road, which breached air pollution limits just five days into this year. But for architect and landscape consultant Deborah Nagan it didn’t stop her growing and eating vegetables from her front garden.

She’s not wrong. Research has shown that even in areas of high pollution particulates don’t get into the soil in enough quantity to be taken up by the plants. She recommends growing runner beans up the fence as a screen — but wash them before eating.

For instant hedging: hedgesdirect.co.uk

For perennials: crocus.co.uk