WHAT TO LOOK OUT FOR

1 The Active Air Green Wall by Biotecture (biotecture.uk.com), a lush mix of ferns, ivy, Carex morrowii ‘Irish Green’ and Heuchera ‘Green Spire’, is an example of using technology alongside nature to improve city environments. Polluted air is cleaned by the roots and recirculated. Here it is expelled into the main tower to provide fresh air for those inside, and into the nearby water to help with oxygenation.

2 Phyllostachys edulis, the bamboo used by MOSO (moso-bamboo.com) to make the laminated, geodesic structures designed and fabricated by Xylotek (xylotek.co.uk), is a strong, fast-growing plant native to China. Some 20-25 per cent of the poles can be cut annually without reducing the size of a plantation, making it very suitable for reforestation.

3 Floating plants such as Nymphaea ‘Colorado’, which holds its salmon-pink flowers 7-10cm above the surface, help to keep the water cool by shading.

4 The deciduous conifer Metasequoia glyptostroboides, only known as a fossil until 1941, is now regularly used in planting schemes to help remove air pollution.