titre: Planting scenarios
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id: plantingscenarios
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text:
## Planting scenario 1:
Street trees
Trees can help to improve air quality, while also enhancing biodiversity and reducing the urban heat island effect. Trees remove gaseous pollutants, and can capture particulates and phyto-remediate soils. However, trees planted on congested streets and in street canyons can trap gaseous pollutants and particulates at street level, and so planting location and design is important to consider in order to prevent these effects. It is important that clean air from above is able to circulate through to sites. Some trees also release higher levels of biogenic volatile organic compounds (VOCs), which are precursor gases that can form ozone. At certain times of year, some trees can also increase particulate levels through the release of pollen. The image here is based on a photo from Deptford Folk’s Evelyn 200 tree-planting project.
## Planting scenario 2:
Green walls and green screens
Green walls and green screens can be effective installations for trapping particulates. As the community garden examples demonstrate, an ivy screen at the boundary between a busy road and a playground can be one way to mitigate air pollution, with some studies suggesting reductions of up to 40% of particulates in the local area. Green walls can also reduce particulates, although they require more intensive preparation, installation and maintenance for the structure, growing medium and irrigation in order to ensure the plants do not die. The image here is based on a photo from the Edgware Road Tube Station Green Wall.
## Planting scenario 3:
Roadside planting
Roadside plantings, including shrubs, hedges, herbaceous plants and grasses, can provide barriers to roadside pollution for adjacent land uses. As one example documented in the image here shows, Hammersmith and Fulham Council has developed a Talgarth Road Green Corridor to shield cyclists from pollution generated by an adjacent roadway. Tall grasses have been planted to capture particulates, as well as absorb stormwater. Many of the plants illustrated in this toolkit make effective roadside plantings, some of which also take up and/or phyto-remediate soil contaminants.
