Initially the Green Cloister was conceived for rooftops to create pockets of green urban space for the enjoyment of urban dwellers. It is now recognised that the urban heat island effect is problematic and we need to find ways to cool down city regions (70,000 people died across Europe in the 2003 summer heatwave, most notably in Paris after which they pledged to plant one million trees for every million citizens). The recent response to tackle climate change has also been to plant as many trees as possible and seems to be a global movement as part of the solution to save the planet.
Trees can often not be planted due to underground service run locations, highway visibility splays, underground stormwater tanks, and on roofs and podiums it is impossible to supply sufficient root volume for trees to grow successfully. The costs involved to retrofit trees in vast expanses of existing tarmac/hard surface area are generally prohibitive.
Climbing plants however need a smaller volume of soil and yet are able to spread, if supported, and provide much needed canopy cover and shade.
Currently there is little data on the performance of climbing plants:
• firstly because everyone is focusing on the benefits of trees.
• secondly, because climbing plants have long been considered problematic byfacilities managers trying to keep their building facades and gutters clear of leaf litter and debris.
There are few examples in the UK of climbing plants being used to good effect in public/semi public spaces. Pergolas and archways adorned with climbers are most often in private gardens, with very few examples to be found even in National Trust properties.
The lack of use of climbing plants in the UK in the public realm can best be highlighted by the fact that Italian wholesale nursery growers near Pistoia have rows and rows of spectacular climbing plants ranging from two metres tall to 5 metres and mostly of species that would grow just as happily in the UK. Wholesale nurseries here grow very few climbing plants by comparison and rarely above one metre tall, with a concentration on self clinging climbers. This could change.
Climbing plants can not only contribute by reducing the urban heat island effect but also mitigate harmful emissions whilst increasing biodiversity. Planters are appearing at a vast rate across cities, as part of the pandemic response to separate cycle lanes and create outdoor areas for bars and cafes. However, the benefits are often only achieved by the surface area of the planter and the height of the plants (for example Bristol City Council have replaced much of the red and white plastic separation barriers with 0.5 x 1M Corten steel planters full of petunias giving an area of only one square metre of vegetation per unit and very little biodiversity).
The Green Cloister offers a much larger surface area of vegetation: horizontally with underplanting occupying the area of the planter; vertically in panels covered in climbing plants trained on wires; and a canopy that extends across adjacent hard surfaces to create a shaded area beneath. Different varieties of climbers have varying degrees of vigorous growth, density of foliage, seasonal variation, together with the ability to absorb harmful emissions and increase biodiversity
