A new pilot is about to launch in Modena, Italy designed to measure the long-term metrics of the installations on the city landscape. German start - up Green City Solutions has developed massive vertical planter boxes filled with air - filtering plants to improve air quality in urban areas . The planters are called CityTrees and offer the environmental benefits of up to 100 conventional trees , but at 5 % of the associated cost and with 99 % less space required . Each box is also equipped with a digital screen to allow the space to be used for viewing . Hong Kong , London , Paris and Dresden are among the handful of cities currently using CityTrees .
German start - up Green City Solutions has developed massive vertical planter boxes filled with air - filtering plants to improve air quality in urban areas . The planters are called CityTrees and offer the environmental benefits of up to 100 conventional trees , but at 5 % of the associated cost and with 99 % less space required . Each box is also equipped with a digital screen to allow the space to be used for viewing . Hong Kong , London , Paris and Dresden are among the handful of cities currently using CityTrees .