Urban green spaces mitigate the impact of human activities on the environment, contributing to the physical, chemical and bacteriological purification of the atmosphere, also serving as habitats for a number of both vertebrate and invertebrate species, etc. As the rate of urbanization in the world is constantly accelerating, cities are expanding beyond borders, to the detriment of green spaces. Even though the buildings are expanding in height, in the great megacities of the world, where there is a considerable deficit of land, the idea came to extend the green spaces in height. For example, such terms have appeared, such as: green roofs, hedges, green buildings, vertical gardens, etc. Despite considerable evidence that green spaces provide environmental benefits, certain plant species, during flowering, contribute to the disruption of the health of some people allergic to the pollen.