Street trees

Street trees bring nature into cities and mitigate the impact of traffic in suburban areas and the countryside. In urban contexts, they beautify busy areas, serve as street furniture, and perform other very important functions.
They reduce the risk of flooding, since between foliage, branches, trunks and roots, they are able to absorb rainwater in a significant manner, especially when there are multiple rows.

Trees allow for air cooling, both because the foliage intercepts solar radiation and offers shade, and because it produces steam that removes thermal energy from the surrounding environment.

Plants contain carbon dioxide and various gases because the leaf blade is able to absorb the particulate matter released by motor vehicles, performing an important filter function and contributing to the containment of the ozone hole.

However, planting trees in the city cannot be considered a simplistic solution because trees can contain beneficial breezes and modify the humidity level of the area.
The choice of trees should therefore be evaluated on a case-by-case basis, examining the characteristics and extension of the area in which to place them, choosing the aesthetic and formal characteristics of the plants, such as the appearance of the crown, flowering, persistence of foliage throughout the year and it is also very important, in the design phase, to take into account maintenance, extension and characteristics of the root system to envisage evolutionary scenarios in the short, medium and long term.

The extension of the tree canopy must guide the right distance between plants, between plants and buildings and other human activities. It is also necessary to take into account how much the inflorescences, foliage or fruit generated, can affect the normal paths.
In fact, each plant has its own growth potential and therefore requires adequate space, both above and below. It is not uncommon for the roots to conflict with cable ducts and underground utilities, or for the foliage to generate problems with overhead lines such as electricity, telephone and street lighting.

The plants with the greatest expansion, such as oaks, limes and ash trees, reach a crown of 15 meters, alders, maples, hornbeams, can reach a crown of 10 meters, while plants of the Rosaceae family have a lesser extension. There are plants whose crown extension reaches up to 6 meters but with a columnar trend, such as cypresses.

Some plant parasites are present in urban environments because there is a lack of that relationship with nature that allows the containment of pathogens. To avoid that particular environmental conditions, climate changes or diseases cause problems to plants, it is better to use varieties of native species and carefully evaluate the use of exotic plants and their ability to acclimatize.
Furthermore, it is not only useful to design a good irrigation system, choice and positioning of plants, but also to foresee and plan the management of the tree heritage over time, because these are living organisms whose state of health must be monitored to prevent disastrous falls, avoiding, with imprudent pruning and radical amputations, worsening the living conditions of the plants.