The paper focuses attention to the issues of tree allées and tree-rows in the urban environment. Tree allées and tree-rows in streets are significant natural features of urban structures, linking the different areas of vegetation into a coherent system of urban green space. They belong to the most problematic and the most demanding objects concerning the greenery implementation and maintenance.
Tree-rows and tree allées in an urban environment as elements of street roads are usually part of road-side greenery. The road-side greenery has a specific status, specific functions, and also specific claims for setting-up and maintenance. It has a vital importance in the elimination of negative impacts of transport on the environment and at the same time it is strongly affected by transport. The quality of road-side greenery is usually much worse than the quality of park or housing estate greenery. The proposed planting of trees in street areas faces a number of barriers and restrictions, e.g. in terms of traffic safety (the distance of trees from kerbs), in terms of engineering networks (protection zones), in terms of heritage preservation (planting trees in protected areas of historic towns). The spatial aspect is also important – the possibility to join multiple functions, such as engineering networks, parking lots, sidewalks for pedestrians, cycling paths and planting of trees in street corridors. It means that the tree allées and tree-rows in streets belong to the most important but also the most endangered groups of green spaces in the urban environment. They suffer from drought, dust, air pollutants, salination, mechanical damage, and as a result of weakened vitality also diseases and pests.
The main activities in the care of green areas in the urban environment are keeping record of the quantity and condition of the existing greenery, planting and creation of new green areas, maintenance and protection of existing green areas. These activities are interrelated. Their goal is to keep the greenery as a whole in vital condition in order to enable it to perform its biological, social and other specific functions. Tree-rows and tree allées represent the significant space creating and nature-related elements, which facilitate improvement of the quality of public spaces in urban structures.