These give the impression of walls of greenery. The trees are allowed to grow freely upwards. They are pruned along the sides to create a green curtain which blocks out the wind, and which can offer shade during a walk. They are formed mainly from deciduous trees. Most commonly, plants of a single species are planted alongside one another, although this is not always the case. At Wilanów, they are formed from hornbeam, linden, and elm. They are home to many species of animals, as well as provide birds with a place for building nests.