Trees block out part of the sky, defining the sky's borders. Trees also contribute structure to the garden. Trunks and branches act as posts and beams to bring the sky down to a more human scale. For this management of the sky, trees have a purpose in every landscape, even the smallest one.
Trees have other uses as well. No other characteristic of trees is as obvious in the landscape as the shade they provide. Through their ability to filter sunlight and to cool the air through evapotranspiration, leaves can reduce the temperature by up to 10 degrees Fahrenheit on a hot summer day. Shade also protects from excess sun that can annoy your eyes and be dangerous for the skin. So every garden should have at least one shady nook. Some trees are known as "shade trees." These are usually taller trees with a broad crown. Smaller trees can also provide plentiful shade, although you may prefer to remove some of the lower branches for sitting
