American Mountain-ash is relatively small (maximum height 40 feet) deciduous perennial tree, native to northern North America. Its conspicuous white spring flowers and outstanding, persistent orange fruit make it one of our most recognizable trees. (1) It is well adapted to both coarse and fine soil textures, but has a low tolerance for drought or fire, and virtually no tolerance for salt aerosols. It grows best in full sun but can tolerate some shade.

The showy white flowers appear in early summer, and the abundant orange fruit appear in summer, persisting through winter. Fruit provides palatable browse for many animals and birds, but is not suitable for human consumption, except, perhaps for various folk remedies; the plant is not toxic. (1) (5)

The mountain ash and related species (most often the European Mountian ash, Sorbus aucuparia) are sometimes referred to in folklore as "Rowan" trees, but this use has almost disappeared from the modern lexicon. The rowans were thought by the Celts and other primitive peoples of The British Isles to have magical properties.

Trees are essential elements of livable communities and a healthful environment. They are not only beautiful, they carry out many beneficial environmental functions. Trees absorb carbon dioxide, the major greenhouse gas (up to 50 pounds per tree each year), and release oxygen. They shelter and provide nesting habitats for wildlife, retain moisture in soils, hold topsoil in place, and provide shade and cooling.

Trees also provide fruits, nuts, oils, and syrups; pulp for paper, cloth, and rope; and wood for innumerable products and heat. Trees provide both direct and indirect economic benefits. Air-conditioning costs are less in a tree-shaded home, and heating costs are reduced when a home has properly selected and placed windbreaks. Beyond energy savings, landscaping with mature trees increases the value of property.

Indirect economic benefits extend beyond the individual to the community or region. Customers pay lower electricity bills when power companies use less water in their cooling towers and fewer measures to control air pollution. Communities also save money if fewer facilities must be built to control storm water.

Trees make the world more beautiful. They add color, structure, height, and grace to our neighborhoods, parkways, and streetscapes. Trees also neutralize the harshness and stress of urban life. They enrich our lives. Our forests, woodlands, parks, and preserves help us feel more relaxed and serene. A day or even an hour in the woods can help us feel rejuvenated. Trees are magnets for wildlife, which also add beauty, value, and interest to our world.

City and suburban trees often serve several architectural functions. They provide privacy, frame views, and screen out objectionable sights. They reduce glare and reflection, direct pedestrian traffic, and provide background for and soften, complement, or enhance architecture or topography.
--From The Morton Arboretum "Go Green"