A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by authors, varying from 3m to 6m, some authors set a minimum of 10cm trunk diameter (30cm girth). Woody plants that do not meet these definitions by having multiple stems and/or small size are called shrubs. Compared with most other plants, trees are long-lived, some reaching several thousand years old and growing upto 115m (379ft) tall.
Trees are important components of the natural landscape because of their prevention of erosion and the provision of a weather-sheltered ecosystem in and under their foliage. They also play an important role in producing oxygen and reducing carbon dioxide in the atmosphere, as well as moderating ground temperatures. They are also elements in landscaping and agricultural, both for their aesthetic appeal and their orchard crops (such as apple).
Koala Friendly Trees
Koalas are extremely picky eaters, however, preferring only a few types of leaves at a time, from the relatively small number of Eucalyptus species comprising their overall habitat. This fact had become particularly problematic in recent years as the destruction of their trees has been allowed to proceed at an alarming rate. There have been reports of Koalas occasionally eating leaves from trees other then eucalyptus, such as the Acacia costata, Bombas malabrica, Pinus radiate, Tristania conferta and Tristania suaveolens.