1 Definition
2 Overview
3 Distribution
4 Parts and function
4.1 Roots
4.2 Trunk
4.3 Buds and growth
4.4 Leaves
4.5 Reproduction
4.6 Seeds
5 Evolutionary history
6 Tree ecology
7 Uses
7.1 Food
7.2 Fuel
7.3 Timber
7.4 Art
7.4.1 Bonsai
7.4.2 Tree shaping
7.5 Bark
7.6 Ornamental trees
7.7 Other uses
8 Care
9 Mythology
10 Superlative trees
11 See also
12 References
Definition
Diagram of secondary growth in a eudicot or coniferous tree showing idealised vertical and horizontal sections. A new layer of wood is added in each growing season, thickening the stem, existing branches and roots.
Although "tree" is a term of common parlance, there is no universally recognised precise definition of what a tree is, either botanically or in common language.[1] In its broadest sense, a tree is any plant with the general form of an elongated stem, or trunk, which supports the photosynthetic leaves or branches at some distance above the ground.[2] Trees are also typically defined by height,[3] with smaller plants from 0.5 to 10 m (1.6 to 32.8 ft) being called shrubs,[4] so the minimum height of a tree is only loosely defined.[3] Large herbaceous plants such as papaya and bananas are trees in this broad sense.[1][5]
A commonly applied narrower definition is that a tree has a woody trunk formed by secondary growth, meaning that the trunk thickens each year by growing outwards, in addition to the primary upwards growth from the growing tip.[3][6] Under such a definition, herbaceous plants such as palms, bananas and papayas are not considered trees regardless of their height, growth form or stem girth. Certain monocots may be considered trees under a slightly looser definition;[7] while the Joshua tree, bamboos and palms do not have secondary growth and never produce true wood with growth rings,[8][9] they may produce "pseudo-wood" by lignifying cells formed by primary growth.[10]
Aside from structural definitions, trees are commonly defined by use, for instance as those plants which yield lumber.[11]