Ī 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. Large herbaceous plants such as papaya and bananas are trees in this broad sense. Trees are also typically defined by height, with smaller plants from 0.5 to 10 m (1.6 to 32.8 ft) being called shrubs, so the minimum height of a tree is only loosely defined. 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. A new layer of wood is added in each growing season, thickening the stem, existing branches and roots.Īlthough '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. Because of their longevity and usefulness, trees have always been revered, with sacred groves in various cultures, and they play a role in many of the world's mythologies.ĭiagram of secondary growth in a eudicot or coniferous tree showing idealised vertical and horizontal sections. In much of the world, forests are shrinking as trees are cleared to increase the amount of land available for agriculture. Trees provide shade and shelter, timber for construction, fuel for cooking and heating, and fruit for food as well as having many other uses. Tropical rainforests are among the most biodiverse habitats in the world.

Trees and forests provide a habitat for many species of animals and plants. They remove carbon dioxide from the atmosphere and store large quantities of carbon in their tissues. Trees play a significant role in reducing erosion and moderating the climate.

Palms, bananas, and bamboos also produce seeds, but tree ferns produce spores instead. Flowers and fruit may be present, but some trees, such as conifers, instead have pollen cones and seed cones. The shoots typically bear leaves, which capture light energy and convert it into sugars by photosynthesis, providing the food for the tree's growth and development. Above ground, the branches divide into smaller branches and shoots. Below the ground, the roots branch and spread out widely they serve to anchor the tree and extract moisture and nutrients from the soil. For most trees it is surrounded by a layer of bark which serves as a protective barrier. This trunk typically contains woody tissue for strength, and vascular tissue to carry materials from one part of the tree to another. It is estimated that there are around three trillion mature trees in the world.Ī tree typically has many secondary branches supported clear of the ground by the trunk. Trees have been in existence for 370 million years. Trees tend to be long-lived, some reaching several thousand years old.

The majority of tree species are angiosperms or hardwoods of the rest, many are gymnosperms or softwoods. Trees are not a monophyletic taxonomic group but consist of a wide variety of plant species that have independently evolved a trunk and branches as a way to tower above other plants to compete for sunlight. In wider definitions, the taller palms, tree ferns, bananas, and bamboos are also trees. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are usable as lumber or plants above a specified height. In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. European larch ( Larix decidua), a coniferous tree which is also deciduous

Sunlight through autumn trees