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Trees

Common ash (Fraxinus excelsior), a deciduous broad-leaved (angiosperm) tree

In botany, a tree is a perennial plant with an elongated stem, or trunk, supporting branches and leaves in most species. 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. Trees are not a taxonomic group but include a variety of plant species that have independently evolved a woody trunk and branches as a way to tower above other plants to compete for sunlight. Trees tend to be long-lived, some reaching several thousand years old. In looser definitions, the taller palms, tree ferns, bananas and bamboos are also trees. Trees have been in existence for 370 million years. It is estimated that there are just over 3 trillion mature trees in the world.

A tree typically has many secondary branches supported clear of the ground by the trunk. This trunk typically contains woody tissue for strength, and vascular tissue to carry materials from one part of the tree to another. For most trees it is surrounded by a layer of bark which serves as a protective barrier. Below the ground, the roots branch and spread out widely; they serve to anchor the tree and extract moisture and nutrients from the soil. Above ground, the branches divide into smaller branches and shoots. 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.

Trees usually reproduce using seeds. Flowers and fruit may be present, but some trees, such as conifers, instead have pollen cones and seed cones. Palms, bananas, and bamboos also produce seeds, but tree ferns produce spores instead.

Trees play a significant role in reducing erosion and moderating the climate. They remove carbon dioxide from the atmosphere and store large quantities of carbon in their tissues. Trees and forests provide a habitat for many species of animals and plants. Tropical rainforests are among the most biodiverse habitats in the world. Trees provide shade and shelter, timber for construction, fuel for cooking and heating, and fruit for food as well as having many other uses. In parts of the world, forests are shrinking as trees are cleared to increase the amount of land available for agriculture. 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.

Selected article

Bonsai at the National Bonsai & Penjing Museum at the United States National Arboretum.

About this sound Bonsai  (盆栽 Japanese) (lit. tray plant, from bon, a tray or low-sided pot and sai, a planting or plantings) is a Japanese art form using miniature trees grown in containers. Similar practices exist in other cultures, including the Chinese tradition of penjing from which the art originated, and the miniature living landscapes of Vietnamese hòn non bộ. The Japanese tradition dates back over a thousand years, and has evolved its own unique aesthetics and terminology.

'Bonsai' is a Japanese pronunciation of the earlier Chinese term penzai (盆栽). A 'bon' is a tray-like pot typically used in bonsai culture. The word bonsai is often used in English as an umbrella term for all miniature trees in containers or pots, but this article focuses on bonsai as defined in the Japanese tradition.

The purposes of bonsai are primarily contemplation (for the viewer) and the pleasant exercise of effort and ingenuity (for the grower). By contrast with other plant cultivation practices, bonsai is not intended for production of food, for medicine, or for creating yard-size or park-size gardens or landscapes. Instead, bonsai practice focuses on long-term cultivation and shaping of one or more small trees growing in a container.

Selected biography

Two Leg Tree

Axel Erlandson (December 15, 1884 – April 28, 1964) was a Swedish American farmer who shaped trees as a hobby, and opened a horticultural attraction in 1947 advertised as "See the World's Strangest Trees Here," and named "The Tree Circus."

The trees appeared in the column of Robert Ripley's Believe It or Not! twelve times. Erlandson sold his attraction shortly before his death. The trees were moved to Gilroy Gardens in 1985. Read more...

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The 1995 official White House Christmas tree

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