The Trees Portal

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

In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. 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 wider definitions, the taller palms, tree ferns, bananas, and bamboos are also trees.

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. The majority of tree species are angiosperms or hardwoods; of the rest, many are gymnosperms or softwoods. Trees tend to be long-lived, some reaching several thousand years old. Trees have been in existence for 370 million years. It is estimated that there are around three 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 much 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. (Full article...)

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A 19th-century carving of a tattooed Maori from kauri gum. The carving is owned and displayed by the Dargaville Museum, New Zealand.

Kauri gum is resin from kauri trees (Agathis australis), which historically had several important industrial uses. It can also be used to make crafts such as jewellery. Kauri forests once covered much of the North Island of New Zealand, before climate change caused the forests to retreat, causing several areas to revert to sand dunes, scrubs, and swamps. Even afterwards, ancient kauri fields and the remaining forests continued to provide a source for the gum. Between 1820 and 1900, over 90% of Kauri forests were logged or burnt by Europeans.

Kauri gum forms when resin from kauri trees leaks out through fractures or cracks in the bark, hardening with the exposure to air. Lumps commonly fall to the ground and can be covered with soil and forest litter, eventually fossilising. Other lumps form as branches forked or trees are damaged, releasing the resin. (Full article...)

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Gregory's tree, a large boab tree

  • ... that Gregory's tree (pictured), near Timber Creek in Australia's Northern Territory, bears inscriptions by 19th-century explorers and is registered as both a heritage place and an Aboriginal sacred site?
  • ... that the Balderschwang Yew is possibly the oldest tree in Germany?
  • ... that black truffles suppress plant growth around their host tree, creating an area that looks burned?
  • ... that root extracts from the tree species Pycnanthus angolensis can be used to treat parasitic infections, such as schistosomiasis?
  • ... that the lime trees of Duncliffe Wood are reputedly among the oldest living things in the county of Dorset?
  • ... that trees of the New Guinea genus Finschia have stilt roots coming off the trunk up to 1.8 m (6 ft) off the ground?
  • ... that in the early 1980s, a team of surveyors discovered the World War II-era Avro Anson Memorial near Clackline, Western Australia, which had been overgrown by shrubs and trees?

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Socotra dragon tree.JPG
A specimen at Dixsam plateau
Dracaena cinnabari, the Socotra dragon tree or dragon blood tree, is a dragon tree native to the Socotra archipelago, part of Yemen, located in the Arabian Sea. It is named after the blood-like color of the red sap that the trees produce. (Full article...)

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