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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, which 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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Betula pubescens (syn. Betula alba), commonly known as downy birch and also as moor birch, white birch, European white birch or hairy birch, is a species of deciduous tree, native and abundant throughout northern Europe and northern Asia, growing farther north than any other broadleaf tree. It is closely related to, and often confused with, the silver birch (B. pendula), but grows in wetter places with heavier soils and poorer drainage; smaller trees can also be confused with the dwarf birch (B. nana).

Six varieties are recognised and it hybridises with the silver and dwarf birches. A number of cultivars have been developed but many are no longer in cultivation. The larva of the autumnal moth (Epirrita autumnata) feeds on the foliage and in some years, large areas of birch forest can be defoliated by this insect. Many fungi are associated with the tree and certain pathogenic fungi are the causal agents of birch dieback disease. (Full article...)

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... that the Easter egg tree (pictured) in Saalfeld, Thuringia, was decorated with 10,000 Easter eggs in 2012?
... that the most popular species for Christmas trees in Denmark and most of Europe is the Nordmann fir?
... that seed of the African teak tree is largely dispersed by fruit bats?
... that Trichia decipiens live on deadwood of conifers and leaf trees all year around?
... that Aecidium mori causes mulberry rust disease on the mulberry flowering plant, which decreases the quantity of leaves on the trees?
... that the satinleaf tree is endangered in its native Florida, but an invasive weed in Hawaii?
... that the Brown Treecreeper spirals up and down tree trunks while foraging?

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Technician checks on genetically modified peach and apple "orchards". Each dish holds experimental trees grown from lab-cultured cells to which researchers have given new genes. Source: USDA.

A genetically modified tree (GMt, GM tree, genetically engineered tree, GE tree or transgenic tree) is a tree whose DNA has been modified using genetic engineering techniques. In most cases the aim is to introduce a novel trait to the plant which does not occur naturally within the species. Examples include resistance to certain pests, diseases, environmental conditions, and herbicide tolerance, or the alteration of lignin levels in order to reduce pulping costs.

Genetically modified forest trees are not yet approved ("deregulated") for commercial use with the exception of insect-resistant poplar trees in China and one case of GM Eucalyptus in Brazil. Several genetically modified forest tree species are undergoing field trials for deregulation, and much of the research is being carried out by the pulp and paper industry, primarily with the intention of increasing the productivity of existing tree stock. Certain genetically modified orchard tree species have been deregulated for commercial use in the United States including the papaya and plum. The development, testing and use of GM trees remains at an early stage in comparison to GM crops. (Full article...)

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General images

The following are images from various tree-related articles on Wikipedia.

Image 1A forest near Vinitsa, North Macedonia (from Forest)
Image 2Informal upright style of bonsai on a juniper tree (from Tree)
Image 3Wind dispersed seed of elm (Ulmus), ash (Fraxinus) and maple (Acer) (from Tree)
Image 4Alnus glutinosa (from List of trees of Great Britain and Ireland)
Image 5Fraxinus excelsior (from List of trees of Great Britain and Ireland)
Image 6Garibaldi Provincial Park, British Columbia (from Forest)
Image 7Share of land that is covered by forest (from Forest)
Image 8A section of yew (Taxus baccata) showing 27 annual growth rings, pale sapwood and dark heartwood (from Tree)
Image 9The General Sherman Tree, thought to be the world's largest by volume (from Tree)
Image 10Roof trusses made from softwood (from Tree)
Image 11Rowan tree in Wicklow, Ireland (from List of trees of Great Britain and Ireland)
Image 12Common ash (Fraxinus excelsior), a deciduous broad-leaved (angiosperm) tree (from Tree)
Image 13The Amazon rainforest alongside the Solimões River, a tropical rainforest. These forests are the most biodiverse and productive ecosystems in the world. (from Forest)
Image 14World production of selected forest products (from Forest)
Image 15Malus sylvestris (from List of trees of Great Britain and Ireland)
Image 16Proportion and distribution of global forest area by climatic domain, 2020 (from Forest)
Image 17Buttress roots of the kapok tree (Ceiba pentandra) (from Tree)
Image 18Temperate rainforest in Tasmania's Hellyer Gorge (from Forest)
Image 19Conifers in the Swabian alps (from Tree)
Image 20Latex collecting from a rubber tree (Hevea brasiliensis) (from Tree)
Image 21Share of forest area in total land area, top countries (2021) (from Forest)
Image 22European larch (Larix decidua), a coniferous tree which is also deciduous (from Tree)
Image 23Latvian Pine Forest in Ķegums Municipality (from Forest)
Image 24People trees, by Pooktre (from Tree)
Image 25Spiny forest at Ifaty, Madagascar, featuring various Adansonia (baobab) species, Alluaudia procera (Madagascar ocotillo) and other vegetation (from Forest)
Image 26Proportion of forest in protected areas, by region, 2020 (from Forest)
Image 27Tall herbaceous monocotyledonous plants such as banana lack secondary growth, but are trees under the broadest definition. (from Tree)
Image 28Dormant Magnolia bud (from Tree)
Image 29Cracked thorny skin of a Aesculus tree seed (from Tree)
Image 30Buds, leaves, flowers and fruit of oak (Quercus robur) (from Tree)
Image 31Forest in the Scottish Highlands (from Forest)
Image 32Since the 13th century, the Niepołomice Forest in Poland has had special use and protection. In this view from space, different coloration can indicate different functions. (from Forest)
Image 33A young red pine (Pinus resinosa) with spread of roots visible, as a result of soil erosion (from Tree)
Image 34Northern beech (Fagus sylvatica) trunk in autumn (from Tree)
Image 35Neem tree at Sant Nenuram Ashram (from Trees of Pakistan)
Image 36Form, leaves and reproductive structures of queen sago (Cycas circinalis) (from Tree)
Image 37Even, dense old-growth stand of beech trees (Fagus sylvatica) prepared to be regenerated by their saplings in the understory, in the Brussels part of the Sonian Forest. (from Forest)
Image 38The Daintree Rainforest (from Tree)
Image 39Sugar maple (Acer saccharum) tapped to collect sap for maple syrup (from Tree)
Image 40Broadleaf forest in Bhutan (from Forest)
Image 41Buds, leaves and reproductive structures of white fir (Abies alba) (from Tree)
Image 42Trees in art: Weeping Willow, Claude Monet, 1918 (from Tree)
Image 43Priest River winding through Whitetail Butte with lots of forestry to the east—these lot patterns have existed since the mid-19th century. The white patches reflect areas with younger, smaller trees, where winter snow cover shows up brightly to the astronauts. Dark green-brown squares are parcels (from Forest)
Image 44Alleé of London plane trees (Platanus × acerifolia) in garden (from Tree)
Image 45Burned forest on Thasos (from Forest)
Image 46Olive trees in Pakistan (from Trees of Pakistan)
Image 47Redwood tree in northern California redwood forest, where many redwood trees are managed for preservation and longevity, rather than being harvested for wood production (from Forest)
Image 48Palms and cycads as they might have appeared in the middle Tertiary (from Tree)
Image 49Selling firewood at a market (from Tree)
Image 50Lepidodendron, an extinct lycophyte tree (from Tree)
Image 51Yggdrasil, the World Ash of Norse mythology (from Tree)
Image 52Recently stripped cork oak (Quercus suber) (from Tree)
Image 534000 years old Cypress of Abarqu is the oldest tree in Iran and the second oldest tree in the world. (from List of trees of Iran)
Image 54Diagram 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. (from Tree)