• Finnish: puu
• German: Baum, Baum
• Japanese: 木 (ki)
• Lithuanian: medis
• Novial: arbre
• Swedish: träd

• Finnish: puu
• German: Baum, Baum
• Japanese: ツリー構造 (tsurī-kōzo)
• Lithuanian: medis
• Novial: arbre
• Swedish: träd

Verb

1. To chase (an animal or person) up a tree.

   The dog treed the cat.

Translations

• Finnish: ajaa puuhun
• Hebrew: עץ
• Hungarian: fa

Dutch

Noun

tree (contraction of trede)

1. step (of a staircase), stair

A tree is a perennial woody plant. It is most often defined as a woody plant that has secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to 6 m; some authors set a minimum of 10 cm trunk diameter (30 cm girth). Woody plants that do not meet these definitions by having multiple stems and/or small size, are called shrubs. Compared with most other plants, trees are long-lived, some of them getting to be several thousand years old and growing to up to 115 m (375 ft) high.

Trees are an important component of the natural landscape because of their prevention of erosion and the provision of a specific weather-sheltered ecosystem in and under their foliage. Trees have also been found to play an important role in producing oxygen and reducing carbon dioxide in the atmosphere, as well as moderating ground temperatures. They are also significant elements in landscaping and agriculture, both for their aesthetic appeal and their orchard crops (such as apples). Wood from trees is a common building material. Trees also play an intimate role in many of the world's mythologies (see trees in mythology).

Classification

A tree is a plant form that occurs in many different orders and families of plants. Trees show a wide variety of growth forms, leaf type and shape, bark characteristics, and reproductive organs.

The tree form has evolved separately in unrelated classes of plants, in response to similar environmental challenges, making it a classic example of parallel evolution.

The earliest trees were tree ferns and horsetails, which grew in vast forests in the Carboniferous Period; tree ferns still survive, but the only surviving horsetails are not of tree form. Later, in the Triassic Period, conifers, ginkgos, cycads and other gymnosperms appeared, and subsequently flowering plants in the Cretaceous Period. Most species of trees today are flowering plants (Angiosperms) and conifers. The listing below gives examples of many well-known trees and how they are typically classified.

A small group of trees growing together is called a grove or copse, and a landscape covered by a dense growth of trees is called a forest. Several biotopes are defined largely by the trees that inhabit them; examples are rainforest and taiga (see ecozones). A landscape of trees scattered or spaced across grassland (usually grazed or burned over periodically) is called a savanna. A forest of great age is called old growth forest or ancient woodland (in the UK). A young tree is called a sapling.

Morphology

The basic parts of a tree are the roots, trunk(s), branches, twigs and leaves. Tree stems consist mainly of support and transport tissues (xylem and phloem). Wood consists of xylem cells, and bark is made of phloem and other tissues external to the vascular cambium. Trees may be broadly grouped into exogenous and endogenous trees according to the way in which their stem diameter increases. Exogenous trees, which comprise the great majority of trees (all conifers, and almost all broadleaf trees), grow by the addition of new wood outwards, immediately under the bark. Endogenous trees, mainly in the monocotyledons (e.g., palms and dragon trees), but also cacti, grow by addition of new material inwards.

As an exogenous tree grows, it creates growth rings as new wood is laid down concentrically over the old wood. In species growing in areas with seasonal climate changes, wood growth produced at different times of the year may be visible as alternating light and dark, or soft and hard, rings of wood. In tropical rainforest regions with constant year-round climate, growth is continuous and the growth rings are not visible with no change in the wood texture. In species with annual rings, these rings can be counted to determine the age of the tree, and used to date cores or even wood taken from trees in the past, a practice is known as the science of dendrochronology. Very few tropical trees can be accurately aged in this manner. Age determination is also impossible in endogenous trees.

The roots of a tree are generally embedded in earth, providing anchorage for the above-ground biomass and absorbing water and nutrients from the soil. It should be noted, however, that while ground nutrients are essential to a tree's growth the majority of its biomass comes from carbon dioxide absorbed from the atmosphere (see photosynthesis). Above ground, the trunk gives height to the leaf-bearing branches, aiding in competition with other plant species for sunlight. In many trees, the arrangement of the branches optimizes exposure of the leaves to sunlight.

Not all trees have all the plant organs or parts mentioned above. For example, most palm trees are not branched, the saguaro cactus of North America has no functional leaves, tree ferns do not produce bark, etc. Based on their general shape and size, all of these are nonetheless generally regarded as trees. Sometimes size is the most important consideration. A plant form that is similar to a tree, but generally having smaller, multiple trunks and/or branches that arise near the ground, is called a shrub. However, no precise differentiation between shrubs and trees is possible. Given their small size, bonsai plants would not technically be 'trees', but one should not confuse reference to the form of a species with the size or shape of individual specimens. A spruce seedling does not fit the definition of a tree, but all spruces are trees.

Record breaking trees

The world's champion trees can be considered on several factors; height, trunk diameter or girth, total size, and age. It is significant that in each case, the top position is always held by a conifer, though a different species in each case; in most measures, the second to fourth places are also held by conifers.

Tallest trees

The heights of the tallest trees in the world have been the subject of considerable dispute and much (often wild) exaggeration. Modern verified measurement with laser rangefinders combined with tape drop measurements made by tree climbers, carried out by the U.S. Eastern Native Tree Society has shown that most older measuring methods and measurements are unreliable, often producing exaggerations of 5% to 15% above the real height. Historical claims of trees of , , and even , are now largely disregarded as unreliable, fantasy or outright fraud (however, see "Tallest specimens" chapter in Eucalyptus regnans article). The following are now accepted as the top five tallest reliably measured species:

1. Coast Redwood Sequoia sempervirens: 115.55 m (379.1 ft), Redwood National Park, California, United States
2. Coast Douglas-fir Pseudotsuga menziesii: , Brummit Creek, Coos County, Oregon, United States
3. Australian Mountain-ash Eucalyptus regnans: , Styx Valley, Tasmania, Australia
4. Sitka Spruce Picea sitchensis: , Prairie Creek Redwoods State Park, California, United States
5. Giant Sequoia Sequoiadendron giganteum: , Redwood Mountain Grove, Kings Canyon National Park, California, United States

Stoutest trees

The girth (circumference) of a tree is much easier to measure than the height, as it is a simple matter of stretching a tape round the trunk, and pulling it taut to find the circumference. Despite this, UK tree author Alan Mitchell made the following comment about measurements of yew trees in a handbook "Conifers in the British Isles":

"The aberrations of past measurements of yews are beyond belief. For example, the tree at Tisbury has a well-defined, clean, if irregular bole at least 1.5 m long. It has been found to have a girth which has dilated and shrunk in the following way: 11.28 m (1834 Loudon), 9.3 m (1892 Lowe), 10.67 m (1903 Elwes and Henry), 9.0 m (1924 E. Swanton), 9.45 m (1959 Mitchell) .... Earlier measurements have therefore been omitted."

As a general standard, tree girth is taken at 'breast height'; this is defined differently in different situations, with most forestry measurements taking girth at 1.3 m above ground, while those who measure ornamental trees usually measure at 1.5 m above ground; Note though that this diameter includes buttressing; the actual idealised diameter of the area of its wood is .

1. Coast Redwood Sequoia sempervirens: , Prairie Creek Redwoods State Park, California, United States.

Charles Darwin reported finding Fitzroya cupressoides with trunk circumferences of up to 40 m (130 ft) implying a diameter of about 12 m (40 ft), but this may be an anomaly as the largest known measurements are about 5 m.

An addition problem lies in cases where multiple trunks (whether from an individual tree or multiple trees) grow together. The Sacred Fig is a notable example of this, forming additional 'trunks' by growing adventitious roots down from the branches, which then thicken up when the root reaches the ground to form new trunks; a single Sacred Fig tree can have hundreds of such trunks.

Largest trees

The largest trees in total volume are those which are both tall and of large diameter, and in particular, which hold a large diameter high up the trunk. Measurement is very complex, particularly if branch volume is to be included as well as the trunk volume, so measurements have only been made for a small number of trees, and generally only for the trunk. No attempt has ever been made to include root volume. Measuring standards vary (for example, Del Norte Titan below, is listed as the largest coastal redwood, but the Lost Monarch in Jedediah Smith Redwoods State Park is even larger at over 42,000 cubic feet).

The top four species measured so far are:

1. Giant Sequoia Sequoiadendron giganteum: 1,489 m³ (55,040 cu ft), General Sherman

Oldest trees

The oldest trees are determined by growth rings, which can be seen if the tree is cut down or in cores taken from the edge to the center of the tree. Accurate determination is only possible for trees which produce growth rings, generally those which occur in seasonal climates; trees in uniform non-seasonal tropical climates grow continuously and do not have distinct growth rings. It is also only possible for trees which are solid to the center of the tree; many very old trees become hollow as the dead heartwood decays away. For some of these species, age estimates have been made on the basis of extrapolating current growth rates, but the results are usually little better than guesswork or wild speculation. White (1998) proposes a method of estimating the age of large and veteran trees in the United Kingdom through the correlation between a tree's stem diameter, growth character and age.

The verified oldest measured ages are:

1. Norway Spruce Picea abies: 9,550 years
2. Great Basin Bristlecone Pine (Methuselah) Pinus longaeva: 4,844 years
3. Alerce Fitzroya cupressoides: 3,622 years) and Western Redcedar Thuja plicata.

The oldest reported age for an angiosperm tree is 2293 years for the Sri Maha Bodhi Sacred Fig (Ficus religiosa) planted in 288 BC at Anuradhapura, Sri Lanka; this is also the oldest human-planted tree with a known planting date.

Trees in culture

The tree has been and still is a popular cultural symbol in most of the world. Common icons are the World tree, for instance Yggdrasil, and the tree of life. The tree often represents nature or the environment itself.

Major tree genera

Flowering plants (Magnoliophyta; angiosperms)

Dicotyledons (Magnoliopsida; broadleaf or hardwood trees)

• Adoxaceae (Moschatel family)
  • Moschatel, Adoxa moschatellina
  • Elderberry, Sambucus species
  • Sinadoxa, Sinadoxa corydalifolia
  • Viburnum, Viburnum species
• Altingiaceae (Sweetgum family)
  • Sweetgum, Liquidambar species
• Anacardiaceae (Cashew family)
  • Cashew, Anacardium occidentale
  • Mango, Mangifera indica ** Pistachio, Pistacia vera
  • Sumac, Rhus species
  • Lacquer tree, Toxicodendron verniciflua
• Annonaceae (Custard apple family)
  • Cherimoya Annona cherimola
  • Custard apple Annona reticulata
  • Pawpaw Asimina triloba
  • Soursop Annona muricata
• Apocynaceae (Dogbane family)
  • Pachypodium Pachypodium species
• Aquifoliaceae (Holly family)
  • Holly, Ilex species
• Araliaceae (Ivy family)
  • Kalopanax, Kalopanax pictus * Betulaceae (Birch family)
  • Alder, Alnus species
  • Birch, Betula species
  • Hornbeam, Carpinus species
  • Hazel, Corylus species
• Bignoniaceae (family)
  • Catalpa, Catalpa species
• Cactaceae (Cactus family)
  • Saguaro, Carnegiea gigantea
• Cannabaceae (Cannabis family)
  • Hackberry, Celtis species
• Cornaceae (Dogwood family)
  • Dogwood, Cornus species
• Dipterocarpaceae family
  • Garjan Dipterocarpus species
  • Sal Shorea species
• Ebenaceae (Persimmon family)
  • Persimmon, Diospyros species
• Ericaceae (Heath family)
  • Arbutus, Arbutus species
• Eucommiaceae (Eucommia family)
  • Eucommia Eucommia ulmoides
• Fabaceae (Pea family)
  • Acacia, Acacia species
  • Honey locust, Gleditsia triacanthos
  • Black locust, Robinia pseudoacacia
  • Laburnum, Laburnum species
  • Pau Brasil, Brazilwood, Caesalpinia echinata
• Fagaceae (Beech family )
  • Chestnut, Castanea species
  • Beech, Fagus species
  • Southern beech, Nothofagus species
  • Tanoak, Lithocarpus densiflorus
  • Oak, Quercus species
• Fouquieriaceae (Boojum family)
  • Boojum, Fouquieria columnaris
• Hamamelidaceae (Witch-hazel family)
  • Persian Ironwood, Parrotia persica
• Juglandaceae (Walnut family)
  • Walnut, Juglans species
  • Hickory, Carya species
  • Wingnut, Pterocarya species
• Lauraceae (Laurel family)
  • Cinnamon Cinnamomum zeylanicum
  • Bay Laurel Laurus nobilis
  • Avocado Persea americana
• Lecythidaceae (Paradise nut family)
  • Brazil Nut Bertholletia excelsa
• Lythraceae Loosestrife family
  • Crape-myrtle Lagerstroemia species
• Magnoliaceae (Magnolia family)
  • Tulip tree, Liriodendron species
  • Magnolia, Magnolia species
• Malvaceae (Mallow family; including Tiliaceae, Sterculiaceae and Bombacaceae) ** Baobab, Adansonia species
  • Silk-cotton tree, Bombax species
  • Bottletrees, Brachychiton species
  • Kapok, Ceiba pentandra
  • Durian, Durio zibethinus
  • Balsa, Ochroma lagopus
  • Cacao (cocoa), Theobroma cacao
  • Linden (Basswood, Lime), Tilia species
• Meliaceae (Mahogany family)
  • Neem, Azadirachta indica
  • Bead tree, Melia azedarach
  • Mahogany, Swietenia mahagoni
• Moraceae (Mulberry family) ** Fig, Ficus species
  • Mulberry, Morus species
• Myristicaceae (Nutmeg family)
  • Nutmeg, Mysristica fragrans
• Myrtaceae (Myrtle family)
  • Eucalyptus, Eucalyptus species
  • Myrtle, Myrtus species
  • Guava, Psidium guajava
• Nyssaceae (Tupelo family; sometimes included in Cornaceae)
  • Tupelo, Nyssa species
  • Dove tree, Davidia involucrata
• Oleaceae (Olive family) ** Olive, Olea europaea
  • Ash, Fraxinus species
• Paulowniaceae (Paulownia family)
  • Foxglove Tree, Paulownia species
• Platanaceae (Plane family)
  • Plane, Platanus species
• Rhizophoraceae (Mangrove family)
  • Red Mangrove, Rhizophora mangle
• Rosaceae (Rose family)
  • Rowans, Whitebeams, Service Trees Sorbus species
  • Hawthorn, Crataegus species
  • Pear, Pyrus species
  • Apple, Malus species
  • Almond, Prunus dulcis
  • Peach, Prunus persica
  • Apricot, Prunus armeniaca
  • Plum, Prunus domestica
  • Cherry, Prunus species
• Rubiaceae (Bedstraw family)
  • Coffee, Coffea species
• Rutaceae (Rue family)
  • Citrus, Citrus species
  • Cork-tree, Phellodendron species
  • Euodia, Tetradium species
• Salicaceae (Willow family)
  • Aspen, Populus species
  • Poplar, Populus species
  • Willow, Salix species
• Sapindaceae (including Aceraceae, Hippocastanaceae) (Soapberry family)
  • Maple, Acer species
  • Buckeye, Horse-chestnut, Aesculus species
  • Mexican Buckeye, Ungnadia speciosa
  • Lychee, Litchi sinensis
  • Golden rain tree, Koelreuteria
• Sapotaceae (Sapodilla family)
  • Argan, Argania spinosa
  • Gutta-percha, Palaquium species
  • Tambalacoque, or "dodo tree", Sideroxylon grandiflorum, previously Calvaria major
• Simaroubaceae family
  • Tree of heaven, Ailanthus species
• Theaceae (Camellia family)
  • Gordonia, Gordonia species
  • Stewartia, Stewartia species
• Thymelaeaceae (Thymelaea family)
  • Ramin, Gonystylus species
• Ulmaceae (Elm family)
  • Elm, Ulmus species
  • Zelkova, Zelkova species
• Verbenaceae family
  • Teak, Tectona species

Monocotyledons (Liliopsida)

• Agavaceae (Agave family)
  • Cabbage tree, Cordyline australis
  • Dragon tree, Dracaena draco
  • Joshua tree, Yucca brevifolia
• Arecaceae (Palmae) (Palm family)
  • Areca Nut, Areca catechu
  • Coconut Cocos nucifera
  • Date Palm, Phoenix dactylifera
  • Chusan Palm, Trachycarpus fortunei
• Poaceae (grass family)
  • Bamboos Poaceae subfamily Bambusoideae
• Note that banana 'trees' are not actually trees; they are not woody nor is the stalk perennial.

Conifers (Pinophyta; softwood trees)

• Araucariaceae (Araucaria family)
  • Araucaria, Araucaria species
  • Kauri, Agathis species
  • Wollemia, Wollemia nobilis
• Cupressaceae (Cypress family)
  • Cypress, Cupressus species
  • Cypress, Chamaecyparis species
  • Juniper, Juniperus species
  • Alerce or Patagonian cypress, Fitzroya cupressoides
  • Sugi, Cryptomeria japonica
  • Coast Redwood, Sequoia sempervirens
  • Giant Sequoia, Sequoiadendron giganteum
  • Dawn Redwood, Metasequoia glyptostroboides
  • Western Redcedar Thuja plicata
  • Bald Cypress, Taxodium species
• Pinaceae (Pine family)
  • White pine, Pinus species
  • Pinyon pine, Pinus species
  • Pine, Pinus species
  • Spruce, Picea species
  • Larch, Larix species
  • Douglas-fir, Pseudotsuga species
  • Fir, Abies species
  • Cedar, Cedrus species
• Podocarpaceae (Yellowwood family)
  • African Yellowwood, Afrocarpus falcatus
  • Totara, Podocarpus totara
  • Miro, Prumnopitys ferruginea
  • Kahikatea, Dacrycarpus dacrydioides
  • Rimu, Dacrydium cupressinum
• Sciadopityaceae,
  • Kusamaki, Sciadopitys species
• Taxaceae (Yew family)
  • Yew, Taxus species

Ginkgos (Ginkgophyta)

• Ginkgoaceae (Ginkgo family)
  • Ginkgo, Ginkgo biloba

Cycads (Cycadophyta)

• Cycadaceae (Cycad family)
  • Ngathu cycad, Cycas angulata
• Zamiaceae (Zamia family)
  • Wunu cycad, Lepidozamia hopei

Ferns (Pteridophyta)

• Cyatheaceae and Dicksoniaceae
  • Tree ferns, Cyathea, Alsophila, Dicksonia (not a monophyletic group)

Fossil trees

• Wattieza, the earliest known tree

See also

• Arboretum
• Arboriculture
• Arborsculpture
• Christmas tree
• Deforestation
• Dendrology
• Exploding tree
• Fruit trees
• List of famous trees
• Mother of the Forest
• Plantation
• Tree climbing
• Tree line
• Trees of the world
• Urban forestry
• Woodland management

References

Bibliography

• Pakenham, T. (2002). Remarkable Trees of the World. ISBN 0-297-84300-1
• Pakenham, T. (1996). Meetings with Remarkable Trees. ISBN 0-297-83255-7
• Tudge, C. (2005). The Secret Life of Trees. How They Live and Why They Matter. Allen Lane. London. ISBN 0-713-99698-6

External links

• The Arbor Day Foundation
• International Society of Arboriculture
• Global Trees Campaign (campaigning to save the world's most threatened trees)

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