A large, perennial plant with a single, woody, self-supporting stem (the trunk or bole) extending to a considerable height above the ground before branching to form the leafy crown. Trees exhibit a wide variety of shapes, from very narrow, columnar forms to wide-spreading ones, and may be evergreen or deciduous. They occur in many different plant families. Dicotyledonous and gymnosperm trees grow in height by extension of the shoots, and in girth by the addition of internal tissue layers; monocotyledonous trees achieve their full girth as seedlings, and subsequently increase in height only. A few other groups, such as the so-called tree-ferns, produce arborescent or tree-like forms.
A few species of trees grow to 100 m (328 ft) tall and some can live for several thousand years. Trees also play an intimate role in many of the world's mythologies (see trees in mythology).The earliest trees were tree ferns and horsetails, which grew in vast forests in the Carboniferous Period; Most species of trees today are flowering plants and conifers.
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.
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 modern trees (all conifers, and all broadleaf trees), grow by the addition of new wood outwards, immediately under the bark. 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; Above ground, the trunk gives height to the leaf-bearing branches, aiding in competition with other plant species for sunlight. 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. 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. Bamboos by contrast, do show most of the characteristics of trees, yet are rarely called trees.
Champion trees
The world's champion trees can be considered on several factors; It is significant that in each case, the top position is always held by a conifer, though a different species in each case;
Tallest treesThe 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. The following are now accepted as the top five tallest reliably measured species:
Coast Redwood Sequoia sempervirens: 115.55 m (378.1 ft.), Redwood National Park, California (Gymnosperm Database) Coast Douglas-fir Pseudotsuga menziesii: 100.3
m (329.1 ft.), Brummit Creek, Coos County, Oregon (Gymnosperm Database) Sitka Spruce Picea sitchensis: 96.7 m (317.3 ft.), Prairie Creek Redwoods State Park,
California (Gymnosperm Database) Giant Sequoia Sequoiadendron giganteum: 93.6 m (307.1 ft.), Redwood Mountain Grove, California (Gymnosperm Database) Australian Mountain-ash
Eucalyptus regnans: 92.0 m (301.8 ft.), Styx Valley, Tasmania (Forestry Tasmania [pdf file]; also reported, less verifiably, as 97.0 m Tasmanian Giant Trees) Stoutest trees
The girth (circumference) of a tree is – or at least should be – 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 the British Isles:
"The aberrations of past measurements of yews are beyond belief. this is defined differently in different situations, with most foresters measuring girth at 1.3 m above ground, while ornamental tree measurers usually measure at 1.5 m above ground;The stoutest species in diameter, excluding baobabs, are:
Montezuma Cypress Taxodium mucronatum: 11.42 m, Árbol del Tule, Santa Maria del Tule, Oaxaca, Mexico (A. Giant Sequoia Sequoiadendron giganteum: 8.85 m, General Grant tree, Grant Grove, California (Gymnosperm Database) Coast Redwood Sequoia sempervirens: 7.44 m, Prairie Creek Redwoods State Park, California (Gymnosperm Database) Largest treesThe 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.
The top four species measured so far are (Gymnosperm Database):
Giant Sequoia Sequoiadendron giganteum: 1489 m³, General Sherman Coast Redwood Sequoia sempervirens: 1045 m³, Del Norte Titan tree Western Redcedar Thuja plicata: 500 m³, Quinault Lake Redcedar Kauri Agathis australis: 400 m³, Tane Mahuta tree (total volume, including branches, 516.7 m³)However, the Alerce Fitzroya cupressoides, as yet un-measured, may well slot in at third or fourth place, and Montezuma Cypress Taxodium mucronatum is also likely to be high in the list.
Oldest treesThe 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 centre of the tree. It is also only possible for trees which are solid to the centre of the tree; 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.
The verified oldest measured ages are (Gymnosperm Database):
Great Basin Bristlecone Pine Pinus longaeva: 4844 years Alerce Fitzroya cupressoides: 3622 years Giant Sequoia Sequoiadendron giganteum: 3266 years Huon-pine Lagarostrobos franklinii: 2500 years Rocky Mountains Bristlecone Pine Pinus aristata: 2435 yearsOther species suspected of reaching exceptional age include European Yew Taxus baccata (probably over 3000 years) and Western Redcedar Thuja plicata. broadleaf or hardwood trees) 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 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 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 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 Stuartia, Stuartia 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; 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 speciesGinkgos (Ginkgophyta)
Ginkgoaceae (Ginkgo family) Ginkgo, Ginkgo bilobaCycads (Cycadophyta)
Cycadaceae family Ngathu cycad, Cycas angulata Zamiaceae family Wunu cycad, Lepidozamia hopeiFerns (Pterophyta)
Cyatheaceae and Dicksoniaceae families Tree ferns, Cyathea, Alsophila, Dicksonia (not a monophyletic group)Life stages
The life cycles of trees, especially conifers, are divided into the following stages in forestry for survey and documentation purposes, though the boundaries between stages vary among foresters:
Seed Seedling: the above-ground part of the embryo that sprouts from the seed Sapling: After the seedling reaches 1 m tall, and until it reaches 7 cm in stem diameter Pole: young trees from 7–30 cm diameter Mature tree: over 30 cm diameter, reproductive years begin Old tree: dominate old growth forest; height growth slows greatly, with majority of productivity in seed production Overmature: dieback and decay become common Snag: standing dead wood Log/debris: fallen dead woodTree diameters are measured at height of between 1.3–1.5 m above the highest point on the ground at its base (known as "breast height").
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