View source for Oak

{{Taxobox
| name = Oak (''Quercus'')
| image = Quercus robur.jpg
| image_width = 240px
| image_caption = Foliage and acorns of ''[[Pedunculate oak|Quercus robur]]''
| regnum = [[Plant]]ae
| phylum = [[flowering plant|Magnoliophyta]]
| classis = [[dicotyledon|Magnoliopsida]]
| ordo = [[Fagales]]
| familia = [[Fagaceae]]
| genus = '''''Quercus'''''
| genus_authority = [[Carolus Linnaeus|L.]]
}}
[[File:1500 year old Oak Tree (2308284491).jpg|thumb|250px|An old oak tree]]

The '''oak tree''' is a [[tree]] or [[shrub]] in the [[genus]] '''''Quercus'''''. There are about 500 living [[species]]. They are divided into [[subgenus|subgenera]]. The common name "oak" may also appear in the names of species in related genera, such as ''[[Lithocarpus]]''.<ref>Hogan, C. Michael 2012. [http://www.eoearth.org/article/Oak ''Oak'']. ed. Arthur Dawson. Encyclopedia of Earth. National Council for Science and the Environment. Washington DC</ref>

Oaks have [[spiral]]ly arranged [[leaf|leaves]], with rounded edges in many species; some have leaves with jagged edges or entire leaves with smooth margins. Many deciduous species do not drop dead leaves until the next Spring. In [[spring (season)|Spring]], a single oak tree produces both male flowers (as [[catkin]]s) and small female flowers.<ref>Conrad, Jim. 2011. [http://www.backyardnature.net/fl_bloak.htm "Oak flowers"]. backyardnature.com.</ref> The [[fruit]] is a [[nut (fruit)|nut]] called an [[acorn]], carried in a cup-like structure. Each acorn has one seed (rarely two or three) and takes 6–18 months to mature, depending on species. The so-called "live oaks" are [[evergreen]]. They are not a [[taxonomy|taxonomic group]], just a [[life style]] which occurs in the genus.

The oak is a kind of [[hardwood]] [[forest]] tree. They are well known as a [[climax vegetation]] in the [[temperate zone]] of the [[northern hemisphere]]. That means, left untouched by humans, it would be the dominant tree. Much of England was covered by oak forests before modern [[farming]] took over the land. The last extensive oak [[woodland]]s were cut down to build ships for the [[Royal Navy]] in the 18th century.

Some kinds of oak [[wood]] are very hard. That is why people in past centuries cut them down to make ships, [[furniture]] and other things. The wood is now scarce and expensive and only used to make a few things anymore. Much cheaper are [[softwood]]s like [[pine]].

Oak trees grow slowly and can live up to 1000 years.

== Associated animals ==
A mature oak tree stands about 100 feet tall (~30 metres). It is a home for more animals than any other European tree.<ref name=Dickie>Attenborough, David 1995. ''The private life of plants''. London: BBC Books, 152{{ndash}}158. {{ISBN|0-563-37023-8}}</ref> 30 species of birds, 45 different [[Hemiptera|bugs]] and over 200 species of [[moth]] have been found on oaks. [[Beetles]] burrow under the bark, and some drill holes into the wood. The leaves are eaten by many [[caterpillars]]. Many leaves carry strange little bumps on the underside. These are insect [[gall]]s, caused by many little animals. [[Midge]]s, moths, [[worms]] and tiny [[wasps]] lay their eggs in leaves or leaf [[wikt:bud|buds]]. The leaf reacts by forming a growth around the eggs. Inside the gall, larvae develop. The leaf falls, but the larvae may come out only the next [[Spring (season)|spring]]. Small galls only have one larva, but larger galls may contain as many as 30 larvae.<ref name=Dickie />

== Acorns ==
{{Main|Acorn}}

Oak trees produce acorns once a year which ripen in [[autumn]]. Oak trees may start producing acorns when they are about 20 years old. A mature oak may produce 90,000 acorns a year; this is several millions in its lifetime.<ref name=Dickie />

== Related pages ==
* [[Cork oak]]

== References ==
{{wikispecies|Quercus}}
{{reflist}}

{{Taxonbar|from=Q12004}}
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[[Category:Trees]]
[[Category:Fagales]]