Editing Acorn (section)

{{short description|Nut of the oak tree}}
{{about|the nut|the squash|Acorn squash|other uses|Acorn (disambiguation)}}
{{Use dmy dates|date=October 2021}}
[[File:Quercus robur acorn - Keila.jpg|thumb|[[English oak]] acorn]]
[[File:Acorns small to large.jpg|thumb|Acorns of the willow oak in [[South Carolina]] (from small to large, counterclockwise from center): ''[[Quercus phellos|Q.&nbsp;phellos]]'' (willow oak), ''[[Quercus falcata|Q.&nbsp;falcata]]'' (southern red oak; top right), ''[[Quercus alba|Q.&nbsp;alba]]'' (white oak), and ''[[Quercus coccinea|Q.&nbsp;coccinea]]'' (scarlet oak). Scale bar at upper right is 1&nbsp;cm.]]

[[File:Acorn diagram.jpg|thumb|Diagram of the anatomy of an acorn: A.) [[Calybium and cupule|Cupule]] B.) [[Pericarp]] (fruit wall) C.) Seed coat ([[Testa (botany)|testa]]) D.) [[Cotyledons]] (2) E.) [[Plumule]] F.) [[Radicle]] G.) Remains of [[Gynoecium|style]]. Together D., E., and F. make up the embryo.]]

The '''acorn''' is the [[nut (fruit)|nut]] of the [[oak]]s and their close relatives (genera ''[[Quercus]]'', ''[[Notholithocarpus]]'' and ''[[Lithocarpus]]'', in the family [[Fagaceae]]). It usually contains a [[seedling]] surrounded by two [[cotyledon]]s (seedling leaves), enclosed in a tough [[Nutshell|shell]] known as the pericarp, and borne in a cup-shaped [[Calybium|cupule]].<ref>{{cite book |url=https://books.google.com/books?id=WYPfQo9lUzoC&pg=PA32 |page=32 |year=2009 |title=Hands-On Chemical Ecology:: Simple Field and Laboratory Exercises |author=Dietland Müller-Schwarze |publisher=Springer Science & Business Media|isbn=978-1-4419-0378-5 }}</ref><ref>{{Cite encyclopedia |title=Acorn {{!}} Definition & Facts |author= |encyclopedia=Encyclopedia Britannica |date= |access-date=28 April 2024 |url= https://www.britannica.com/science/acorn-nut}}</ref> Acorns are {{convert|1–6|cm|in|frac=2|abbr=on}} long and {{convert|0.8–4|cm|in|frac=8|abbr=on}} on the fat side. Acorns take between 5 and 24 months (depending on the species) to mature; see the [[List of Quercus species|list of ''Quercus'' species]] for details of oak classification, in which acorn [[morphology (biology)|morphology]] and [[phenology]] are important factors.