View source for Quercus macrocarpa

{{Short description|Species of oak tree}}
{{Redirect|Burr oak|places named after the oak|Burr Oak (disambiguation){{!}}Burr Oak}}
{{Use dmy dates|date=September 2020}}
{{Speciesbox
|image=Big Tree with spring picnic.jpg
|image_caption=A 400-year old tree in [[Missouri]] known as [[The Big Tree]]
|status=LC
|status_system=IUCN3.1
|status_ref=<ref name=iucn>{{cite iucn|author1=Kenny, L. |author2=Wenzell, K. |title=Quercus macrocarpa |volume=2015 |page=e.T33991A2839807 |year=2015 |doi=10.2305/IUCN.UK.2015-4.RLTS.T33991A2839807.en }}</ref>
|genus=Quercus
|display_parents=2
|parent=Quercus sect. Quercus
|species=macrocarpa
|authority=[[André Michaux|Michx.]]
|range_map=Quercus macrocarpa range map 1.png
|range_map_caption=Generalized natural range
|synonyms_ref=<ref>{{ThePlantList |authority=Michx.}}</ref>
|synonyms={{collapsible list|bullets=true
 |''Quercus macrocarpus'' <small>Michx.</small>
 |''Cerris macrocarpa'' <small>(Michx.) Raf.</small>
 |''Cerris oliviformis'' <small>(F.Michx.) Raf.</small>
 |''Quercus macrocarpa'' var. ''abbreviata'' <small>A.DC.</small>
 |''Quercus macrocarpa'' var. ''alata'' <small>Coleman</small>
 |''Quercus macrocarpa'' f. ''appressa'' <small>Trel.</small>
 |''Quercus macrocarpa'' var. ''minor'' <small>A.DC.</small>
 |''Quercus macrocarpa'' f. ''olivaeformis'' <small>(F. Michx.) A. Gray</small>
 |''Quercus macrocarpa'' f. ''oliviformis'' <small>(F.Michx.) Trel.</small>
 |''Quercus macrocarpa'' var. ''oliviformis'' <small>(F.Michx.) A.Gray</small>
 |''Quercus macrocarpa'' subsp. ''oliviformis'' <small>(F.Michx.) A.Camus</small>
 |''Quercus macrocarpa'' f. ''orbiculata'' <small>Trel.</small>
 |''Quercus oliviformis'' <small>F.Michx.</small>
 |''Quercus olivaeformis'' <small>F.Michx.</small>
 |''Quercus macrocarpa'' subsp. ''eumacrocarpa'' <small>(Michx.) A. Camus</small>
 }}
}}

'''''Quercus macrocarpa''''', the '''bur oak''' or '''burr oak''', is a species of [[oak]] tree native to eastern North America. It is in the [[white oak]] section, ''Quercus'' sect. ''Quercus'', and is also called '''mossycup oak''', '''mossycup white oak''', '''blue oak''', or '''scrub oak'''. The acorns are the largest of any North American oak (thus the species name ''macrocarpa'', from [[Ancient Greek]] {{wikt-lang|grc|μακρός}} {{grc-tr|μακρός}} "large" and {{wikt-lang|grc|καρπός}} {{grc-tr|καρπός}} "fruit"), and are important food for wildlife.

==Description==
''Quercus macrocarpa'' is a large [[deciduous]] [[tree]] growing up to {{convert|30|m|abbr=off}}, rarely {{cvt|50|m}}, in height,<ref name="FNA">{{eFloras|1|233501058|Quercus macrocarpa |family=Fagaceae|first=Kevin C. |last=Nixon}}</ref> and is one of the most massive oaks with a trunk diameter of up to {{cvt|10|ft|0|order=flip}}. It is one of the slowest-growing oaks, with a growth rate of {{convert|12|in|cm|0|order=flip}} per year when young. However, one source states that a well-established tree can grow up to {{cvt|20|in|cm|order=flip}} per year.<ref name="Houser 2013">{{cite web |last1=Houser |first1=Steve |title=Tree Species Profiles: Top Rated Shade Trees, Bur Oak (Quercus macrocarpa) |url=https://www.arborilogical.com/articles/all-articles/article-repository/2013/april/tree-species-profiles-top-rated-shade-trees-bur-oak-quercus-macrocarpa/ |publisher=Arborilogical Services, Inc. |location=Wylie, Texas |date=19 April 2013}}</ref>{{Unreliable source?|date=December 2022}} A 20-year-old tree will be about {{cvt|60|ft|m|0|order=flip}} tall if grown in full sun.{{citation needed|date=August 2021}} Naturally occurring saplings in forests will typically be older. Bur oaks commonly live to be 200 to 300 years old, and may live up to 400 years.<ref>{{cite web |title=Quercus macrocarpa |url=http://www.ldeo.columbia.edu/~adk/oldlisteast/Spp/QUMAC.html |website=Eastern OLDLIST |year=2010 |publisher=Rocky Mountain Tree-Ring Research, Inc. and Eastern Kentucky University}}</ref> The [[Bark (botany)|bark]] is gray with distinct vertical ridges.<ref name="FNA" />

The [[leaves]] are {{cvt|7|–|15|cm|in|frac=4}} long and {{cvt|5|–|13|cm|in|frac=4}} broad, variable in shape, with a lobed margin. Most often, the basal two-thirds is narrower and deeply lobed, while the apical third is wider and has shallow lobes or large teeth. They usually do not show strong fall color, although fine golden hues are occasionally seen.{{r|Houser 2013}} The [[flower]]s are greenish-yellow [[catkin]]s, produced in the spring. The [[acorn]]s are very large, {{cvt|2.5|–|5|cm|in|frac=4}} long and {{cvt|2|-|4|cm|in|frac=4}} broad, having a large cup that wraps much of the way around the nut, with large overlapping scales and often a fringe at the edge of the cup.<ref name="FNA" />

The wood when sawn transversely shows the characteristic annual rings formed by [[Secondary growth|secondary thickening]].

Bur oak is sometimes confused with other members of the white oak section, such as ''[[Quercus bicolor]]'' (swamp white oak),{{r|gobot}} ''[[Quercus lyrata]]'' (overcup oak), and ''[[Quercus alba]]'' (white oak). It [[Hybrid (biology)|hybridises]] with several other species of oaks.

{{Gallery
|Bur Oak Winter Form.jpg|Spreading branches
|Quercus macrocarpa USDA.jpg|Leaves and acorn
|Quercus macrocarpa-Acorn R 51 g edit (24212435556).jpg|Acorns
|QuercusMacrocarpa.jpg|Bark
}}

== Varieties ==
Two [[variety (botany)|varieties]] are accepted in [[Kew]]'s [[Plants of the World Online]]:{{r|powo}}
*''Quercus macrocarpa'' var. ''macrocarpa''
*''Quercus macrocarpa'' var. ''depressa'' {{small|(Nutt.) Engelm.}}

== Distribution and habitat ==
[[File:Bur-oak-savanna.jpg|thumb|A bur oak savanna in Wisconsin hill country (the [[Driftless Area]]) in winter]]

''Quercus macrocarpa'' is widespread in the Atlantic coastal plain from [[New Brunswick]] to [[North Carolina]], west as far as [[Alberta]], eastern [[Montana]], [[Wyoming]], and northeastern [[New Mexico]]. The vast majority of the populations are found in the eastern [[Great Plains]], the [[Mississippi Valley|Mississippi]]&ndash;[[Missouri River Valley|Missouri]]&ndash;[[Ohio Valley]], and the [[Great Lakes region]].{{r|bonap}}

Bur oaks primarily grow in a [[temperate climate]] on the western [[oak–hickory forest]]ed regions in the United States and into Canada.<ref>{{cite web |last=Ward |first=James |title=Temperate Deciduous Forest Biome |website=Temperate Deciduous Forest Biome |date=2 June 2005 |url=https://dendro.cnre.vt.edu/Forsite/tdfbiome.htm}}</ref> It commonly grows in the open, away from dense [[forest]] canopy. For this reason, it is an important tree on the eastern [[prairie]]s, often found near [[waterway]]s in otherwise more forested areas, where there is a break in the canopy. It is [[drought resistant]], possibly because of its long [[taproot]]. At the end of the growing season, a one-year sapling may have a taproot {{cvt|1.37|m|ft|0|frac=2}} deep and a lateral root spread of {{cvt|76|cm|ft|0|frac=2}}.{{r|silvics}} The [[West Virginia]] state champion bur oak has a trunk diameter of almost {{cvt|3|m|ft|0}}.

Large bur oaks, older than 12 years,<ref name="FEIS">{{FEIS |genus=Quercus |species=macrocarpa |type=tree |last=Gucker |first=Corey L. |date=2011}}</ref> are fire-tolerant because of their thick bark.{{r|silvics}} One of the bur oak's most common habitats, especially in Midwestern United States, is the [[oak savanna]], where fires often occurred in early spring or late fall. Without fires, bur oak is often succeeded by other tree and shrub species that are more shade-tolerant. Older bur oaks may survive in dense woodlands for 80 years, until they are weakened by wood-rot fungi in the lower branches killed by shade, and by 100 to 110 years, they are often snapped by wind storms.<ref name="FEIS" />

==Ecology==
[[File:Andricus dimorphus galls on Bur Oak leaf.jpg|thumb|''[[Andricus dimorphus]]'' gall]]

The acorns are the largest of any North American oak{{r|silvics}} and are an important [[wildlife]] food; [[American black bear]]s sometimes tear off branches to get them. However, heavy nut crops are borne only every few years. In this evolutionary strategy, known as [[masting]], the large seed crop every few years overwhelms the ability of seed predators to eat the acorns, thus ensuring the survival of some seeds. Other wildlife, such as [[deer]] and [[porcupine]], eat the leaves, twigs and bark. [[Cattle]] are heavy browsers in some areas. The bur oak is the only known host plant of ''[[Bucculatrix recognita]]'' [[caterpillar]]s.

Many species of arthropods form [[gall]]s on the leaves and twigs, including ''[[Aceria querci]]'' (a [[mite]]) and numerous [[Cynipidae|cynipid wasps]]:  ''[[Acraspis macrocarpae]]'', ''[[Acraspis villosa]]'', ''[[Andricus chinquapin]]'', ''[[Andricus dimorphus]]'', ''[[Andricus foliaformis]]'', ''[[Andricus flavohirtus]]'', ''[[Andricus quercuspetiolicola]]'', ''[[Callirhytis flavipes]]'', ''[[Disholcaspis quercusmamma]]'', ''[[Neuroterus floccosus]]'', ''[[Neuroterus saltarius]]'', ''[[Neuroterus umbilicatus]]'', ''[[Philonix nigra]]'', and ''[[Phylloteras poculum]]''.{{r|fotcr2017}}

===Diseases===
[[Bur oak blight]] is caused by a fungal pathogen ''[[Tubakia iowensis]]''.{{r|mor}} It forms black pustules on the petioles and causes leaf discoloration and death, making the tree more susceptible to other secondary issues such as [[Armillaria root rot|''Armillaria'' root rot]] or ''[[Agrilus bilineatus]]'' (two-lined chestnut borer).{{r|mor}}

==Cultivation==
''Quercus macrocarpa'' is cultivated by [[plant nursery|plant nurseries]] for use in gardens, in parks, and on urban sidewalks. Among the white oaks, it is one of the most tolerant of [[urban area|urban]] conditions, and is one of the fastest-growing of the group.{{citation needed|date=March 2021}} It has been planted in many climates, ranging northwards to [[Anchorage, Alaska|Anchorage]], [[Alaska]], and as far south as [[Mission, Texas]].{{citation needed|date=March 2021}} It withstands [[chinook wind|chinook]] conditions in [[Calgary]], [[Alberta]].{{citation needed|date=May 2019}} It is drought tolerant.{{r|gobot}}

[[Coppicing]] has been shown to produce superior growth.<ref>Bur oak (''Quercus macrocarpa'') biomass production on a former coal mine site: positive effects of coppicing on rapid recovery of growth and yield. Canadian Journal of Forest Research 2019 49(9): 1060-1068 Mosseler, A.; Major, J.E.; and McPhee, D.</ref>

==Uses==
[[File:Bur Oak Tree Oak.jpg|thumb|Wood showing growth rings]]
The wood of ''Quercus macrocarpa'' is commercially valuable; it is durable, used for flooring, fence posts, cabinets, and barrels.{{r|silvics|ilmus}} The acorns can be eaten boiled and raw.{{r|nesom}} Native Americans have used the astringent bark to treat wounds, sores, rashes, and diarrhea.{{r|ilmus|nesom}}	

==Culture==
Many places are named after the burr oak, such as [[Burr Oak State Park]] in [[Ohio]], the cities of [[Burr Oak, Iowa]] and [[Burr Oak, Kansas]], and the village of [[Burr Oak, Michigan]]. ''Burr Oaks'' (1947) is a volume of poetry by [[Richard Eberhart]].<ref>{{cite web|title=Richard Eberhart|url=https://www.poetryfoundation.org/poems-and-poets/poets/detail/richard-eberhart|website=Poetry Foundation|access-date=2 February 2017|location=Bibliography|quote=Burr Oaks, Oxford University Press (New York, NY), 1947.}}</ref>

==References==
{{Reflist|refs=
<ref name=bonap>{{BONAP|ref |genus=Quercus |species=macrocarpa}}</ref>
<ref name=fotcr2017>{{cite book |last1=Wilhelm |first1=Gerould |author-link1=Gerould Wilhelm |last2=Rericha |first2=Laura |author-link2=Laura Rericha |date=2017 |title=Flora of the Chicago Region: A Floristic and Ecological Synthesis |publisher=Indiana Academy of Sciences}}</ref>
<ref name=gobot>{{Go Botany|genus=Quercus|species=macrocarpa|access-date=6 March 2021}}</ref>
<ref name=ilmus>{{cite web |title=Quercus macrocarpa |url=http://www.museum.state.il.us/muslink/forest/htmls/trees/Q-macrocarpa.html |website=www.museum.state.il.us |access-date=6 March 2021}}</ref>
<ref name=mor>{{cite web |title=Bur oak blight |url=https://www.mortonarb.org/trees-plants/tree-and-plant-advice/help-diseases/bur-oak-blight |website=www.mortonarb.org |publisher=The Morton Arboretum |access-date=6 March 2021}}</ref>
<ref name=nesom>{{cite web |last1=Nesom |first1=Guy |title=''Quercus macrocarpa'' |url=https://plants.usda.gov/plantguide/pdf/pg_quma2.pdf |publisher=NRCS Plant Guide |access-date=6 March 2021}}</ref>
<ref name=powo>{{cite web |title=''Quercus macrocarpa'' Michx. |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:30014114-2 |website=Plants of the World Online |publisher=[[Royal Botanic Gardens, Kew]] |access-date=6 March 2021}}</ref>
<ref name=silvics>{{Silvics |genus=Quercus |species=macrocarpa |volume=2 |first=Paul S. |last=Johnson}}</ref>
}}

==Further reading==
* {{cite web |last1=Schader |first1=Meg |title=How to Plant Bur Oak Trees |url=http://homeguides.sfgate.com/plant-bur-oak-trees-40112.html |website=SFGate |department=Home Guides |date=13 November 2020}}

==External links==
{{commonscat|Quercus macrocarpa}}

{{Taxonbar|from=Q1082365}}

[[Category:Quercus|macrocarpa]]
[[Category:Trees of Northern America]]
[[Category:Taxa named by André Michaux]]
[[Category:Plants described in 1801]]
[[Category:Plants used in traditional Native American medicine]]