American chestnut

File:Castanea dentata.JPG

File:AmericanChestnutPollen.JPGs]]

Castanea dentata is a large, rapidly-growing, deciduous hardwood eudicot tree.{{cite journal |last1=Jacobs |first1=Douglass F |last2=Severeid |first2=Larry R |title=Dominance of interplanted American chestnut (Castanea dentata) in southwestern Wisconsin, USA |journal=Forest Ecology and Management |date=April 2004 |volume=191 |issue=1–3 |pages=111–120 |doi=10.1016/j.foreco.2003.11.015|bibcode=2004ForEM.191..111J }} A singular specimen manifest in Maine has attained a height of {{convert|115|ft|m}}.{{cite web |title=Tallest American chestnut tree in North America discovered in Lovell, Maine |website=University of Maine |url=https://umaine.edu/news/blog/2015/11/25/tallest-american-chestnut-tree-in-north-america-discovered-in-lovell-maine/ |date=25 November 2015}} Pre-blight sources give a maximum height of {{convert|100|ft|m}} and a maximum circumference of {{convert|13|ft|m}}.{{cite journal |last1=Collins |first1=Rachel J. |last2=Copenheaver |first2=Carolyn A. |last3=Kester |first3=Mary E. |last4=Barker |first4=Ethan J. |last5=DeBose |first5=Kyrille Goldbeck |title=American Chestnut: Re-Examining the Historical Attributes of a Lost Tree |journal=Journal of Forestry |date=2017 |doi=10.5849/JOF-2016-014}} Post-blight sources erroneously report a greater maximum size of the species compared with pre-blight, likely the result of nostalgia, interpretations of pre-blight measurements of circumference as being measurements of diameter, and the misapprehension that pre-blight observations of maximum size represented observations of average size.{{cite web |title=In The Maine Woods, A Towering Giant Could Help Save Chestnuts |url=https://www.npr.org/sections/thesalt/2015/12/17/459203467/in-the-maine-woods-a-towering-giant-could-help-save-chesnuts |work=All Things Considered |first=Susan |last=Sharon |publisher=NPR |date=17 December 2015 |access-date=12 July 2024 |language=en}}{{cite web |title=Research explains larger-than-life perceptions of American chestnut |url=https://www.roanoke.edu/news/new_research_explains_larger-than-life_perceptions_of_american_chestnut |date=17 May 2018 |website=roanoke.edu |access-date=12 July 2024 |language=en}}{{cite journal |last1=Collins |first1=Rachel J. |last2=Copenheaver |first2=Carolyn A. |last3=Kester |first3=Mary E. |last4=Barker |first4=Ethan J. |last5=DeBose |first5=Kyrille Goldbeck |title=American Chestnut: Re-Examining the Historical Attributes of a Lost Tree |journal=Journal of Forestry |date=2017 |doi=10.5849/JOF-2016-014|doi-access=free }} It is considerably larger than the closely related Allegheny chinquapin (Castanea pumila).{{cite web |url=https://www.tacf.org/wp-content/uploads/2016/09/Spring_2010_Mast-5.pdf |page=4 |volume=12 |issue=1 |date=Spring 2010 |work=The American Chestnut Foundation |title=Chinkapins vs. chestnuts}}

There are several other chestnut species, such as the European sweet chestnut (C. sativa), Chinese chestnut (C. mollissima), and Japanese chestnut (C. crenata). Castanea dentata can be distinguished by a few morphological traits, such as petiole length, nut size and number of nuts per burr, leaf shape, and leaf size, with leaves being {{convert|14|–|20|cm|in|round=0.5|abbr=on}} long and {{convert|7|–|10|cm|in|round=0.5|abbr=on}} broad—slightly shorter and broader than the sweet chestnut.{{cite web |url=https://tacf.org/wp-content/uploads/2017/11/Chestnut-Identification-Presentation-2012.pdf |title=Chestnut Species ID: The Basics |work=The American Chestnut Foundation |access-date=12 July 2024 }} It has larger and more widely spaced saw-teeth on the edges of its leaves, as indicated by the scientific name dentata, Latin for "toothed".{{cite book |title=Biotechnology of fruit and nut crops |chapter=10 Fagaceae |pages=206 to 237 |date=2020 |publisher=CABI |location=Wallingfor, Oxfordshire, UK |isbn=978-1-78064-827-9 |edition=2nd |editor-last1=Litz |editor-first1=Richard E. |editor-last2=Pliego-Alfaro |editor-first2=Fernando |editor-last3=Hormaza |editor-first3=Jose Ignacio |first1=Scott A. |last1=Merkle |first2=Francisco Javier |last2=Viéitez |first3=Elena |last3=Correidoira |first4=John E. |last4=Carlson |chapter-url=https://books.google.com/books?id=TrvTDwAAQBAJ&pg=PA206 }}

The European sweet chestnut was introduced in the United States by Thomas Jefferson in 1773. The European sweet chestnut has hairy twig tips in contrast to the hairless twigs of the American chestnut. This species has been the chief source of commercial chestnuts in the United States. Japanese chestnut was inadvertently introduced into the United States by Thomas Hogg in 1876 and planted on the property of S. B. Parsons in Flushing, New York. The Japanese chestnut has narrow leaves, smaller than either American chestnut or sweet chestnut, with small, sharply-pointed teeth and many hairs on the underside of the leaf and is the most blight-resistant species.{{cite web |first=Sandra L. |last=Anagnostakis |title=Chestnut Importations into the US |url=https://portal.ct.gov/caes/fact-sheets/plant-pathology/chestnut-importations-into-the-us |website=CT.gov |access-date=12 July 2024 |language=en}}

The chestnut is monoecious, and usually protandrous producing many small, pale green (nearly white) male flowers found tightly occurring along 6 to 8 inch long catkins.{{cite journal |last1=Rutter |first1=Philip A. |last2=Miller |first2=G. |last3=Payne |first3=Jerry A. |title=Chestnuts (Castanea) |journal=Acta Horticulturae |date=May 1991 |issue=290 |pages=761–790 |doi=10.17660/ActaHortic.1991.290.17}} The female parts are found near the base of the catkins (near twig) and appear in late spring to early summer.{{cite journal |last1=Fernando |first1=Danilo D. |last2=Richards |first2=Javonna L. |last3=Kikkert |first3=Julie R. |title=In vitro germination and transient GFP expression of American chestnut (Castanea dentata) pollen |journal=Plant Cell Reports |date=May 2006 |volume=25 |issue=5 |pages=450–456 |doi=10.1007/s00299-005-0088-z |pmid=16341724 |bibcode=2006PCelR..25..450F |s2cid=21643641 }} Like all members of the family Fagaceae, American chestnut is self-incompatible and requires two trees for pollination,{{cite journal |last1=Westbrook |first1=Jared W. |last2=Holliday |first2=Jason A. |last3=Newhouse |first3=Andrew E. |last4=Powell |first4=William A. |title=A plan to diversify a transgenic blight-tolerant American chestnut population using citizen science |journal=Plants, People, Planet |pages=84–95 |language=en |doi=10.1002/ppp3.10061 |date=January 2020 |volume=2 |issue=1 |s2cid=199636721 |doi-access=free |bibcode=2020PlPP....2...84W }} which can be with other members of the Castanea genus.{{cite journal |last1=Fernández-López |first1=Josefa |title=Identification of the genealogy of interspecific hybrids between Castanea sativa, Castanea crenata and Castanea mollissima |journal=Forest Systems |date=1 April 2011 |volume=20 |issue=1 |page=65 |doi=10.5424/fs/2011201-9136|doi-access=free }} The pollen is considered a mild allergen.{{cite web |url=https://www.pollenlibrary.com/Local/Specie/Castanea+dentata/in/Erie%20County/OH/ |title=American Chestnut (Castanea dentata) |access-date=June 27, 2022 |archive-date=October 14, 2023 |archive-url=https://web.archive.org/web/20231014234320/https://www.pollenlibrary.com/Local/Specie/Castanea+dentata/in/Erie%20County/OH/ }}

The American chestnut is a prolific bearer of nuts, with inflorescence and nut production in the wild beginning when a tree is 8 to 10 years old.Zon, Raphael. Chestnut in southern Maryland. No. 53. pp 31. US Department of Agriculture, Bureau of Forestry, 1904. Burrs often open while still attached to the tree, around the time of the first frost in autumn, with the nuts then falling to the ground.{{cite web|url=https://www.concordmonitor.com/Chestnuts-13311536|title=Chestnuts reemerge|access-date=June 22, 2022|archive-date=January 29, 2023|archive-url=https://web.archive.org/web/20230129150025/https://www.concordmonitor.com/Chestnuts-13311536 |date=November 3, 2017 |work=Concord Monitor |first=Hillary |last=Nelson }} American chestnut typically have three nuts enclosed in a spiny, green burr, each lined in a tan velvet.{{cite web |url=https://www.tacf.org/wp-content/uploads/2016/08/MegaTIDvue.pdf|title=How to identify American chestnut trees|date=May 2008|website=Appalachian Trail Mega-Transect Chestnut Project|publisher=The American Chestnut Foundation|orig-date=Originally published May 2000 in revised first edition of Field Guide for locating, pollinating, and harvesting nuts from flowering American Chestnut Trees (Castanea dentata)|access-date=10 May 2024}} In contrast, the Allegheny chinquapin produces one nut per burr.

Chestnuts are in the Fagaceae family along with beech and oak.{{cite journal |last1=Kremer |first1=Antoine |last2=Abbott |first2=Albert G. |last3=Carlson |first3=John E. |last4=Manos |first4=Paul S. |last5=Plomion |first5=Christophe |last6=Sisco |first6=Paul |last7=Staton |first7=Margaret E. |last8=Ueno |first8=Saneyoshi |last9=Vendramin |first9=Giovanni G. |title=Genomics of Fagaceae |journal=Tree Genetics & Genomes |date=June 2012 |volume=8 |issue=3 |pages=583–610 |doi=10.1007/s11295-012-0498-3|s2cid=16005843 |doi-access=free }} Chestnuts are not closely related to the horse chestnut, which is in the family Sapindaceae.{{cite journal |last1=Krahulcová |first1=Anna |last2=Trávníček |first2=Pavel |last3=Krahulec |first3=František |last4=Rejmánek |first4=Marcel |title=Small genomes and large seeds: chromosome numbers, genome size and seed mass in diploid Aesculus species (Sapindaceae) |journal=Annals of Botany |date=8 January 2017 |volume=119 |issue=6 |pages=957–964 |doi=10.1093/aob/mcw261|pmid=28065925 |pmc=5604552 }} Phylogenetic analysis indicates a westward migration of extant Castanea species from Asia to Europe to North America, with the American chestnut more closely related to the Allegheny chinquapin (Castanea pumila v. pumila) than to European or Asian clades. The genomic range of chestnuts can be roughly divided into a clinal pattern of northeast, central, and southwest populations, with southwest populations showing greatest diversity, reflecting an evolutionary bottleneck likely caused by Quaternary glaciation.{{cite journal |last1=Sandercock |first1=Alexander M. |last2=Westbrook |first2=Jared W. |last3=Zhang |first3=Qian |last4=Johnson |first4=Hayley A. |last5=Saielli |first5=Thomas M. |last6=Scrivani |first6=John A. |last7=Fitzsimmons |first7=Sara F. |last8=Collins |first8=Kendra |last9=Perkins |first9=M. Taylor |last10=Craddock |first10=J. Hill |last11=Schmutz |first11=Jeremy |last12=Grimwood |first12=Jane |last13=Holliday |first13=Jason A. |title=Frozen in time: rangewide genomic diversity, structure, and demographic history of relict American chestnut populations |journal=Molecular Ecology |date=26 July 2022 |volume=31 |issue=18 |pages=4640–4655 |doi=10.1111/mec.16629|pmid=35880415 |bibcode=2022MolEc..31.4640S |s2cid=251068122 |doi-access=free }} Two lineages of American chestnut have been identified, one a hybrid between the American chestnut and the Allegheny chinquapin from the southern Appalachians. The other lineage shows a gradual loss of genetic diversity along a northward vector, indicating possible expansion of range following the most recent glacial maximum during the Wisconsin glaciation.{{cite journal |last1=Dane |first1=Fenny |last2=Wang |first2=Zhuoyu |last3=Goertzen |first3=Leslie |title=Analysis of the complete chloroplast genome of Castanea pumila var. pumila, the Allegheny chinkapin |journal=Tree Genetics & Genomes |date=February 2015 |volume=11 |issue=1 |page=14 |doi=10.1007/s11295-015-0840-7|s2cid=18860364 }} Ozark chinkapin (C. ozarkensis), which is typically considered either a distinct species or a subspecies of the Allegheny chinquapin (C. pumila subsp. ozarkensis), may be ancestral to both the American chestnut and the Allegheny chinquapin.{{Cite journal|last1=Huang|first1=Hongwen|last2=Hawkins|first2=Leigh K.|last3=Dane|first3=Fenny|date=1999-11-01|title=Genetic Variation and Population Structure of Castanea pumila var. ozarkensis|journal=Journal of the American Society for Horticultural Science|language=en-US|volume=124|issue=6|pages=666–670|doi=10.21273/JASHS.124.6.666|issn=2327-9788|doi-access=free}}{{Cite web |url=https://www.nationalgeographic.com/environment/article/saving-chestnut-trees-ozarks |first=Robert |last=Langellier |archive-url=https://web.archive.org/web/20190626124603/https://www.nationalgeographic.com/environment/2019/06/saving-chestnut-trees-ozarks/|url-status=live|archive-date=June 26, 2019|title=A legendary Ozark chestnut tree, thought extinct, is rediscovered|date=2019-06-24|website=National Geographic |access-date=2019-07-28}} A natural hybrid of C. dentata and C. pumila has been named Castanea × neglecta.{{r|powo49294-2}}

The American chestnut population was reduced to 1–10% of its original size as a result of the chestnut blight and has not recovered.{{cite journal |last1=Van Drunen |first1=Stephen G. |last2=Schutten |first2=Kerry |last3=Bowen |first3=Christine |last4=Boland |first4=Greg J. |last5=Husband |first5=Brian C. |title=Population dynamics and the influence of blight on American chestnut at its northern range limit: Lessons for conservation |journal=Forest Ecology and Management |date=September 2017 |volume=400 |pages=375–383 |doi=10.1016/j.foreco.2017.06.015|bibcode=2017ForEM.400..375V }} The surviving trees are "frozen in time" with shoots re-sprouting from survivor rootstock but almost entirely undergoing blight-induced dieback without producing chestnuts. Unexpectedly, American chestnut appears to have retained substantial genetic diversity following the population bottleneck, which is at odds with the limited incidence of blight resistance/tolerance in extant populations.{{cite journal |last1=Stoltz |first1=Sophia S. |last2=Husband |first2=Brian C. |title=High genetic diversity in American chestnut (Castanea dentata) despite a century of decline |journal=Conservation Genetics |date=10 November 2022 |volume=24 |pages=25–39 |doi=10.1007/s10592-022-01473-3|s2cid=253470197 }}

The pre-blight distribution was restricted to moist, well-drained, steep slopes with acidic loam soils.{{cite journal |last1=Tulowiecki |first1=Stephen J. |title=Modeling the historical distribution of the American chestnut (Castanea dentata) for potential restoration in western New York State, US |journal=Forest Ecology and Management |date=April 2020 |volume=462 |page=118003 |doi=10.1016/j.foreco.2020.118003|bibcode=2020ForEM.46218003T |s2cid=212766961 }}{{cite journal |last1=Russell |first1=Emily W. B. |title=Pre-Blight Distribution of Castanea dentata (Marsh.) Borkh |journal=Bulletin of the Torrey Botanical Club |date=April 1987 |volume=114 |issue=2 |pages=183–190 |doi=10.2307/2996129|jstor=2996129 }} According to analysis of old forest dust data, the tree was rare or absent in New England prior to 2,500 years before present{{cite journal |last1=Paillet |first1=Frederick L. |title=Chestnut: history and ecology of a transformed species |journal=Journal of Biogeography |date=October 2002 |volume=29 |issue=10–11 |pages=1517–1530 |doi=10.1046/j.1365-2699.2002.00767.x|bibcode=2002JBiog..29.1517P |s2cid=53319372 }} but rapidly established dominance in these forests, becoming a common tree over a range from Maine and southern Ontario to Mississippi, and from the Atlantic coast to the Appalachian Mountains and the Ohio Valley. Within its range, the American chestnut was the dominant timber of mountain ridges and sandstone soils. Along the Blue Ridge Mountains of North Carolina, it dominated the area above the range of the Eastern hemlock and below 1,500 meters.{{cite book |isbn=978-1-332-06695-7 |orig-date=1905 |title=Report on an Examination of a Forest Tract in Western North Carolina (Classic Reprint) |last1=Reed |first1=Franklin W. |date=July 28, 2015 |publisher=FB&C Limited }} In Western Maryland, it comprised 50% of ridge timber and 36% of forested slopes.Dorsey, Clarence Wilbur, George Curtis Martin, Oliver Lanard Fassig, Hugh M. Curran, Edwin G. Paul, and Henry Albert Pressey. Garrett County. Vol. 2. Johns Hopkins Press, 1902.

The tree's abundance was the result of a combination of rapid growth, relative fire resistance, and a large annual nut crop, in comparison to oaks, which do not reliably produce sizable numbers of acorns every year. Historically, the mean fire return interval was 20 years or less in chestnut-predominant ecologies, with a forest stand pattern that was more open than is currently the case.{{cite journal |last1=Kane |first1=Jeffrey M. |last2=Varner |first2=J. Morgan |last3=Stambaugh |first3=Michael C. |last4=Saunders |first4=Michael R. |title=Reconsidering the fire ecology of the iconic American chestnut |journal=Ecosphere |date=October 2020 |volume=11 |issue=10 |doi=10.1002/ecs2.3267|bibcode=2020Ecosp..11E3267K |s2cid=224943591 |doi-access=free }}

The American chestnut was an important tree for wildlife, providing much of the fall mast for species such as white-tailed deer, wild turkey, Allegheny woodrat and (prior to its extinction) the passenger pigeon. Black bears were also known to eat the nuts to fatten up for the winter. The tree contains more nitrogen, phosphorus, potassium and magnesium in its leaves than other trees that share its habitat, so they return more nutrients to the soil which helps with the growth of other plants, animals, and microorganisms.{{cite magazine |last=Jabr |first=Ferris |url=https://www.scientificamerican.com/article/chestnut-forest-a-new-generation-of-american-chestnut-trees-may-redefine-americas-forests/ |title=A New Generation of American Chestnut Trees May Redefine America's Forests |magazine=Scientific American |date=March 1, 2014 |access-date=September 22, 2015 }} The American chestnut is preferred by some avian seed hoarders and was particularly important as a food source during years where the oak mast failed.{{cite journal |last1=Wright |first1=James R. |last2=Matthews |first2=Stephen N. |last3=Pinchot |first3=Cornelia C. |last4=Tonra |first4=Christopher M. |title=Preferences of avian seed-hoarders in advance of potential American chestnut reintroduction |journal=Forest Ecology and Management |date=May 2022 |volume=511 |page=120133 |doi=10.1016/j.foreco.2022.120133|s2cid=247469499 |doi-access=free |bibcode=2022ForEM.51120133W }} The functional extinction of the American chestnut may have resulted in the extinction of some of the tree's host-specialist insect associates, including the Greater Chestnut Weevil.{{cite journal |last1=Charles |first1=Michael A. |last2=McKenna |first2=Duane D. |title=Did the Functional Extinction of the American Chestnut, Castanea dentata, Result in the Extinction of the Greater Chestnut Weevil, Curculio caryatrypes? |journal=Northeastern Naturalist |date=2 January 2024 |volume=30 |issue=4 |doi=10.1656/045.030.0413}}

File:Castanea dentata - blight 1.jpg

The appearance of invasive pathogens of the American Chestnut into the eastern deciduous forest ecosystem is just one instance of the Columbian exchange of pathogens. While the Columbian exchange moved valuable crops between the Americas, Europe and Asia, there was also a downside, as the rapid introduction of invasive and unfamiliar pathogens resulted in serious damage or extinction of some host species.Mack, Richard N., Daniel Simberloff, W. Mark Lonsdale, Harry Evans, Michael Clout, and Fakhri A. Bazzaz. "Biotic invasions: causes, epidemiology, global consequences, and control." Ecological applications 10, no. 3 (2000): 689-710.

{{main|Cryphonectria parasitica}}

Prior to the chestnut blight, the American chestnut was a dominant tree in the ecosystem of the eastern deciduous forest. It was said that a squirrel could walk from New England to Georgia solely on the branches of American chestnuts.{{cite web |title=The Resurrection Of The American Chestnut |url=https://www.sciencefriday.com/segments/the-american-chestnut/ |website=Science Friday}} Once an important hardwood timber tree, the American chestnut suffered a catastrophic population collapse due to the chestnut blight, a disease caused by an Asian bark fungus (Cryphonectria parasitica, formerly Endothia parasitica). The fungus was introduced when infected Japanese chestnut trees were brought to North America in the late 19th century.{{cite journal |last=Ronsheim |first=Margaret L. |date=Feb 2022 |title=Invasive species |journal=AccessScience |publisher=McGraw-Hill Education |doi=10.1036/1097-8542.350480}} Chestnut blight was first noticed on American chestnut trees in what was then the New York Zoological Park, now known as the Bronx Zoo, in the borough of The Bronx, New York City, in 1904, by chief forester Hermann Merkel. Merkel estimated that by 1906 blight had infected 98 percent of the chestnut trees in the borough.{{cite book |last=Merkel |first=Hermann W. |url=https://books.google.com/books?id=xsdLAAAAYAAJ&dq=Hermann+Merkel+chestnuts&pg=PA97 |title=A Deadly Fungus on the American Chestnut |publisher=Nabu Press |year=2011 |isbn=978-1-245-32858-6 |series=Annual Report of the New York Zoological Society |volume=10 |location=Charleston, South Carolina |access-date=October 25, 2015 |via=Google Books |orig-date=1906}} While Asian chestnut species evolved with the blight and developed a strong resistance, the American chestnut and Allegheny chinquapin have little resistance.{{cite journal |last1=Newhouse |first1=Andrew E. |last2=Spitzer |first2=Jesse E. |last3=Maynard |first3=Charles A. |last4=Powell |first4=William A. |title=Chestnut Leaf Inoculation Assay as a Rapid Predictor of Blight Susceptibility |journal=Plant Disease |date=January 2014 |volume=98 |issue=1 |pages=4–9 |doi=10.1094/PDIS-01-13-0047-RE|pmid=30708571 |doi-access=free |bibcode=2014PlDis..98....4N }}{{cite book |author1-link=Kan Wang |last=Wang |first=Kan |title=Agrobacterium Protocols |series=Methods in Molecular Biology |publisher=Humana Press |publication-place=New York, NY |year=2015 |volume=1224 |isbn=978-1-4939-1657-3 |oclc=898898245 |pages=vii-viii |doi=10.1007/978-1-4939-1658-0 |pmid=25568905 |s2cid=3705500}} {{ISBN|978-1-4939-1657-3}}.{{rp|145}}{{cite journal | last1=Barnes | first1=Jessica C | last2=Delborne | first2=Jason A | title=The politics of genetic technoscience for conservation: The case of blight-resistant American chestnut | journal=Environment and Planning E: Nature and Space | publisher=Sage | date=2021-06-24 | volume=5 | issue=3 | issn=2514-8486 | doi=10.1177/25148486211024910 | page=251484862110249 | s2cid=236783237| doi-access=free }} The airborne bark fungus spread {{convert|50|mi|km|abbr=on}} per year and in a few decades girdled and killed more than three billion American chestnut trees. Salvage logging during the early years of the blight may have unwittingly destroyed trees that had high levels of resistance to the disease and thus aggravated the calamity.{{cite journal |last=Detwiler |first=Samuel |url=https://books.google.com/books?id=UFQyAQAAMAAJ&dq=Samuel+Detwiler+1915+american+chestnut&pg=PA953 |title=The American Chestnut Tree: Identification and Characteristics |journal=American Forestry |volume=21 |issue=362 |date=October 1915 |page=957-959 |location=Washington D.C. |publisher=American Forestry Association |via=Google Books |access-date=October 25, 2015 }} New shoots often sprout from the roots when the main stem dies, so the species has not yet become extinct. However, the stump sprouts rarely reach more than {{convert|6|m|ft|0|abbr=on}} in height before blight infection returns, so the species is classified as functionally extinct{{Cite web|url=https://www.tacf.org/the-american-chestnut/history-american-chestnut/|title=History of the American Chestnut|website=The American Chestnut Foundation|language=en-US|access-date=2020-02-28}} since the chestnut blight only actively kills the above ground portion of the American chestnut tree, leaving behind the below-ground components such as the root systems. It was recorded in the 1900s that the chestnut blight would commonly reinfect any novel stems that grew from the stumps, therefore maintaining a cycle that would prevent the American chestnut tree from re-establishing.{{Cite web |url=http://www.arnoldia.arboretum.harvard.edu/pdf/articles/1992-52-2-evolution-of-the-chestnut-tree-and-its-blight.pdf|title=Evolution of the Chestnut Tree and its Blight|last=Anagnostakis|first=Sandra|archive-url=https://web.archive.org/web/20170505133607/http://arnoldia.arboretum.harvard.edu/pdf/articles/1992-52-2-evolution-of-the-chestnut-tree-and-its-blight.pdf|archive-date=May 5, 2017}} However, some American chestnut trees have survived because of a small natural resistance to the chestnut blight.{{Cite journal |last1=Dierauf|first1=Tom |first2=Joel |last2=Artman |first3=John R. |last3=Elkins |first4=S. Lucille |last4=Griffin |first5=Gary J. |last5=Griffin |s2cid=83066643 |title=High Level of Chestnut Blight Control on Grafted American Chestnut Trees Inoculated with Hypovirulent Strains |journal=Journal of Arboriculture |volume=23 |issue=2 |date=March 1997 |pages=87–88 |doi=10.48044/jauf.1997.013 |url=https://joa.isa-arbor.com/articles.asp?JournalID=1&VolumeID=23&IssueID=2|doi-access=free }}

The high density of American chestnuts within its range and the lack of natural immunity allowed the blight to spread quickly and cause infection and die-off in nearly every tree exposed. Early attempts to treat chestnut blight were both chemical (such as the use of fungicides) and physical (such as removing infected limbs through tree surgery and the removal of infected trees from cultivated and wild stands). Quarantine measures were also put into place, with the later support of the Plant Quarantine Act, which was an attempt to prevent the importation of other potential plant pathogens. These attempts to contain the spread of chestnut blight were unsuccessful; the devastation of the species was worsened because the chestnut blight resulted in isolation of remaining specimens, resulting in asexual propagation of many isolated American chestnuts, low genetic diversity of stands of American chestnuts, and consequent vulnerability to extirpation.{{cite journal |last1=Stilwell |first1=Kevin L. |last2=Wilbur |first2=Henry M. |last3=Werth |first3=Charles R. |last4=Taylor |first4=Douglas R. |title=Heterozygote advantage in the American chestnut, Castanea dentata (Fagaceae) |journal=American Journal of Botany |date=February 2003 |volume=90 |issue=2 |pages=207–213 |doi=10.3732/ajb.90.2.207|pmid=21659110 }}

Chestnut blight is not to be confused with sun scald, where winter sun reflects off of snow, warming the bark on the sun-facing trunk (this is the south-facing trunk in the Northern Hemisphere). This snow-reflected sunlight repeatedly warms and thaws the trunk during the day, resulting in vulnerability of the bark and cambium to freezing cold temperatures during the subsequent night, eventually resulting in bark cankers that resemble chestnut blight. Also, sun scald makes the damaged bark vulnerable to invasion by pathogens.{{cite web |title=Diseases |url=https://www.canr.msu.edu/chestnuts/pest_management/diseases |website=Chestnuts |language=en}}

{{Main|Phytophthora cinnamomi}}

Before the onset of chestnut blight and prior to 1824, an epidemic of ink disease struck American chestnuts, most likely brought to the southern United States on Cork oak trees imported from Portugal.{{cite journal |author=Anagnostakis |first=Sandra L. |date=October 2012 |title=Chestnut Breeding in the United States for Disease and Insect Resistance |journal=Plant Disease |publisher=The American Phytopathological Society |volume=96 |issue=10 |pages=1392–1403 |doi=10.1094/PDIS-04-12-0350-FE |issn=0191-2917 |pmid=30727322 |doi-access=free|bibcode=2012PlDis..96.1392A }} This fungal pathogen is known to also kill the roots and collars of several Castanea species, including the European sweet chestnut. It affected primarily chestnuts in the Southeastern US and at the later time when chestnut blight struck, the range of C. dentata may have already been reduced. The potential range of blight-resistant American chestnuts is substantially reduced if those chestnuts are susceptible to ink disease.{{cite journal |last1=Gustafson |first1=Eric J. |last2=Miranda |first2=Brian R. |last3=Dreaden |first3=Tyler J. |last4=Pinchot |first4=Cornelia C. |last5=Jacobs |first5=Douglass F. |title=Beyond blight: Phytophthora root rot under climate change limits populations of reintroduced American chestnut |journal=Ecosphere |date=February 2022 |volume=13 |issue=2 |doi=10.1002/ecs2.3917|bibcode=2022Ecosp..13E3917G |s2cid=246665585 |doi-access=free }} Further, the range of this pathogen will extend northward as the climate warms, which may further limit the potential range of the American chestnut.{{cite journal |last1=Gustafson |first1=Eric J. |last2=Miranda |first2=Brian R. |last3=Dreaden |first3=Tyler J. |last4=Pinchot |first4=Cornelia C. |last5=Jacobs |first5=Douglass F. |title=Beyond blight: Phytophthora root rot under climate change limits populations of reintroduced American chestnut |journal=Ecosphere |date=February 2022 |volume=13 |issue=2 |doi=10.1002/ecs2.3917|bibcode=2022Ecosp..13E3917G |doi-access=free }} Potassium phosphonate has been found to induce resistance to infection of C. sativa by both inhibiting Phytophthora species directly and by improving the host response, inducing resistance to lesions in phloem tissue and formation of callus.{{cite journal |last1=Brandano |first1=Andrea |last2=Serra |first2=Salvatorica |last3=Hardy |first3=Giles E. St. J. |last4=Scanu |first4=Bruno |title=Potassium Phosphonate Induces Resistance in Sweet Chestnut against Ink Disease Caused by Phytophthora Species |journal=Pathogens |date=22 February 2023 |volume=12 |issue=3 |page=365 |doi=10.3390/pathogens12030365 |pmid=36986287 |pmc=10054612 |doi-access=free }} Whether or not this effect would occur in C. dentata is uncertain.{{cite journal |last1=Vannini |first1=Andrea |last2=Morales-Rodriguez |first2=Carmen |title=Phytophthora diseases |journal=Forest Microbiology |date=2022 |pages=379–402 |doi=10.1016/B978-0-323-85042-1.00016-1|isbn=978-0-323-85042-1 }}

{{Main|Gnomoniopsis castaneae}}

Brown nut rot is a destructive plant disease caused by the primary agent Gnomoniopsis castaneae and afflicting Castanea species. This pathogen also causes mild disease or exists as an endophyte in other hardwoods. The disease is found in Europe and Oceania. More recently, it has been reported in North America.{{cite journal |last1=Dobry |first1=Emily |last2=Campbell |first2=Michael |title=Gnomoniopsis castaneae: An emerging plant pathogen and global threat to chestnut systems |journal=Plant Pathology |date=February 2023 |volume=72 |issue=2 |pages=218–231 |doi=10.1111/ppa.13670|s2cid=253452637 |doi-access=free |bibcode=2023PPath..72..218D }}

{{Main|Dryocosmus kuriphilus}}

The Chinese gall wasp attacks all chestnut species and causes heavy damage.{{cite journal |last1=Zhu |first1=Cancan |last2=Shi |first2=Fenghou |last3=Chen |first3=Yu |last4=Wang |first4=Min |last5=Zhao |first5=Yuqiang |last6=Geng |first6=Guomin |title=Transcriptome Analysis of Chinese Chestnut (Castanea mollissima Blume) in Response to Dryocosmus kuriphilus Yasumatsu Infestation |journal=International Journal of Molecular Sciences |date=15 February 2019 |volume=20 |issue=4 |page=855 |doi=10.3390/ijms20040855|pmid=30781446 |pmc=6412832 |doi-access=free }} As this species of wasp is a threat to saplings, and is now widely-present in eastern North American forests, it is a potential problem for reintroduction of the American chestnut. The Chinese parasitoid chalcid wasp Torymus sinensis {{small|Kamijo}} is considered an effective control method for the Chinese gall wasp.Carol Mapes. The Nutshell 76(1) · Spring 2022. https://www.researchgate.net/profile/Carol-Mapes/publication/360143571_The_Asian_Chestnut_Gall_Wasp_in_North_America/links/626447898cb84a40ac845cd8/The-Asian-Chestnut-Gall-Wasp-in-North-America.pdf. There are now established populations of Torymus sinensis in North America.{{cite journal |last1=Avtzis |first1=Dimitrios N. |last2=Melika |first2=George |last3=Matošević |first3=Dinka |last4=Coyle |first4=David R. |title=The Asian chestnut gall wasp Dryocosmus kuriphilus: a global invader and a successful case of classical biological control |journal=Journal of Pest Science |date=January 2019 |volume=92 |issue=1 |pages=107–115 |doi=10.1007/s10340-018-1046-1|bibcode=2019JPesS..92..107A |s2cid=59528127 }}

American chestnuts were a common part of the forest canopy in much of its original range. Although large trees are currently rare east of the Mississippi River, they exist in pockets in the blight-free West, where the habitat was agreeable for planting: settlers took seeds with them in the 19th century. Huge planted chestnut trees can be found in Sherwood, Oregon,{{Cite web|title=Oregon Chestnut Trees|url=https://www.tacf.org/nc-sc/photos/oregon-chestnut-trees/|access-date=2020-07-28|website=The American Chestnut Foundation|language=en-US|archive-date=November 28, 2020|archive-url=https://web.archive.org/web/20201128021600/https://tacf.org/nc-sc/photos/oregon-chestnut-trees/}} as the Mediterranean climate of the West Coast discourages the fungus, which relies on hot, humid summer weather. American chestnut also thrives as far north as Revelstoke, British Columbia.{{Cite web|title=A Decade of Progress|url=http://www.canadianchestnutcouncil.ca/index.cfm?page=decadeOfProgress|access-date=2020-07-28|website=canadianchestnutcouncil.ca}}

At present, it is believed that survival of C. dentata for more than a decade in its native range is almost impossible. The fungus uses various oak trees as a host,{{Cite web|url=http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/diseases/cankers/chestnut-blight.aspx|title=Chestnut Blight|last=Garden|first=Missouri Botanical|website=missouribotanicalgarden.org|language=en-US|access-date=2017-05-07}} and while the oak is unaffected, American chestnuts nearby will succumb to the blight in approximately a year or more.{{Cite web|url=http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Cryphonectria_parasitica.htm|title=Cryphonectria_parasitica|website=www.columbia.edu|access-date=2017-05-07}} In addition, the hundreds of chestnut stumps and "living stools" dotting eastern woodlands may still contain active pathogens. It is considered extirpated from Florida and Illinois.

The reduced population of American chestnuts directly impacted many species of insects that relied upon the tree species for survival. Of approximately 60 species that feed upon the American chestnut, seven rely entirely on the American chestnut as a food source. Some of these, like the American chestnut moth, are now extinct or severely reduced in population.{{cite journal |last=Opler |first=P. A. |date=January 1978 |title=Insects of American chestnut: possible importance and conservation concern |journal=The American Chestnut Symposium |pages=83–85 |location=Morgantown, West Virginia |publisher=West Virginia University Press |url=https://rngr.net/publications/chestnut/1978/insects-of-american-chestnut-possible-importance-and-conservation-concern/at_download/file }}

File:castanea dentata-field trial2009.jpg

File:Tower Hill Botanic Garden - American chestnuts.jpg at Tower Hill Botanic Garden in Massachusetts]]

Researchers at the State University of New York College of Environmental Science and Forestry (SUNY ESF) have developed the Darling 58 chestnut cultivar. This cultivar expresses the gene for wheat oxalate oxidase enzyme, which breaks down the oxalic acid produced by the blight fungus, preventing the death of the tree. When pollen of transgenic fathers fertilizes an ovule of a native mother in the field, those resulting seedlings that express the oxalate oxidase enzyme show growth similar to non-transgenic full siblings, indicating that the transgene does not impede growth under field conditions.{{cite journal |last1=Riendeau |first1=Tyler |title=Advancing American Chestnut (Castanea Dentata) Restoration Through Science, GIS And Partnerships |url=https://dune.une.edu/theses/444/ |website=All Theses And Dissertations |date=1 July 2023}} The modified chestnut does not affect survival, pollen use, or reproduction of bumble bees.{{cite journal |last1=Newhouse |first1=Andrew E. |last2=Allwine |first2=Anastasia E. |last3=Oakes |first3=Allison D. |last4=Matthews |first4=Dakota F. |last5=McArt |first5=Scott H. |last6=Powell |first6=William A. |title=Bumble bee (Bombus impatiens) survival, pollen usage, and reproduction are not affected by oxalate oxidase at realistic concentrations in American chestnut (Castanea dentata) pollen |journal=Transgenic Research |date=10 June 2021 |volume=30 |issue=6 |pages=751–764 |doi=10.1007/s11248-021-00263-w|pmid=34110572 |pmc=8580921 |doi-access=free }} A deregulation petition for the Darling 58 variant has been submitted.[https://www.aphis.usda.gov/sites/default/files/19-309-01p.pdf "Petition for Determination of Nonregulated Status for Blight-Resistant Darling 58 American Chestnut"]. https://www.aphis.usda.gov, Retrieved August 28, 2020.[https://www.federalregister.gov/documents/2020/08/19/2020-18135/state-university-of-new-york-college-of-environmental-science-and-forestry-petition-for "State University of New York College of Environmental Science and Forestry; Petition for Determination of Nonregulated Status for Blight-Resistant Darling 58 American Chestnut"]. https://www.federalregister.gov, August 19, 2020. Retrieved August 28, 2020. If approved, these trees could be the first genetically modified forest trees released in the wild in the United States.{{cite journal |last1=Thompson |first1=Helen |year=2012 |title=Plant science: The chestnut resurrection |journal=Nature |volume=490 |issue=748|pages=22–23 |doi=10.1038/490022a |pmid=23038446 |bibcode=2012Natur.490...22T |doi-access=free }}{{cite news|last=Wines|first=Michael|title=Like-Minded Rivals Race to Bring Back an American Icon|url=https://www.nytimes.com/2013/07/14/us/like-minded-rivals-race-to-bring-back-an-american-icon.html?ref=earth&_r=0|date=July 13, 2013|newspaper=New York Times|access-date=July 14, 2013}}

Unlike American chestnut, Japanese chestnut exhibits resistance to Phytophthora cinnamomi, the fungal pathogen that causes ink disease. The mechanism of resistance of C. crenata to Phytophthora cinnamomi may derive from its expression of the Cast_Gnk2-like gene (99.6% identical with {{UniProt|A0A8J4V9V8}}).{{cite journal |vauthors=Santos C, Nelson CD, Zhebentyayeva T, Machado H, Gomes-Laranjo J, Costa RL |title=First interspecific genetic linkage map for Castanea sativa x Castanea crenata revealed QTLs for resistance to Phytophthora cinnamomi |journal=PLOS ONE |volume=12 |issue=9 |pages=e0184381 |date=2017 |pmid=28880954 |pmc=5589223 |doi=10.1371/journal.pone.0184381 |bibcode=2017PLoSO..1284381S |doi-access=free }} Transgenic modification of C. dentata with the Cast_Gnk2-like gene may provide a mechanism for developing American chestnut trees resistant to Phytophthora cinnamomi. Stacking of the Cast_Gnk2-like gene and the oxalate oxidase gene may provide a means of developing genetically modified American chestnut trees resistant to both the chestnut blight and to ink disease.{{cite journal |last1=McGuigan |first1=Linda |last2=Fernandes |first2=Patrícia |last3=Oakes |first3=Allison |last4=Stewart |first4=Kristen |last5=Powell |first5=William |title=Transformation of American Chestnut (Castanea dentata (Marsh.) Borkh) Using RITA Temporary Immersion Bioreactors and We Vitro Containers |journal=Forests |date=2020-11-13 |volume=11 |issue=11 |page=1196 |doi=10.3390/f11111196|doi-access=free }}

The American Chestnut Research and Restoration Project at SUNY-ESF is not pursuing intellectual property protection through patents. Dr William Powell, the project's co-director, states that the decision to not pursue a patent on the project's transgenic lines was to allow the plant to be more accessible for conservationists and members of the public. Powell posits that a patent would constrain the spread of the oxalate oxidase transgene into American chestnut populations by limiting the ability to freely plant transgenic trees and cross the trees with surviving American chestnuts or the hybrids produced in the backcross program. Powell states that patents would be a barrier to chestnut restoration and in direct opposition to the program's goals of collaboration. While patent protection is not sought, the non-profit American Chestnut Foundation (TACF) maintains control through a Germplasm Agreement, ensuring authorized use of chestnut germplasm. The agreement safeguards TACF's rights and aligns with the organization's restoration goals.

A laboratory error resulted in mistaken use of the Darling 54 cultivar instead of the Darling 58 cultivar in some field trials.{{cite web |last1=Todd |first1=Roxy |title=After GMO program hits snag, what's the future of restoring American chestnuts? |url=https://www.alleghenyfront.org/american-chestnut-blight-genetically-modified/ |website=The Allegheny Front |date=8 March 2024}} TACF and colleagues have also reported decreased growth rates, and poor heritability of resistance of the Darling 58 cultivar.{{cite web |title=TACF Chestnut Chat |url=https://www.youtube.com/watch?v=9w_ehgYyxGY |website=YouTube | date=September 15, 2023 |publisher=The American Chestnut Foundation |access-date=8 June 2024}} In response, the American Chestnut Foundation withdrew its support of development of the Darling 58 cultivar in December 2023.{{Cite web |last=Brindley |first=Hal |date=2023-12-08 |title=Press Release: TACF Discontinues Development of Darling 58 |url=https://tacf.org/tacf-discontinues-development-of-darling-58/ |access-date=2024-06-05 |website=The American Chestnut Foundation |language=en-US}} The American Chestnut Research & Restoration Program at SUNY ESF is continuing to pursue deregulation.{{Cite news |last=Grandoni |first=Dino |date=2023-12-27 |title=Genetic engineering was meant to save chestnut trees. Then there was a mistake. |url=https://www.washingtonpost.com/climate-environment/2023/12/24/chestnut-tree-genetic-engineering-mistake/ |access-date=2024-02-05 |newspaper=Washington Post |language=en-US |issn=0190-8286}}{{Cite web |title=Progress Update 2023 |url=https://www.esf.edu/chestnut/progress-report/2023.php |access-date=2024-02-05 |website=www.esf.edu |language=en}}{{Cite web |title=The American Chestnut Research & Restoration Project at ESF |url=https://www.esf.edu/chestnut/index.php |access-date=2024-06-05 |website=www.esf.edu |language=en}}{{Cite web |last=Brindley |first=Hal |date=2023-12-08 |title=Press Release: TACF Discontinues Development of Darling 58 |url=https://tacf.org/tacf-discontinues-development-of-darling-58/ |access-date=2024-02-05 |website=The American Chestnut Foundation |language=en-US}}{{Cite web |title=Darling 58 |url=https://tacf.org/darling-58/ |access-date=2024-02-05 |website=The American Chestnut Foundation |language=en-US}}

In 2022, the SUNY ESF group developed transgenic American chestnut trees incorporating both the oxalate oxidase transgene from wheat and the win3.12 promoter transgene from the necklace poplar. Unlike the CAMV 35S promoter which acts at all times, this poplar promoter drives OxO expression at a low level under basal conditions, but elevates to high levels under conditions of wounding or tissue infection. In laboratory bioassays, win3.12-OxO lines showed elevated disease tolerance similar to that exhibited by blight-resistant Chinese chestnut.{{cite journal |last1=Carlson |first1=Erik |last2=Stewart |first2=Kristen |last3=Baier |first3=Kathleen |last4=McGuigan |first4=Linda |last5=Culpepper |first5=Tobi |last6=Powell |first6=William |title=Pathogen-induced expression of a blight tolerance transgene in American chestnut |journal=Molecular Plant Pathology |date=March 2022 |volume=23 |issue=3 |pages=370–382 |doi=10.1111/mpp.13165|pmid=34841616 |pmc=8828690 |bibcode=2022MolPP..23..370C }} Limiting expression of the OxO gene to blight infected tissues is expected to reduce the metabolic cost of gene expression, resulting in increased competitiveness of these new cultivars. As of January 2025, the win3.12 OxO chestnut is still in the research and development phase and has not been deployed for restoration purposes.{{cite web |title=Darling 58 /54 {{!}} The American Chestnut Foundation |url=https://tacf.org/darling-58/}}

{{main|American Chestnut Cooperators' Foundation}}

File:Floyda.jpg

American Chestnut Cooperators' Foundation (ACCF) is not using crosses with Asian species for blight resistance, but intercrossing among American chestnuts selected for native resistance to the blight, a breeding strategy described by the ACCF as "All-American intercrosses". John Rush Elkins, a research chemist and professor emeritus of chemistry at Concord University, and Gary Griffin, professor of plant pathology at Virginia Tech, think there may be several different characteristics which favor blight resistance. Both Elkins and Griffin have written extensively about the American chestnut.[http://www.accf-online.org/biblio.html "Bibliography."] {{Webarchive|url=https://web.archive.org/web/20160305080130/http://www.accf-online.org/biblio.html |date=March 5, 2016 }} www.accf-online.org. Retrieved January 11, 2016. They believe that by making intercrosses among resistant American chestnuts from many locations, they will continue to improve upon the levels of blight resistance to make an American chestnut that can compete in the forest. Griffin, who has been involved with American chestnut restoration for many years, developed a scale for assessing levels of blight resistance, which made it possible to make selections scientifically. He inoculated five-year-old chestnuts with a standard lethal strain of the blight fungus and measured growth of the cankers. Chestnuts with no resistance to blight make rapid-growing, sunken cankers that are deep and kill tissue right to the wood. Resistant chestnuts make slow-growing, swollen cankers that are superficial: live tissue can be recovered under these cankers. The level of blight resistance is judged by periodic measurement of cankers. Grafts from large survivors of the blight epidemic were evaluated following inoculations, and controlled crosses among resistant American chestnut trees were made beginning in 1980. The first "All-American intercrosses" were planted in Virginia Tech's Martin American Chestnut Planting in Giles County, Virginia, and in Beckley, West Virginia. They were inoculated in 1990 and evaluated in 1991 and 1992. Nine of the trees showed resistance equal to their parents, and four of these had resistance comparable to hybrids in the same test.Griffin, G. J., J. R. Elkins, D. McCurdy, and S. L. Griffin. [http://ecosystems.psu.edu/research/chestnut/information/conference-2004/conference/griffin "Integrated use of resistance, hypovirulence, and forest management to control blight on American chestnut."] www.ecosystems.psu.edu, 2005.[https://archive.org/stream/restorationofame00stei/restorationofame00stei_djvu.txt "Restoration of American Chestnut to Forest Lands: Proceedings of a Conference and Workshop Held May 4-6, 2004 at The North Carolina Arboretum."] www.archive.org. Retrieved January 22, 2016.[http://www.accf-online.org/breed.html "Breeding for Blight Resistance."] {{Webarchive|url=https://web.archive.org/web/20160304215224/http://www.accf-online.org/breed.html |date=March 4, 2016 }} www.accf-online.org. Retrieved January 11, 2016. Many ACCF chestnuts have expressed blight resistance equal to or greater than an original blight survivor but so far, only a handful have demonstrated superior, durable blight control. Time will tell if the progeny of these best chestnuts exhibit durable blight resistance in different stress environments.[http://www.accf-online.org/news.html "American Chestnut Cooperators' Foundation 2015 Newsletter: Grower Reports."] {{Webarchive|url=https://web.archive.org/web/20160122062941/http://www.accf-online.org/news.html |date=January 22, 2016 }} www.accf-online.org. Retrieved January 11, 2015.

Backcrossing as a treatment for blight was first proposed by Charles Burnham of the University of Minnesota in the 1970s.[http://www.charliechestnut.org/Phase1/Scrapbook/Conservation3AGenetic.html "Conservation - Genetic Research"] {{Webarchive|url=https://web.archive.org/web/20160427063734/http://www.charliechestnut.org/Phase1/Scrapbook/Conservation3AGenetic.html |date=April 27, 2016 }}. www.charliechestnut.org. Retrieved January 12, 2016. Burnham, a professor emeritus in agronomy and plant genetics who was considered one of the pioneers of maize genetics,Galloway, Paul R. [http://www.tacf.org/pdfs/chapters/VTNH/My%20Chestnut%20Story%20-%20Paul%20Galloway.pdf "My Chestnut Story"] {{Webarchive|url=https://web.archive.org/web/20161027081123/http://www.tacf.org/pdfs/chapters/VTNH/My%20Chestnut%20Story%20-%20Paul%20Galloway.pdf |date=October 27, 2016 }}. www.tacf.org. Retrieved October 5, 2015. realized that experiments conducted by the USDA to cross-breed American chestnuts with European and Asian chestnuts erroneously assumed that a large number of genes were responsible for blight resistance, while it is currently believed the number of responsible genes is low. The USDA abandoned their cross-breeding program and destroyed local plantings around 1960 after failing to produce a blight-resistant hybrid.{{cite journal |last1=Burnham |first1=Charles R |year=1986 |title=Chestnut Hybrids from the USDA-Connecticut Breeding Programs |url=http://ecosystems.psu.edu/research/chestnut/information/journal/vol1-issue2 |journal=The Journal of the American Chestnut Foundation |volume=1 |issue=2|pages=8–13 }} Burnham's recognition of the USDA's error led to him joining with others to create The American Chestnut Foundation in 1983, with the sole purpose of breeding a blight-resistant American chestnut. The American Chestnut Foundation is backcrossing blight-resistant Chinese chestnut into American chestnut trees, to recover the American growth characteristics and genetic makeup, and then finally intercrossing the advanced backcross generations to eliminate genes for susceptibility to blight.Valigra, Lori. [https://web.archive.org/web/20060104013902/http://news.nationalgeographic.com/news/2005/12/1229_051229_chestnut.html "Back-Breeding Could Restore Chestnut Trees Ravaged by Blight"]. National Geographic News, December 29, 2005. Retrieved September 26, 2015. The first backcrossed American chestnut tree, called "Clapper", survived blight for 25 years, and grafts of the tree have been used by The American Chestnut Foundation since 1983. The Pennsylvania chapter of The American Chestnut Foundation, which seeks to restore the American chestnut to the forests of the Mid-Atlantic states, has planted over 22,000 trees.[http://www.tacf.org/pdfs/resources/planting_manual.pdf "Planting and growing chestnut trees"] {{Webarchive|url=https://web.archive.org/web/20160304074428/http://www.tacf.org/pdfs/resources/planting_manual.pdf |date=March 4, 2016 }}. www.tacf.org. Retrieved January 15, 2016.

The Surface Mining Control and Reclamation Act of 1977 requires owners of abandoned coal mines to cover at least 80 percent of their land with vegetation. While many companies planted invasive grasses, others began funding research on planting trees, because they can be more cost-effective, and yield better results.Barnes, Philip. [https://www.ohio.edu/research/communications/gilland.cfm "Return of the Native: Biologists revive the chestnut tree at former coal mine sites"] {{Webarchive|url=https://web.archive.org/web/20151001195133/https://www.ohio.edu/research/communications/gilland.cfm |date=October 1, 2015 }}. www.ohio.edu. Retrieved September 30, 2015. Keith Gilland began planting American chestnut trees in old strip mines in 2008 as a student at Miami University, and to date has planted over 5,000 trees. In 2005, a hybrid tree with mostly American genes was planted on the lawn of the White House.{{cite news

|title=Trying to Light A Fire Under Chestnut Revival

|newspaper=The Washington Post

|date=December 29, 2005

|url=https://www.washingtonpost.com/wp-dyn/content/article/2005/12/28/AR2005122801235.html

|access-date=October 29, 2010 }} A tree planted in 2005 in the tree library outside the USDA building was still very healthy seven years later; it contains 98% American chestnut DNA and 2% Chinese chestnut DNA. This tree contains enough Chinese chestnut DNA that encodes for systemic resistance genes to resist the blight. This is essential for restoring the American chestnut trees into the Northeast.[https://web.archive.org/web/20110703095726/http://greenxc.com/2011/american-chestnut-restoration-breakthrough-tale-tree/ "American Chestnut Restoration Breakthrough: The Tale of a Tree"]. Wayback Machine. www.greenxc.com, June 28, 2011. Retrieved September 23, 2014. The Northern Nut Growers Association (NNGA) has also been active in pursuing viable hybrids.[http://www.nutgrowing.org/ng-american-chestnut.htm "Nut Grower's Guide--Chestnut: American Chestnut"] {{Webarchive|url=https://web.archive.org/web/20150923060209/http://www.nutgrowing.org/ng-american-chestnut.htm |date=September 23, 2015 }}. Northern Nut Growers Association, Inc. www.nutgrowing.org. Retrieved September 22, 2015. From 1962 to 1990, Alfred Szego and other members of the NNGA developed hybrids with Chinese varieties which showed limited resistance. Initially the backcrossing method would breed a hybrid from an American chestnut nut and a Chinese chestnut, the hybrid would then be bred with a normal American chestnut, subsequent breeding would involve a hybrid and an American chestnut or two hybrids, which would increase the genetic makeup of the hybrids primarily American chestnut but still retain the blight resistance of the Chinese chestnut.{{Cite journal|last=Burnham|first=Charles R.|date=1988|title=The Restoration of the American Chestnut: Mendelian genetics may solve a problem that has resisted other approaches|journal=American Scientist|volume=76|issue=5|pages=478–487|jstor=27855387|issn=0003-0996}}

A backcross breeding program has integrated desirable American chestnut traits with traits from the Chinese chestnut, achieving intermediate resistance to Cryphonectria parasitica and Phytophthora cinnamomi in the hybrid genome.{{cite journal |last1=Clark |first1=Stacy L. |last2=Schlarbaum |first2=Scott E. |last3=Saxton |first3=Arnold M. |last4=Jeffers |first4=Steven N. |last5=Baird |first5=Richard E. |title=Eight-year field performance of backcross American chestnut (Castanea dentata) seedlings planted in the southern Appalachians, USA |journal=Forest Ecology and Management |date=March 2023 |volume=532 |page=120820 |doi=10.1016/j.foreco.2023.120820|s2cid=256572816 |doi-access=free |bibcode=2023ForEM.53220820C }}

The B3F3 strain, a product of backcrossing and intercrossing with selection for blight resistance, is approximately 94% American chestnut and 6% Chinese chestnut{{cite magazine|title=Breeding for Resistance: TACF and the Burnham Hypothesis|last=Smith|first=Anna Huckabee|date=March–April 2012|volume=26|issue=2|pages=11–15|magazine=The Journal of the American Chestnut Foundation|url=https://tacf.org/wp-content/uploads/2016/08/Blight-Resistance.pdf|access-date=10 May 2024}}{{cite web|url=https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=444846&isprofile=0&hf=1|title=Castanea hybrid (15/16 B3F3)|website=Plant Finder|publisher=Missouri Botanical Garden|access-date=10 May 2024}} and has been planted experimentally in Maryland in an orchard.{{Cite web |url=https://www.fws.gov/endangered/about/ep_46_2015.html |title=Featured Species {{!}} American chestnut (Episode 46)|website=fws.gov |date=8 October 2015|archive-date=29 October 2020 |archive-url=https://web.archive.org/web/20201029082941/https://www.fws.gov/endangered/about/ep_46_2015.html }}

Hypovirus is the only genus in the family Hypoviridae. Members of this genus infect fungal pathogens and reduce their ability to cause disease (hypovirulence).[http://www.dpvweb.net/notes/showgenus.php?genus=Hypovirus "Notes on Genus: Hypovirus"] {{Webarchive|url=https://web.archive.org/web/20160304093422/http://www.dpvweb.net/notes/showgenus.php?genus=Hypovirus |date=March 4, 2016 }}. www.dpvweb.net. Retrieved October 14, 2015. In particular, the virus infects Cryphonectria parasitica, the fungus that causes chestnut blight, which has enabled infected trees to recover from the blight. The use of hypovirulence to control blight originated in Europe where the fungal virus spread naturally through populations of European chestnuts. The reduced ability of the fungus to cause disease allowed the European chestnut to regenerate, creating large stands of trees. Hypovirulence has also been found in North America, but has not spread effectively.[http://www.tacf.org/FAQ.php "Frequently Asked Questions"] {{Webarchive|url=https://web.archive.org/web/20151020065031/http://www.tacf.org/FAQ.php |date=October 20, 2015 }}. www.tacf.org. Retrieved November 1, 2015. The "Arner Tree" of Southern Ontario is one of the best examples of naturally occurring hypovirulence. It is a mature American chestnut that has recovered from severe infections of chestnut blight. The cankers have healed over and the tree continues to grow vigorously. Scientists have discovered that the chestnut blight remaining on the tree is hypovirulent, although isolates taken from the tree do not have the fungal viruses found in other isolates.[http://www.canadianchestnutcouncil.ca/index.cfm?page=hypovirulence "Hypovirulence"]. www.canadianchestnutcouncil.ca. Retrieved October 14, 2015. Trees inoculated with isolates taken from the Arner tree have shown moderate canker control.[http://ecosystems.psu.edu/research/chestnut/meetings/crees-ne-projects/minutes-pdfs/minutes-2001 "NE-140 Technical Committee Meeting Biological Improvement of Chestnut (Castanea spp.) and Management of Pests"]. www.ecosystem.psu.edu, October 20, 2001. Retrieved October 14, 2015. The cankers of hypovirulent American chestnut trees occur on the outermost tissues of the tree but the cankers do not spread into the growth tissues of the American chestnut tree, thereby providing it with a resistance.{{Cite journal|last=Griffin|first=Gary |title=Blight Control and Restoration of the American Chestnut |journal=Journal of Forestry |volume=98 |issue=2 |date=February 2000 |pages=22–27 |doi=10.1093/jof/98.2.22 |doi-access=free|url=https://academic.oup.com/jof/article/98/2/22/4614209}}

File:Castanea dentata-foliage.jpg

File:American Chestnut, November 2015, Lumpkin Co. GA.jpg

File:Castanea dentata at Oakdale Campus in Coralville, Iowa.jpg

File:AmericanChestnutNovaScotia.jpg]]

• About 2,500 chestnut trees are growing on {{convert|60|acre}} near West Salem, Wisconsin, which is the world's largest remaining stand of American chestnut. These trees are the descendants of those planted by Martin Hicks, an early settler in the area, who planted fewer than a dozen trees in the late 19th century. Planted outside the natural range of chestnut, these trees escaped the initial onslaught of chestnut blight, but in 1987 scientists found blight in the stand. Scientists are working to try to save the trees.{{cite web |last=Childs |first=Gina |url=http://dnr.wi.gov/wnrmag/html/stories/2002/aug02/chest.htm |title=Chestnut's Last Stand |archive-url=https://web.archive.org/web/20100822171751/http://www.dnr.wi.gov/wnrmag/html/stories/2002/aug02/chest.htm |archive-date=August 22, 2010 |work=Wisconsin Natural Resources Magazine |date=August 2002 |via=dnr.wi.gov |access-date=April 19, 2012 }}
• Some 1,348 chestnut trees, varying in size from seedlings to nearly mature trees, are growing in a forest in western Maine. These chestnuts were originally established in 1982 from four seed-bearing trees sourced from wild stock of a northern Michigan relict population. This grove of trees has dispersed over an area up to 370 meters from the parent trees. The trees appear to be free of chestnut blight.{{cite journal |last1=Mazurowski |first1=Jason |last2=Heinrich |first2=Bernd |last3=Heinrich |first3=Lena |last4=Loeb |first4=Carolyn |last5=Rives |first5=Robert |title=The Continued Spread of a Wild Population of American Chestnuts |journal=Northeastern Naturalist |date=20 July 2022 |volume=29 |issue=3 |doi=10.1656/045.029.0302|s2cid=250936749 }} The University of Maine Foundation believes it has the tallest chestnut in North America on its property in Lovell, Maine. As per a 2015 measurement, it was {{convert|115|ft}} tall, {{convert|16|in}} in girth and believed to be around 100 years old.{{Cite web |date=2015-12-03 |title=Tallest American Chestnut Tree Found In Maine |url=https://www.mainepublic.org/environment-and-outdoors/2015-12-03/tallest-american-chestnut-tree-found-in-maine |access-date=2023-12-26 |website=Maine Public |language=en}}{{Cite web |last=Hashey |first=Monique |date=2016-02-17 |title=Tallest American chestnut tree in North America discovered on Foundation property |url=https://umainefoundation.org/tallest-american-chesnut-tree-in-north-america-discovered-on-foundation-property/ |access-date=2023-12-26 |website=University of Maine Foundation |language=en-US}}
• Two of the largest surviving trees are in Jackson County, Tennessee. One, the state champion, has a diameter of {{convert|61|cm|in|0|abbr=on}} and a height of {{convert|23|m|ft|0|abbr=on}}, and the other tree is nearly as large. One of them has been pollinated with hybrid pollen by members of The American Chestnut Foundation; the progeny will have mostly American chestnut genes and some will be blight resistant.
• A stand of several trees near Warm Springs, Georgia, has a tree that is approximately 20–30 years old and {{convert|13|m|ft|0|abbr=on}} tall and is the southernmost American chestnut tree known to be flowering and producing nuts.Minor, Elliott. [https://www.washingtonpost.com/wp-dyn/content/article/2006/05/19/AR2006051901548.html "Rare American Chestnut Trees Discovered"]. The Washington Post, May 19, 2006. Retrieved September 23, 2015.Merkle, Scott A. [http://www.georgiaencyclopedia.org/articles/geography-environment/american-chestnut "American Chestnut"]. New Georgia Encyclopedia, February 11, 2015. Retrieved September 23, 2015.
• A large tree was found in Talladega National Forest, Alabama, in 2005.Spencer, Thomas. [http://blog.al.com/spotnews/2010/12/seeds_of_hope_for_american_che.html "Seeds of hope arise for American Chestnuts, head of Alabama chapter of American Chestnut Foundation says"]. The Birmingham News, December 4, 2010. www.blog.al.com. Retrieved September 23, 2015.
• In 2007 a stand of trees was discovered near the northeastern Ohio town of Braceville.[https://news.google.com/newspapers?nid=799&dat=20070827&id=54NaAAAAIBAJ&sjid=wUkDAAAAIBAJ&pg=3203,6271855&hl=en "Stand of Chestnut Trees Defying Odds"]. The Bryan Times, August 27, 2007. Google News. Retrieved September 23, 2015.{{cite news |last=Haddon |first=Heather |url=https://www.wsj.com/articles/SB10000872396390444233104577593571278706402 |title=Hopes for a Chestnut Revival Growing |work=The Wall Street Journal |date=August 19, 2012 |access-date=September 23, 2015 }} The stand encompasses four large flowering trees, the largest of which is about {{convert|23|m|ft|0|abbr=on}} tall, sited among hundreds of smaller trees that have not begun to flower, located in and around a sandstone quarry. A combination of factors may account for the survival of these relatively large trees, including low levels of blight susceptibility, hypovirulence, and good site conditions. In particular, some stands may have avoided exposure due to being located at a higher altitude than blighted trees in the neighboring area; the fungal spores are not carried to higher altitudes as easily.
• In 2008, officials of the Ohio Department of Natural Resources announced a rare adult American chestnut tree had been discovered in a marsh near Lake Erie. The officials admitted they had known about the tree for seven years but had kept its existence a secret. The exact location of the tree is still being held secret, both because of the risk of infecting the tree and because an eagle had nested in its branches. They described the tree as being {{convert|89|ft}} tall and having a circumference of {{convert|5|ft}}. The American Chestnut Foundation was also only recently told about the tree's existence.[http://www.ohio.com/news/top-stories/rare-american-chestnut-tree-discovered-in-sandusky-marsh-1.94039 "Rare American chestnut tree discovered in Sandusky marsh"]. Akron Beacon Journal, June 17, 2011. Retrieved September 25, 2015.
• Members of the Kentucky chapter of the American Chestnut Foundation have been pollinating a tree found on a farm in Adair County, and a specimen found on Henderson Ridge in Elliott County. The Adair County tree is over one hundred years old.{{cite web |url=http://www.columbiamagazine.com/index.php?sid=12051 |title=State's largest historic Chestnut tree stands on an Adair County farm |work=Columbia Magazine |date=June 17, 2005 |access-date=October 5, 2015 }}Flavell, John. [http://www.dailyindependent.com/news/local_news/american-tale-bringing-back-the-perfect-tree/article_1f44ba9a-166d-5a44-adb8-9e7df0468811.html "American tale: Bringing back the perfect tree"]. www.dailyindependent.com, July 24, 2009.
• In 2007 a mature American chestnut was discovered in Farmington, New Hampshire.Ramsdell, Laurenne. [http://www.fosters.com/article/20130721/GJNEWS_01/130729869 "Farmington chestnut tree may have saved species"]. www.fosters.com, July 21, 2013. Retrieved September 25, 2015.
• In rural Missaukee County, Michigan, a blight-free grove of American chestnut trees approximately {{convert|0.33|acre}} in size with the largest tree measuring {{convert|128|in|cm|abbr=on}} in circumference ({{convert|40|in|cm|abbr=on}} diameter) has been located. It is believed to be the result of nuts planted by early settlers in the area. The American Chestnut Council has verified its identity and existence. Efforts have been initiated to protect the property from logging and development.{{Citation needed|date=October 2009}} In Lansing, Michigan, Fenner Nature Center is home to a grove of blight-free American chestnuts descended from the grove in Missaukee County.Hull, Christopher. [http://www.mynaturecenter.org/Resources/Documents/The%20American%20Chestnut%20Project%20at%20Fenner%20Nature%20Center,%20Full%20Version%2012-16-10.pdf "The American Chestnut Project at Fenner Nature Center"] {{Webarchive|url=https://web.archive.org/web/20140517122106/http://www.mynaturecenter.org/Resources/Documents/The%20American%20Chestnut%20Project%20at%20Fenner%20Nature%20Center,%20Full%20Version%2012-16-10.pdf |date=May 17, 2014 }}. www.mynaturecenter.org. Retrieved September 23, 2015.
• American chestnuts have been located on Beaver Island in Lake Michigan.Whately, Cathryn Elizabeth, Daniel E. Wujek and Edwin E. Leuck II. [http://hdl.handle.net/2027/spo.0497763.0044.107 "The Vascular Flora of Hog Island, Charlevoix County, Michigan"]. The Michigan Botanist 44.1 (Winter, 2005): 29-48. University of Michigan Library Digital Collections. Retrieved October 29, 2015.
• Hundreds of healthy American chestnuts have been found in the proposed Chestnut Ridge Wilderness Area in the Allegheny National Forest in northwestern Pennsylvania.Friends of Allegheny Wilderness. [http://www.pawild.org/pdfs/CitizensWildProp.pdf "A Citizens' Wilderness Proposal for Pennsylvania's Allegheny National Forest"]. Friends of Allegheny Wilderness, 2003. www.pawild.org. Retrieved October 4, 2015. Many of these trees measure more than {{convert|60|ft|abbr=on}} in height. These trees will be protected from logging if the wilderness area, proposed by Friends of Allegheny Wilderness, is passed into law.
• The Montreal Botanical Garden has the American chestnut among its collection of trees and ornamental shrubs.{{cite web|title=Trees and Ornamental Shrubs: American chestnut [English page]|url=http://espacepourlavie.ca/en/green-pages/american-chestnut|work=Montreal Botanical Garden|publisher=Space for Life Montreal|access-date=July 6, 2013|archive-date=August 4, 2014|archive-url=https://web.archive.org/web/20140804201628/http://espacepourlavie.ca/en/green-pages/american-chestnut}}
• Three of Portland, Oregon's heritage trees are American chestnuts, along with three Spanish (European) chestnuts.{{cite web |url=http://www.portlandoregon.gov/parks/article/477139? |title=Castanea dentata |website=Portland Parks and Recreation |access-date=July 19, 2019}}{{failed verification|reason=The webpage lists only one specimen of American chestnut, and does not mention Spanish chestnuts.|date=July 2019}}
• At least two American chestnuts live on the side of Skitchewaug Trail in Springfield, Vermont.Smallheer, Susan. [http://www.rutlandherald.com/article/20090718/NEWS04/907180356 "Couple works to save ailing American chestnut tree"] {{Webarchive|url=https://web.archive.org/web/20141015205640/http://www.rutlandherald.com/article/20090718/NEWS04/907180356 |date=October 15, 2014 }}. Rutland Herald, July 18, 2009. Retrieved May 31, 2014.
• Around 300 to 500 trees were spotted in the George Washington National Forest near Augusta County, Virginia, in 2014. Over one dozen trees were at least 12 inches in diameter with several measuring nearly 24 inches in diameter. Only one of the larger trees was a seed and pollen producer with numerous pods and pollen strands lying on ground. The site did, however, have a high presence of chestnut blight, although the seed producing tree and several other large ones were relatively blight-free with minimal to no damage.
• Two trees were planted 1985, in Nova Scotia, at Dalhousie University, Sexton Campus and are thriving. The donated trees were from saplings grown in Europe, away from the blight. They have {{convert|16|in|cm|adj=on}} diameter trunks and are approximately {{convert|40|ft}} high.
• A single mature American chestnut can be found on the front lawn of the McPhail house heritage site in Sault Ste Marie, Ontario, planted by former mayor John Alexander McPhail in the 1920s. Well north of the natural range of the chestnut, it has avoided the blight.{{cite news|last1=Della-Mattia|first1=Elaine|title=McPhail house registered as heritage home|url=http://www.saultstar.com/2011/04/04/mcphail-house-registered-as-heritage-home|access-date=May 25, 2017|work=Sault Star|date=April 5, 2011}}{{Dead link|date=September 2019 |bot=InternetArchiveBot |fix-attempted=yes }}
• There is one tree in South Centre Township, Pennsylvania. It is a hardy, nut-producing tree that has been producing for nearly 30 years.
• A solitary tree exists in Wawayanda, New York, planted in the early 1990s as part of a local soil and water conservation district program to identify blight/resistant specimens. It has borne fruit since 2005.
• A lone tree grows on the Oakdale Campus in Coralville, Iowa.[https://now.uiowa.edu/2016/10/tree-freak]. "Iowa now, Tree Freak" Retrieved June 24, 2019.
• The great majority of chestnut trees in the United States are derived from Dunstan chestnuts, developed in Greensboro, North Carolina, in the 1960s.[https://chestnuthilltreefarm.com/learning-center/dunstan-chestnut-history-2/ "Dunstan chestnut trees"]. www.chestnuthilltreefarm.com.. Retrieved September 02, 2020
• The Canadian Chestnut Council has a plot growing and harvesting chestnut trees at Tim Hortons Children's Foundation Onondaga Farms. The seedlings are grown at a Simcoe station. They are then brought in the spring to this test plantation in St. George, Ontario.{{Cite web|url=https://www.canadianchestnutcouncil.ca/index.cfm?page=home|title=Canadian Chestnut Council|website=www.canadianchestnutcouncil.ca}}{{Cite web|url=https://news.uoguelph.ca/2012/06/crossbreeding-aims-to-save-chestnut-trees/|title=Crossbreeding Aims to Save Chestnut Trees|date=June 13, 2012}} {{better source needed|date=July 2019}}
• Multiple nut-bearing trees are in Wind River Arboretum, Washington.

File:1998.105.157 bw-General Use.jpg (American, 1836–1910). Chestnutting, 1870. Wood engraving, Sheet: {{frac|11|3|4}} × {{frac|8|3|4}} in. (29.8 × 22.2 cm). Brooklyn Museum, Gift of Harvey Isbitts, 1998.105.157]]

The nuts were once an important economic resource in North America, being sold on the streets of towns and cities, as they sometimes still are during the Christmas season (usually said to be "roasting on an open fire" because their smell is readily identifiable many blocks away). Chestnuts are edible raw or roasted, though typically preferred roasted. One must peel the brown skin to access the yellowish-white edible portion.

The nuts were commonly fed on by various types of wildlife and was also in such a high abundance that they were used to feed livestock by farmers, by allowing those livestock to roam freely into the forests that were predominantly filled with American chestnut trees. The tree was important to many Native American tribes in North America as it served as a food source, both for them and the wildlife they hunted,{{Cite web|last=Schlarbaum|first=Scott|date=1998|title=Three American Tragedies: Chestnut Blight, Butternut Canker, and Dutch Elm Disease|url=https://www.nrs.fs.fed.us/pubs/jrnl/1998/1998_exotic-pests-papers/schlarbaum_1998-exoticpests.pdf|website=Forest Service Northern Research Station|access-date=April 20, 2020|archive-date=September 25, 2020|archive-url=https://web.archive.org/web/20200925134828/https://www.nrs.fs.fed.us/pubs/jrnl/1998/1998_exotic-pests-papers/schlarbaum_1998-exoticpests.pdf}} and also as a component in traditional medicine.

The January 1888 issue of Orchard and Garden mentions the American chestnut as being "superior in quality to any found in Europe".Fuller, A. S. [https://books.google.com/books?id=pylOAAAAYAAJ&dq=american+chestnut+Snowline+Orchard&pg=PA4 "Nuts & Nut Trees"]. Orchard and Garden, 10 (January 1888): 5. Little Silver, New Jersey: J.T. Lovett. via Google Books. Retrieved June 6, 2014. The wood is straight-grained, strong, and easy to saw and split, and it lacks the radial end grain found on most other hardwoods. The tree was particularly valuable commercially since it grew at a faster rate than oaks. Being rich in tannins, the wood was highly resistant to decay and therefore used for a variety of purposes, including furniture, split-rail fences, shingles, home construction, flooring, piers, plywood, paper pulp, and telephone poles. Tannins were also extracted from the bark for tanning leather. Although larger trees are no longer available for milling, much chestnut wood has been reclaimed from historic barns to be refashioned into furniture and other items.[http://www.tappanchairs.com/the-american-chestnut-foundation-chair.html "The American Chestnut Foundation Chair"]. {{webarchive |url=https://web.archive.org/web/20151001124503/http://www.tappanchairs.com/the-american-chestnut-foundation-chair.html |date=October 1, 2015}} www.tappanchairs.com. Retrieved September 24, 2015.

"Wormy" chestnut refers to a defective grade of wood that has insect damage, having been sawn from long-dead, blight-killed trees. This "wormy" wood has since become fashionable for its rustic character.{{Cite web |title=Wormy Chestnut |url=http://www.wood-database.com/lumber-identification/hardwoods/wormy-chestnut/ |archive-url=https://web.archive.org/web/20150926013509/http://www.wood-database.com/lumber-identification/hardwoods/wormy-chestnut/ |archive-date=26 September 2015 |access-date=25 September 2015 |website=www.wood-database.com}}{{Cite web |title=Antique Wormy Chestnut Lumber |url=https://www.appalachianwoods.com/reclaimed-lumber-and-timbers/reclaimed-lumber/antique-wormy-chestnut-lumber/ |access-date=25 September 2015 |website=Appalachian Woods, LLC |language=en-US}}

• Central and southern Appalachian montane oak forest
• Ozark Chinquapin Foundation

{{Reflist|refs=

{{cite web|title=Castanea × neglecta Dode|url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:49294-2|website=Plants of the World Online|publisher=Royal Botanical Gardens Kew |access-date=12 August 2020}}

}}

{{Commons category|Castanea dentata}}

• [https://tacf.org/ The American Chestnut Foundation]
• [http://www.accf-online.org/ American Chestnut Cooperators Foundation]
• [https://canadianchestnutcouncil.ca/ Canadian Chestnut Council]
• [https://www.esf.edu/chestnut/ American Chestnut Research and Restoration Center, SUNY-ESF]
• {{YouTube|0SLJelHD8Ik|title=Rise and Fall of the American Chestnut: Whately Mass. Historical Society}}
• {{inaturalist taxon|49186}}

{{Taxonbar|from=Q468698}}

Category:Castanea

Category:Trees of Northern America

Category:Edible nuts and seeds

Category:Hardwood forest plants

Category:Native American cuisine

Category:Ark of Taste foods