View source for Ulmus thomasii

{{Short description|Species of tree}}
{{Redirect|Rock Elm}}
{{Italic title}}
{{Speciesbox
| name = Rock elm
| image = Ulmus thomasii (meisse) 1.jpg
| image_caption = Rock elm, Meise.
| parent = Ulmus sect. Chaetoptelea
| display_parents = 2
| genus = Ulmus
| species = thomasii
| status = LC
| status_system = IUCN3.1
| status_ref = <ref name="iucn status 18 November 2021">{{cite iucn |author=Stritch, L. |date=2018 |title=''Ulmus thomasii'' |volume=2018 |page=e.T61967392A61967401 |doi=10.2305/IUCN.UK.2018-1.RLTS.T61967392A61967401.en |access-date=18 November 2021}}</ref>
| authority = [[Charles Sprague Sargent|Sarg.]]
| range_map = Ulmus thomasii range map 3.png
| range_map_caption = Natural range of ''Ulmus thomasii''
| synonyms =
* ''Ulmus racemosa'' <small>Thomas</small>
| synonyms_ref = <ref>{{Tropicos}}</ref>
}}

'''''Ulmus thomasii''''', the '''rock elm'''<ref name=BSBI07>{{BSBI 2007 |access-date=2014-10-17 }}</ref> or '''cork elm''' (or '''orme liège''' in [[Québec]]),  is a [[deciduous]] tree native primarily to the [[Midwestern United States]]. The tree ranges from southern [[Ontario]] and [[Quebec]], south to [[Tennessee]], west to northeastern [[Kansas]], and north to [[Minnesota]].<ref>{{cite web | url = http://esp.cr.usgs.gov/data/atlas/little/ulmuthom.pdf | title = Ulmus Thomasii Range Map | access-date = 2008-03-02 | publisher = [[United States Geological Survey]]}}</ref>

== Etymology ==
The tree was named in 1902 for David Thomas, an American [[civil engineer]] who had first named and described the tree in 1831 as ''Ulmus racemosa''.<ref>This name had been used in 1800 for a different species of elm, hence the need for the later renaming that honored Thomas.</ref>

== Description ==
''Ulmus thomasii'' grows as a tree from {{convert|15|–|30|m|ft|round=5|abbr=on}} tall, and may live for up to 300 years. Where forest-grown, the crown is cylindrical and upright with short branches, and is narrower than most other elms.<ref>Photographs of mature Rock Elm showing narrow profile: Virginia Tech Department of Forest Resources [http://dendro.cnre.vt.edu/dendrology/syllabus/factsheet.cfm?ID=135], Natural Resources of Canada, tidcf.nrcan.gc.ca [https://tidcf.nrcan.gc.ca/images_web/imfc/arbres/photos/moyen/ulmus_thomosii_04.jpg] {{Webarchive|url=https://web.archive.org/web/20160802233957/http://tidcf.nrcan.gc.ca/images_web/imfc/arbres/photos/moyen/ulmus_thomosii_04.jpg |date=2016-08-02 }} [https://tidcf.nrcan.gc.ca/trees/factsheet/369]</ref> Rock elm is also unusual among North American elms in that it is often [[monopodial]].<ref name=Bean>Bean, W. J. (1981). ''Trees and shrubs hardy in Great Britain'', 7th edition. Murray, London.</ref> The [[Bark (botany)|bark]] is grey-brown and deeply furrowed into scaly, flattened ridges. Many older branches have 3–4 irregular thick corky wings. It is for this reason the rock elm is sometimes called the cork elm.<ref>Photograph of corky ridges of Rock Elm branches, Michigan State University ''Plant Encyclopedia'' [http://www.saylorplants.com/images/Ulmus/Ulmusthom_AAL01_SilvicsNorthAmerica_AH-654.jpg]</ref>

The [[leaves]] are {{convert|5|–|10|cm|in|0|abbr=on}} long and {{convert|2|–|5|cm|in|frac=4|abbr=on}} wide, [[oval]] to [[obovate (botany)|obovate]] with a round, symmetrical base and acuminate apex.<ref>{{Naturalis Biodiversity Center |id=WAG.1846088 }} ''U. thomasii'' leaves specimen, Quebec, 1932; {{Naturalis Biodiversity Center |id=L.1582468 }}  ''U. thomasii'' leaves specimen, [[Arnold Arboretum]], 1960</ref> The leaf surface is shiny dark green, turning bright yellow in autumn; the underside is [[pubescent (botany)|pubescent]]. The [[perfect flower|perfect]] [[apetalous]], [[wind-pollinated]] [[flower]]s are red-green and appear in racemes up to {{convert|40|mm|in|0|abbr=on}} long two weeks before the leaves from March to May, depending on the tree's location. The [[fruit]] is a broad ovate [[Samara (fruit)|samara]] {{convert|13|–|25|mm|in|frac=32|abbr=on}} long covered with fine hair, notched at the tip, and maturing during May or June to form drooping clusters at the leaf bases.<ref name=White>White, J & More, D. (2003). ''Trees of Britain & Northern Europe''. Cassell's, London.</ref>

Although ''U. thomasii'' is [[protandrous]], levels of self-pollination remain high.<ref name="Hans">{{cite journal|last=Hans|first=A. S.|year=1981|title=Compatibility and Crossability Studies in Ulmus|journal=Silvae Genetica|volume= 30|pages=4–5}}</ref>

<gallery>
File:The North American sylva; or, A description of the forest trees of the United States, Canada and Nova Scotia. Considered particularly with respect to their use in the arts and their introduction into (14778570501).jpg|''U. racemosa'' [:''U. thomasii''] diagnostic illustration (1865)
File:A guide to the trees (Page 123) (8434849285).jpg|''U. racemosa'' [:''U. thomasii''] diagnostic illustration (1900)
File:The tree book - A popular guide to a knowledge of the trees of North America and to their uses and cultivation (1920) (14782984355).jpg|''U. thomasii'' shoot and buds (1920)
File:Ulmus thomasii (meisse) leaves 2.jpg|''U. thomasii'' new leaves, Meisse
File:UlmusThomasii10.jpg|''U. thomasii'' August leaves on short shoot, [[Jamesville, New York]]
File:SHHG Rock Elm leaf.jpg|''U. thomasii'' leaves, Sir Harold Hillier Gardens, England
File:Ulmus thomasii (meisse) bark.jpg|''U. thomasii'' bark, Meisse
File:UlmusThomasii17.jpg|''U. thomasii'' young bark
File:Ulmus thomasii (meisse) corky wings.jpg|''U. thomasii'' corky twig, Meisse
</gallery>

== Ecology ==
''Ulmus thomasii'' is moderately shade-tolerant.<ref>{{Cite web | url=http://forestry.about.com/library/silvics/blsilulmtho.htm | title=Forestry}}</ref> Its preferred habitat is moist but well-drained sandy loam, loam, or silt loam soil, mixed with other [[hardwood]]s. However, it also grows on dry uplands, especially on rocky ridges and [[limestone]] bluffs.

== Pests and diseases ==
Like most North American [[elm]]s, ''U. thomasii'' is very susceptible to [[Dutch elm disease]].

== Cultivation ==
There are no known [[cultivar]]s of ''Ulmus thomasii'', nor is it known to be any longer in commerce. It appeared in some US nursery catalogues in the early 20th century.<ref>[https://archive.org/details/CAT31287811/page/20 Kelsey, Frederick W., ''Choice Trees'', cat. 55, N.Y. 1906, p.20]</ref><ref>[https://archive.org/details/CAT31330100/page/28/mode/2up Griffing's tree & plant book, 1929; Griffing's Interstate Nurseries, C.M. Griffing & Company;p.29]</ref><ref>[https://archive.org/details/CAT31332851/page/20/mode/2up Griffing's tree & plant book, 1930; Griffing's Interstate Nurseries; p 20]</ref> It has, however, been planted as a street tree in [[Cheyenne, Wyoming]], where in tight lines it keeps a monopodial habit recalling [[Ulmus minor 'Sarniensis'|Jersey elm]].<ref>[https://plantnebraska.org/file_download/inline/42abc7e4-83d0-4273-bdbd-4cc25aae24fd Justin Evertson, 'The Value of Large Trees', ''The Seed'', Spring 2007, p.6, Nebraska Statewide Arboretum]</ref> The species is occasionally grown beyond its native range as a specimen tree in [[botanical garden]]s and [[arboretum|arboreta]], for example in northwestern Europe, but not commonly cultivated in northern Europe, being unsuited to the region's more temperate, maritime climate. However, the tree was propagated and marketed in the UK by the Hillier & Sons nursery, [[Winchester, Hampshire]], from 1965 to 1977, during which time 49 were sold.<ref name="Hillier,a">Hillier & Sons (1977). ''Catalogue of Trees & Shrubs''. Hillier, Ampfield, UK.</ref><ref name="Hillier,b">Hillier & Sons ''Sales inventory 1962 to 1977'' (unpublished).</ref>

''Ulmus thomasii'' was crossed experimentally with [[Ulmus davidiana var. japonica|Japanese elm]] (''U. davidiana'' var. ''japonica'') at the [[Arnold Arboretum]] in [[Massachusetts]], but no clones were released to commerce.<ref name=Hans /> Seedlings arising from crossings with [[Siberian elm]] (''U. pumila'') at the Lake States Forestry Experimental Station in the 1950s all perished,<ref name=Sholtz>Sholtz, H. F. (1957). Rock Elm (Ulmus thomasii). ''Lake States Forest Experimental Station Paper'' 47:16.</ref> a classic case of [[reproductive isolation|hybrid lethality]].<ref>{{Cite journal |doi = 10.1104/pp.006023|pmid = 12481061|pmc = 166689|title = Cell Death Processes during Expression of Hybrid Lethality in Interspecific F1 Hybrid between Nicotiana gossei Domin and Nicotiana tabacum|journal = Plant Physiology|volume = 130|issue = 4|pages = 1776–1787|year = 2002|last1 = Mino|first1 = Masanobu|last2 = Maekawa|first2 = Kenji|last3 = Ogawa|first3 = Ken'Ichi|last4 = Yamagishi|first4 = Hiroshi|last5 = Inoue|first5 = Masayoshi}}</ref>

== Notable trees ==
The US National Champion, measuring {{convert|100|ft|m|abbr=on}} high in 1989, grows in [[Cass County, Michigan]].<ref name=American>{{cite web |publisher=American Forests |date=2012 |work=The 2012 National Register of Big Trees |title=Rock Elm (Ulmus thomasii) |url=http://www.americanforests.org/bigtree/rock-elm-ulmus-thomasii-3/}}</ref>

== Uses ==
The [[wood]] of the rock elm is the hardest and heaviest of all elms, and where forest-grown remains comparatively free of knots and other defects. It is also very strong and takes a high polish, and consequently was once in great demand in America and Europe for a wide range of uses, notably [[boatbuilding]], [[furniture]], [[agriculture|agricultural tools]], and [[musical instrument]]s.

Much of the timber's strength is derived from the tight grain arising from the tree's very slow rate of growth, the trunk typically increasing in diameter by less than {{convert|2|mm|in|frac=32|abbr=on}} a year. Over 250 annual growth rings were once counted in a log {{convert|24|cm|in|frac=4|abbr=on}} square being sawn for [[gunwale]]s in an English boatyard, while a tree once grown at [[Kew Gardens]], [[London]], attained a height of only {{convert|12|m|ft|abbr=on}} in 50 years.<ref name=Elwes>Elwes, H. J. & Henry, A. (1913). ''[http://fax.libs.uga.edu/QK488xE4/1f/trees_of_britain_and_ireland_vol_7.pdf The Trees of Great Britain & Ireland]''. Vol. VII. 1848–1929. Republished 2004 Cambridge University Press, {{ISBN|978-1-108-06938-0}}</ref>

== Accessions ==
;North America
*[[Arnold Arboretum]], [[Massachusetts]], US. Acc. no. 444-88.
*[[Brenton Arboretum]], [[Dallas Center]], [[Iowa]], US. No acc. details available.
*[[Dominion Arboretum]], [[Ottawa]], Canada. No acc. details.
*[[Morton Arboretum]], [[Illinois]], US. Acc. no. 178-84, wild collected from [[Reedsville, Wisconsin]]; 843-2005 ([[Kelleys Island, Ohio|Kelleys Island]], [[Erie County, Ohio|Erie County]], [[Ohio]]); 122-2006 ([[Dixon County]], [[Nebraska]]).
*[[Nebraska Statewide Arboretum]], US. No details available.
;Europe
*[[Grange Farm Arboretum]], [[Lincolnshire]], UK. Acc. no. 706.
*[[National Botanic Garden of Belgium]], [[Meise]], Belgium. Acc. no. 19800105.
*[[National Botanic Gardens (Ireland)|National Botanic Gardens, Ireland]],<ref>{{Cite web | url=http://www.botanicgardens.ie |title = The National Botanic Gardens of Ireland}}</ref> [[Glasnevin]], Ireland. Location: A3 (155)
*[[Sir Harold Hillier Gardens]], [[Hampshire]], UK.  Acc. no. 2008.0419, wild collected in Ontario, Canada, by Kristl Walek
*[[Wakehurst Place Garden]] [[Wakehurst Place]], UK. Acc. no. 1968-48603.

== References ==
{{Commons category}}
{{Reflist}}

==External links==
*[http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233501331 ''U. thomasii'', Flora of North America, www.efloras.org]
*[https://arboretum.harvard.edu/stories/ulmus-thomasii-the-hard-elm-thats-hard-to-find/ Brian Pruka, ''Ulmus thomasii'': 'The Hard Elm That's Hard to Find', ''Arnoldia'', Volume 74, Issue 1, 2016]

{{Elm species, varieties, hybrids, hybrid cultivars and species cultivars |state=collapsed}}
{{Taxonbar|from=Q1147786}}

[[Category:Ulmus|thomasii]]
[[Category:Trees of Northern America]]
[[Category:Ulmus articles with images]]
[[Category:Elm species and varieties]]