Rock Elm
Encyclopedia
Ulmus thomasii, the Rock Elm or Cork Elm, 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
. Its preferred habitat is moist but well-drained sandy loam, loam, or silt loam soil, mixed with other hardwood
s; it is moderately shade-tolerant. However, it also grows on dry uplands, especially on rocky ridges and limestone
bluffs.
, who had first named and described the tree in 1831 as Ulmus racemosa.
. The 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.
The leaves
are 5 – 10 cm long and 2 – 5 cm wide, oval
to obovate
with a round, symmetrical base and acuminate apex. The leaf surface is shiny dark green, turning bright yellow in autumn; the underside is pubescent. The perfect apetalous, wind pollinated flower
s are red-green and appear in racemes < 40 mm long two weeks before the leaves from March to May, depending on the tree's location. The fruit
is a broad ovate samara
13 – 25 mm long covered with fine hair, notched at the tip, and maturing during May or June to form drooping clusters at the leaf bases.
Although U. thomasii is protandrous, levels of self-pollination remain high.
s. However, it also grows on dry uplands, especially on rocky ridges and limestone
bluffs.
.
s of Ulmus thomasii, nor is it known to be in commerce. The species is occasionally grown beyond its native range as a specimen tree in botanical garden
s and arboreta
, for example in northwestern Europe
, but not commonly cultivated in northern Europe, being unsuited to the region's more temperate, maritime climate.
Ulmus thomasii was crossed experimentally with Japanese Elm (Ulmus davidiana var. japonica) at the Arnold Arboretum in Massachusetts
, but no clones were released to commerce. Seedlings arising from crossings with Siberian elm (U. pumila) at the Lake States Forestry Experimental Station in the 1950s all perished, a classic case of hybrid lethality
..
Europe
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 shipbuilding
, furniture
, 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 < 2 mm a year. Over 250 annual growth rings were once counted in a log 24 cm square being sawn for gunwale
s in an English boatyard, while a tree once grown at Kew Gardens, London
, attained a height of only 12 m in 50 years.
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
tree native primarily to the Midwestern United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. The tree ranges from southern Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
and Quebec
Quebec
Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
, south to Tennessee
Tennessee
Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...
, west to northeastern Kansas
Kansas
Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...
, and north to Minnesota
Minnesota
Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...
. Its preferred habitat is moist but well-drained sandy loam, loam, or silt loam soil, mixed with other hardwood
Hardwood
Hardwood is wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood...
s; it is moderately shade-tolerant. However, it also grows on dry uplands, especially on rocky ridges and limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
bluffs.
Etymology
The tree was named in 1902 for David Thomas, an American civil engineerCivil engineer
A civil engineer is a person who practices civil engineering; the application of planning, designing, constructing, maintaining, and operating infrastructures while protecting the public and environmental health, as well as improving existing infrastructures that have been neglected.Originally, a...
, who had first named and described the tree in 1831 as Ulmus racemosa.
Description
Ulmus thomasii grows as a tree from 50-100 feet (15–30 m) tall, and may live up to 300 years. Where forest-grown, the crown is cylindrical and upright with short branches, and is narrower than most other elms. Rock elm is also unusual among elms in that it is often monopodialMonopodial
Vascular plants with monopodial growth habits grow upward from a single point. They add leaves to the apex each year and the stem grows longer accordingly...
. The bark
Bark
Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term. It overlays the wood and consists of the inner bark and the outer bark. The inner...
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.
The leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
are 5 – 10 cm long and 2 – 5 cm wide, oval
Leaf shape
In botany, leaf shape is characterised with the following terms :* Acicular : Slender and pointed, needle-like* Acuminate : Tapering to a long point...
to obovate
Leaf shape
In botany, leaf shape is characterised with the following terms :* Acicular : Slender and pointed, needle-like* Acuminate : Tapering to a long point...
with a round, symmetrical base and acuminate apex. The leaf surface is shiny dark green, turning bright yellow in autumn; the underside is pubescent. The perfect apetalous, wind pollinated flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s are red-green and appear in racemes < 40 mm long two weeks before the leaves from March to May, depending on the tree's location. The fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
is a broad ovate samara
Samara (fruit)
A samara is a type of fruit in which a flattened wing of fibrous, papery tissue develops from the ovary wall. A samara is a simple dry fruit and indehiscent . It is a winged achene...
13 – 25 mm long covered with fine hair, notched at the tip, and maturing during May or June to form drooping clusters at the leaf bases.
Although U. thomasii is protandrous, levels of self-pollination remain high.
Ecology
Ulmus thomasii is moderately shade-tolerant. Its preferred habitat is moist but well-drained sandy loam, loam, or silt loam soil, mixed with other hardwoodHardwood
Hardwood is wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood...
s. However, it also grows on dry uplands, especially on rocky ridges and limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
bluffs.
Pests and diseases
Like most North American elms (Ulmus), U. thomasii is very susceptible to Dutch elm diseaseDutch elm disease
Dutch elm disease is a disease caused by a member of the sac fungi category, affecting elm trees which is spread by the elm bark beetle. Although believed to be originally native to Asia, the disease has been accidentally introduced into America and Europe, where it has devastated native...
.
Cultivation
There are no known cultivarCultivar
A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...
s of Ulmus thomasii, nor is it known to be in commerce. The species is occasionally grown beyond its native range as a specimen tree in botanical garden
Botanical garden
A botanical garden The terms botanic and botanical, and garden or gardens are used more-or-less interchangeably, although the word botanic is generally reserved for the earlier, more traditional gardens. is a well-tended area displaying a wide range of plants labelled with their botanical names...
s and arboreta
Arboretum
An arboretum in a narrow sense is a collection of trees only. Related collections include a fruticetum , and a viticetum, a collection of vines. More commonly, today, an arboretum is a botanical garden containing living collections of woody plants intended at least partly for scientific study...
, for example in northwestern Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, but not commonly cultivated in northern Europe, being unsuited to the region's more temperate, maritime climate.
Ulmus thomasii was crossed experimentally with Japanese Elm (Ulmus davidiana var. japonica) at the Arnold Arboretum in Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
, but no clones were released to commerce. Seedlings arising from crossings with Siberian elm (U. pumila) at the Lake States Forestry Experimental Station in the 1950s all perished, a classic case of hybrid lethality
Reproductive isolation
The mechanisms of reproductive isolation or hybridization barriers are a collection of mechanisms, behaviors and physiological processes that prevent the members of two different species that cross or mate from producing offspring, or which ensure that any offspring that may be produced is not...
..
Accessions
North America- Arnold Arboretum, MassachusettsMassachusettsThe Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
. Acc. no. 444-88. - Brenton ArboretumBrenton ArboretumThe Brenton Arboretum 121 acres is a new arboretum and botanical garden in early stages of development, located at 2629 Palo Circle, Dallas Center, Iowa, USA. The Arboretum aims to display all Iowa native trees and shrubs suitable to the site, as well as many other tree species which can grow in...
, Dallas Center, IowaIowaIowa is a state located in the Midwestern United States, an area often referred to as the "American Heartland". It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of the French colony of New...
. No acc. details available. - Dominion ArboretumDominion ArboretumThe Dominion Arboretum is located at the Central Experimental Farm of Agriculture and Agri-Food Canada in Ottawa, Ontario, Canada.Originally begun in 1889 the Arboretum covers about 26 ha of rolling land between Prince of Wales Drive, Dow's Lake and the Rideau Canal. Carleton University is located...
, OttawaOttawaOttawa is the capital of Canada, the second largest city in the Province of Ontario, and the fourth largest city in the country. The city is located on the south bank of the Ottawa River in the eastern portion of Southern Ontario...
, OntarioOntarioOntario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
, CanadaCanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. No acc. details. - Morton ArboretumMorton ArboretumThe Morton Arboretum, in Lisle, Illinois, covers 1,700 acres and is made up of gardens of various plant types and collections of trees from specific taxonomical and geographical areas. It includes native woodlands and a restored Illinois prairie. The Arboretum has over 4,100 different species of...
, IllinoisIllinoisIllinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...
. Acc. no. 178-84, wild collected from Reedsville, WisconsinReedsville, WisconsinReedsville is a village in Manitowoc County, Wisconsin, United States. The population was 1,187 at the 2000 census.-History:The village was named after Judge George Reed, who, with his partner, Jacob Lueps, bought a section of land in the town of Maple Grove, Wisconsin. In 1854, they had the land...
; 843-2005 (Kelleys IslandKelleys Island, OhioKelleys Island is both a village in Erie County, Ohio, United States, and the island which it fully occupies in Lake Erie. Originally known as Island Number 6 and later Cunningham Island, it was renamed in 1840 for brothers Datus and Irad Kelley, who were largely responsible for cultivatating the...
, Erie CountyErie County, OhioAs of the census of 2000, there were 79,551 people, 31,727 households, and 21,764 families residing in the county. The population density was 312 people per square mile . There were 35,909 housing units at an average density of 141 per square mile...
, OhioOhioOhio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...
); 122-2006 (Dixon County, NebraskaNebraskaNebraska is a state on the Great Plains of the Midwestern United States. The state's capital is Lincoln and its largest city is Omaha, on the Missouri River....
). - Nebraska Statewide ArboretumNebraska Statewide ArboretumThe Nebraska Statewide Arboretum is an arboretum and botanical garden composed of 44 arboretums, parks, and other public landscapes in 33 communities across Nebraska, and supported by the arboretum office at the University of Nebraska campus in Lincoln, Nebraska...
. No details available.
Europe
- Grange Farm ArboretumGrange Farm ArboretumThe Grange Farm Arboretum is a small private arboretum comprising 3 hectares accommodating over 800 trees, mostly native and ornamental species or cultivars, notably oaks, ashes, walnuts and elms, growing on a calcareous loam....
, Sutton St. James, SpaldingSpalding, LincolnshireSpalding is a market town with a population of 30,000 on the River Welland in the South Holland district of Lincolnshire, England. Little London is a hamlet directly south of Spalding on the B1172 road....
, Lincs. UK. Acc. no. 706. - National Botanic Garden of BelgiumNational Botanic Garden of BelgiumThe National Botanic Garden of Belgium is located in the grounds of Bouchout Castle near the village of Meise, just north of Brussels. It is one of the largest botanical gardens in the world with an extensive collection of living plants in addition to a herbarium of over 3 million specimens...
, MeiseMeiseMeise is a municipality located in the Belgian province of Flemish Brabant. The municipality comprises the towns of Meise proper and Wolvertem , and, several smaller villages like Sint-Brixius-Rode, Oppem, Meusegem, Impde/Imde, Rossem, Westrode and quarters as Bouchout, Nerom and Slozen. As of...
, BelgiumBelgiumBelgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
. Acc. no. 19800105. - National Botanic Gardens, Ireland, GlasnevinGlasnevinGlasnevin is a largely residential neighbourhood of Dublin, Ireland.-Geography:A mainly residential neighbourhood, it is located on the Northside of the city of Dublin . It was originally established on the northern bank of the River Tolka...
, Dublin, IrelandRepublic of IrelandIreland , described as the Republic of Ireland , is a sovereign state in Europe occupying approximately five-sixths of the island of the same name. Its capital is Dublin. Ireland, which had a population of 4.58 million in 2011, is a constitutional republic governed as a parliamentary democracy,...
. Location: A3 (155) - Wakehurst Place GardenWakehurst Place GardenWakehurst Place is National Trust property located near Ardingly, West Sussex in the High Weald of southern England , comprising a late 16th century country house and a mainly 20th century garden, managed by the Royal Botanic Gardens, Kew...
Wakehurst Place, UK. Acc. no. 1968-48603.
Other uses
The woodWood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
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 shipbuilding
Shipbuilding
Shipbuilding is the construction of ships and floating vessels. It normally takes place in a specialized facility known as a shipyard. Shipbuilders, also called shipwrights, follow a specialized occupation that traces its roots to before recorded history.Shipbuilding and ship repairs, both...
, furniture
Furniture
Furniture is the mass noun for the movable objects intended to support various human activities such as seating and sleeping in beds, to hold objects at a convenient height for work using horizontal surfaces above the ground, or to store things...
, agricultural tools
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
, and musical instrument
Musical instrument
A musical instrument is a device created or adapted for the purpose of making musical sounds. In principle, any object that produces sound can serve as a musical instrument—it is through purpose that the object becomes a musical instrument. The history of musical instruments dates back to the...
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 < 2 mm a year. Over 250 annual growth rings were once counted in a log 24 cm square being sawn for gunwale
Gunwale
The gunwale is a nautical term describing the top edge of the side of a boat.Wale is the same word as the skin injury, a wheal, which, too, forms a ridge. Originally the gunwale was the "Gun ridge" on a sailing warship. This represented the strengthening wale or structural band added to the design...
s in an English boatyard, while a tree once grown at Kew Gardens, London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
, attained a height of only 12 m in 50 years.