Elm

There are about 30 to 40 species of Ulmus (elm); the ambiguity in number results from difficulty in delineating species, owing to the ease of hybridization between them and the development of local seed-sterile vegetatively propagated microspecies in some areas, mainly in the field elm (Ulmus minor) group. Oliver Rackham[4] describes Ulmus as the most critical genus in the entire British flora, adding that 'species and varieties are a distinction in the human mind rather than a measured degree of genetic variation'. Eight species are endemic to North America and three to Europe, but the greatest diversity is in Asia with approximately two dozen species.[3]

The classification adopted in the List of elm species, varieties, cultivars and hybrids is largely based on that established by Brummitt.[5] A large number of synonyms have accumulated over the last three centuries; their currently accepted names can be found in the list List of elm Synonyms and Accepted Names.

Botanists who study elms and argue over elm identification and classification are called pteleologists, from the Greek πτελέα (:elm).[6]

As part of the sub-order urticalean rosids they are distant cousins of cannabis, hops, and nettles.

The genus is hermaphroditic, having apetalous perfect flowers which are wind-pollinated. Elm leaves are alternate, with simple, single- or, most commonly, doubly serrate margins, usually asymmetric at the base and acuminate at the apex. The fruit is a round wind-dispersed samara flushed with chlorophyll, facilitating photosynthesis before the leaves emerge.[8] The samarae are very light, those of British elms numbering around 50,000 to the pound (454 g).[9] All species are tolerant of a wide range of soils and pH levels but, with few exceptions, demand good drainage. The elm tree can grow to great height, often with a forked trunk creating a vase profile.

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  'Sapporo Autumn Gold', Antella, Florence
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  Wych elm (Ulmus glabra) leaves and seeds
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  Asymmetry of leaf, Slippery Elm U. rubra
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  Mature bark, Slippery Elm U. rubra
• 
  Flowers of the hybrid elm cultivar 'Columella'
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  Corky wings, Winged Elm U. alata
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  U. laciniata samara
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  U. americana, Dufferin St., Toronto, c. 1914

Camperdown elm (Ulmus 'Camperdown'), cultivated in Prospect Park, Brooklyn, New York

An avenue of elm trees in Fitzroy Gardens, Melbourne

One of the earliest of ornamental elms was the ball-headed graft narvan elm, Ulmus minor 'Umbraculifera', cultivated from time immemorial in Persia as a shade tree and widely planted in cities through much of south-west and central Asia. From the 18th century to the early 20th century, elms, whether species, hybrids or cultivars, were among the most widely planted ornamental trees in both Europe and North America. They were particularly popular as a street tree in avenue plantings in towns and cities, creating high-tunnelled effects. Their quick growth and variety of foliage and forms,[35] their tolerance of air-pollution and the comparatively rapid decomposition of their leaf-litter in the fall were further advantages.

In North America, the species most commonly planted was the American elm (Ulmus americana), which had unique properties that made it ideal for such use: rapid growth, adaptation to a broad range of climates and soils, strong wood, resistance to wind damage, and vase-like growth habit requiring minimal pruning. In Europe, the wych elm (Ulmus glabra) and the field elm (Ulmus minor) were the most widely planted in the countryside, the former in northern areas including Scandinavia and northern Britain, the latter further south. The hybrid between these two, Dutch elm (U. × hollandica), occurs naturally and was also commonly planted. In much of England, it was the English elm which later came to dominate the horticultural landscape. Most commonly planted in hedgerows, it sometimes occurred in densities of over 1000 per square kilometre. In south-eastern Australia and New Zealand, large numbers of English and Dutch elms, as well as other species and cultivars, were planted as ornamentals following their introduction in the 19th century, while in northern Japan Japanese Elm (Ulmus davidiana var. japonica) was widely planted as a street tree. From about 1850 to 1920, the most prized small ornamental elm in parks and gardens was the Camperdown elm (Ulmus glabra 'Camperdownii'), a contorted weeping cultivar of the Wych Elm grafted on to a non-weeping elm trunk to give a wide, spreading and weeping fountain shape in large garden spaces.

In northern Europe elms were, moreover, among the few trees tolerant of saline deposits from sea spray, which can cause "salt-burning" and die-back. This tolerance made elms reliable both as shelterbelt trees exposed to sea wind, in particular along the coastlines of southern and western Britain[36][37] and in the Low Countries, and as trees for coastal towns and cities.[38]

This belle époque lasted until the First World War, when as a consequence of hostilities, notably in Germany whence at least 40 cultivars originated, and of the outbreak at about the same time of the early strain of Dutch elm disease, Ophiostoma ulmi, the elm began its slide into horticultural decline. The devastation caused by the Second World War, and the demise in 1944 of the huge Späth nursery in Berlin, only accelerated the process. The outbreak of the new, three times more virulent, strain of Dutch elm disease Ophiostoma novo-ulmi in the late 1960s brought the tree to its nadir.

Since circa 1990 the elm has enjoyed a renaissance through the successful development in North America and Europe of cultivars highly resistant to DED.[8] Consequently, the total number of named cultivars, ancient and modern, now exceeds 300, although many of the older clones, possibly over 120, have been lost to cultivation. Some of the latter, however, were by today's standards inadequately described or illustrated before the pandemic, and it is possible that a number survive, or have regenerated, unrecognised. Enthusiasm for the newer clones often remains low owing to the poor performance of earlier, supposedly disease-resistant Dutch trees released in the 1960s and 1970s. In the Netherlands, sales of elm cultivars slumped from over 56,000 in 1989 to just 6,800 in 2004,[39] whilst in the UK, only four of the new American and European releases were commercially available in 2008.

Central Park

American elm trees along The Mall and Literary Walk in New York City's Central Park (2013)

New York City's Central Park is home to approximately 1,200 American elm trees, which constitute over half of all trees in the park. The oldest of these elms were planted during the 1860s by Frederick Law Olmsted, making them among the oldest stands of American elms in the world. The trees are particularly noteworthy along the Mall and Literary Walk, where four lines of American elms stretch over the walkway forming a cathedral-like covering. A part of New York City's urban ecology, the elms improve air and water quality, reduce erosion and flooding, and decrease air temperatures during warm days.[40]

While the stand is still vulnerable to DED, in the 1980s the Central Park Conservancy undertook aggressive countermeasures such as heavy pruning and removal of extensively diseased trees. These efforts have largely been successful in saving the majority of the trees, although several are still lost each year. Younger American elms that have been planted in Central Park since the outbreak are of the DED-resistant 'Princeton' and 'Valley Forge' cultivars.[41]

National Mall

Rows of American elm trees line a path south of the Lincoln Memorial Reflecting Pool on the National Mall in Washington, D.C. (November 11, 2006)

Several rows of American elm trees that the National Park Service (NPS) first planted during the 1930s line much of the 1.9 miles (3.0 km) length of the National Mall in Washington, D.C. DED first appeared on the trees during the 1950s and reached a peak in the 1970s. The NPS used a number of methods to control the epidemic, including sanitation, pruning, injecting trees with fungicide and replanting with DED-resistant cultivars. The NPS combated the disease's local insect vector, the smaller European elm bark beetle (Scolytus multistriatus), by trapping and by spraying with insecticides. As a result, the population of American elms planted on the Mall and its surrounding areas has remained intact for more than 80 years.[42]

In 1997, a European Union elm project was initiated, its aim to coordinate the conservation of all the elm genetic resources of the member states and, among other things, to assess their resistance to Dutch elm disease. Accordingly, over 300 clones were selected and propagated for testing.[54][55][56]

Many elm (Ulmus) trees of various kinds have attained great size or otherwise become particularly noteworthy.

Many artists have admired elms for the ease and grace of their branching and foliage, and have painted them with sensitivity. Elms are a recurring element in the landscapes and studies of, for example, John Constable, Ferdinand Georg Waldmüller, Frederick Childe Hassam, Karel Klinkenberg,[57] and George Inness.

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  John Constable, 'Study of an Elm Tree' [1821]
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  John Constable, 'The Cornfield' [1826] (Ulmus × hollandica[1])
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  Constable, 'Salisbury Cathedral from the Bishop's Garden' [1823 version] (Ulmus × hollandica[1])
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  Jacob George Strutt, Elms at Mongewell, Oxfordshire [1830] (Ulmus minor 'Atinia')
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  Ferdinand Georg Waldmüller, 'Alte Ulmen im Prater' (:Old Elms in Prater) [1831]
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  James Duffield Harding, 'The Great Exhibition of 1851' (Ulmus minor 'Atinia', centre)
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  Arthur Hughes, 'Home from Sea' [1862] (Ulmus minor 'Atinia'[1])
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  Ford Madox Brown, 'Work' [1863] (Ulmus minor 'Atinia'[1])
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  [unknown artist] The American Elm [1879] (Ulmus americana)
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  Johannes Karel Christiaan Klinkenberg, 'Amsterdam' [1890] (Ulmus x hollandica ‘Belgica' )
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  Frederick Childe Hassam, 'Champs Elysées, Paris' [1889] (Ulmus × hollandica, 'orme femelle'[1])
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  Frederick Childe Hassam, 'Washington Arch, Spring' [1893] (Ulmus americana)
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  Frederick Childe Hassam, 'Church at Old Lyme' [1905] (Ulmus americana)
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  Frederick Childe Hassam, 'The East Hampton Elms in May' [1920] (Ulmus americana)
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  George Inness, 'Old Elm at Medfield' (Ulmus americana)
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  Unknown artist, 'The Cam near Trinity College, Cambridge', England (Ulmus atinia)
• 
  Sava Šumanović, Elm [1939]

Achilles and Scamander

Dryad

In Greek mythology the nymph Ptelea (Πτελέα, Elm) was one of the eight Hamadryads, nymphs of the forest and daughters of Oxylos and Hamadryas.[58] In his Hymn to Artemis the poet Callimachus (3rd century BC) tells how, at the age of three, the infant goddess Artemis practised her newly acquired silver bow and arrows, made for her by Hephaestus and the Cyclopes, by shooting first at an elm, then at an oak, before turning her aim on a wild animal:

πρῶτον ἐπὶ πτελέην, τὸ δὲ δεύτερον ἧκας ἐπὶ δρῦν, τὸ τρίτον αὖτ᾽ ἐπὶ θῆρα.[59]

The first reference in literature to elms occurs in the Iliad. When Eetion, father of Andromache, is killed by Achilles during the Trojan War, the Mountain Nymphs plant elms on his tomb ("περί δὲ πτελέας ἐφύτευσαν νύμφαι ὀρεστιάδες, κoῦραι Διὸς αἰγιόχoιo").[60] Also in the Iliad, when the River Scamander, indignant at the sight of so many corpses in his water, overflows and threatens to drown Achilles, the latter grasps a branch of a great elm in an attempt to save himself ("ὁ δὲ πτελέην ἕλε χερσὶν εὐφυέα μεγάλην".[61]

The Nymphs also planted elms on the tomb in the Thracian Chersonese of "great-hearted Protesilaus" ("μεγάθυμου Πρωτεσιλάου"), the first Greek to fall in the Trojan War. These elms grew to be the tallest in the known world; but when their topmost branches saw far off the ruins of Troy, they immediately withered, so great still was the bitterness of the hero buried below, who had been loved by Laodamia and slain by Hector.[62][63][64] The story is the subject of a poem by Antiphilus of Byzantium (1st century AD) in the Palatine Anthology:

Θεσσαλὲ Πρωτεσίλαε, σὲ μὲν πολὺς ᾄσεται αἰών,

Tρoίᾳ ὀφειλoμένoυ πτώματος ἀρξάμενoν•

σᾶμα δὲ τοι πτελέῃσι συνηρεφὲς ἀμφικoμεῦση

Nύμφαι, ἀπεχθoμένης Ἰλίoυ ἀντιπέρας.

Δένδρα δὲ δυσμήνιτα, καὶ ἤν ποτε τεῖχoς ἴδωσι

Tρώϊον, αὐαλέην φυλλοχoεῦντι κόμην.

ὅσσoς ἐν ἡρώεσσι τότ᾽ ἦν χόλoς, oὗ μέρoς ἀκμὴν

ἐχθρὸν ἐν ἀψύχoις σώζεται ἀκρέμoσιν.[65]

[:Thessalian Protesilaos, a long age shall sing your praises,

Of the destined dead at Troy the first;

Your tomb with thick-foliaged elms they covered,

The nymphs, across the water from hated Ilion.

Trees full of anger; and whenever that wall they see,

Of Troy, the leaves in their upper crown wither and fall.

So great in the heroes was the bitterness then, some of which still

Remembers, hostile, in the soulless upper branches.]

Protesilaus had been king of Pteleos (Πτελεός) in Thessaly, which took its name from the abundant elms (πτελέoι) in the region.[66]

Elms occur often in pastoral poetry, where they symbolise the idyllic life, their shade being mentioned as a place of special coolness and peace. In the first Idyll of Theocritus (3rd century BC), for example, the goat-herd invites the shepherd to sit "here beneath the elm" ("δεῦρ' ὑπὸ τὰν πτελέαν") and sing. Beside elms Theocritus places "the sacred water" ("το ἱερὸν ὕδωρ") of the Springs of the Nymphs and the shrines to the nymphs.[67]

The Sibyl and Aeneas

Aside from references literal and metaphorical to the elm and vine theme, the tree occurs in Latin literature in the Elm of Dreams in the Aeneid.[68] When the Sibyl of Cumae leads Aeneas down to the Underworld, one of the sights is the Stygian Elm:

In medio ramos annosaque bracchia pandit

ulmus opaca, ingens, quam sedem somnia vulgo

uana tenere ferunt, foliisque sub omnibus haerent.

[:Spreads in the midst her boughs and agéd arms

an elm, huge, shadowy, where vain dreams, 'tis said,

are wont to roost them, under every leaf close-clinging.]

Virgil refers to a Roman superstition (vulgo) that elms were trees of ill-omen because their fruit seemed to be of no value.[69] It has been noted[70] that two elm-motifs have arisen from classical literature: (1) the 'Paradisal Elm' motif, arising from pastoral idylls and the elm-and-vine theme, and (2) the 'Elm and Death' motif, perhaps arising from Homer's commemorative elms and Virgil's Stygian Elm. Many references to elm in European literature from the Renaissance onwards fit into one or other of these categories.

There are two examples of pteleogenesis (:birth from elms) in world myths. In Germanic and Scandinavian mythology the first woman, Embla, was fashioned from an elm,[71] while in Japanese mythology Kamuy Fuchi, the chief goddess of the Ainu people, "was born from an elm impregnated by the Possessor of the Heavens".[72]

Under the elm, Brighton, 2006

The elm occurs frequently in English literature, one of the best known instances being in Shakespeare's A Midsummer Night's Dream, where Titania, Queen of the Fairies, addresses her beloved Nick Bottom using an elm-simile. Here, as often in the elm-and-vine motif, the elm is a masculine symbol:

Sleep thou, and I will wind thee in my arms.

... the female Ivy so

Enrings the barky fingers of the Elm.

O, how I love thee! how I dote on thee![73]

Another of the most famous kisses in English literature, that of Paul and Helen at the start of Forster's Howards End, is stolen beneath a great wych elm.

The elm tree is also referenced in children's literature. An Elm Tree and Three Sisters by Norma Sommerdorf is a children's book about three young sisters that plant a small elm tree in their backyard.[74]

The cutting of the elm was a diplomatic altercation between the Kings of France and England in 1188, during which an elm tree near Gisors in Normandy was felled. [75]

In politics the elm is associated with revolutions. In England after the Glorious Revolution of 1688, the final victory of parliamentarians over monarchists, and the arrival from Holland, with William III and Mary II, of the 'Dutch Elm' hybrid, planting of this cultivar became a fashion among enthusiasts of the new political order.[76][77]

In the American Revolution 'The Liberty Tree' was an American white elm in Boston, Massachusetts, in front of which, from 1765, the first resistance meetings were held against British attempts to tax the American colonists without democratic representation. When the British, knowing that the tree was a symbol of rebellion, felled it in 1775, the Americans took to widespread 'Liberty Elm' planting, and sewed elm symbols on to their revolutionary flags.[78][79] Elm-planting by American Presidents later became something of a tradition.

In the French Revolution, too, Les arbres de la liberté (:Liberty Trees), often elms, were planted as symbols of revolutionary hopes, the first in Vienne, Isère, in 1790, by a priest inspired by the Boston elm.[78] L'Orme de La Madeleine (:the Elm of La Madeleine), Faycelles, Département de Lot, planted around 1790 and surviving to this day, was a case in point.[80] By contrast, a famous Parisian elm associated with the Ancien Régime, L'Orme de Saint-Gervais in the Place St-Gervais, was felled by the revolutionaries; church authorities planted a new elm in its place in 1846, and an early 20th-century elm stands on the site today.[81] Premier Lionel Jospin, obliged by tradition to plant a tree in the garden of the Hôtel Matignon, the official residence and workplace of Prime Ministers of France, insisted on planting an elm, so-called 'tree of the Left', choosing the new disease-resistant hybrid 'Clone 762' (Ulmus 'Wanoux' = Vada).[82] In the French Republican Calendar, in use from 1792 to 1806, the 12th day of the month Ventôse (= 2 March) was officially named "jour de l'Orme", Day of the Elm.

Liberty Elms were also planted in other countries in Europe to celebrate their revolutions, an example being L'Olmo di Montepaone, L'Albero della Libertà (:the Elm of Montepaone, Liberty Tree) in Montepaone, Calabria, planted in 1799 to commemorate the founding of the democratic Parthenopean Republic, and surviving until it was brought down by a recent storm (it has since been cloned and 'replanted').[83] After the Greek Revolution of 1821–32, a thousand young elms were brought to Athens from Missolonghi, "Sacred City of the Struggle" against the Turks and scene of Lord Byron's death, and planted in 1839–40 in the National Garden.[84][85] In an ironic development, feral elms have spread and invaded the grounds of the abandoned Greek royal summer palace at Tatoi in Attica.

In a chance event linking elms and revolution, on the morning of his execution (30 January 1649), walking to the scaffold at the Palace of Whitehall, King Charles I turned to his guards and pointed out, with evident emotion, an elm near the entrance to Spring Gardens that had been planted by his brother in happier days. The tree was said to be still standing in the 1860s.[86]

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  Planting a Liberty Tree (un arbre de la liberté) during the French Revolution. Jean-Baptiste Lesueur, 1790
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  Balcony with elm symbol, overlooking the 'Crossroads of the Elm', Place Saint-Gervais, Paris[81]
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  President George W. Bush and Laura Bush planting a disease-resistant 'Jefferson' Elm before the White House, 2006
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  Elm suckers spreading before the abandoned summer royal palace in Tatoi, Greece, Μarch 2008

The name of what is now the London neighborhood of Seven Sisters is derived from seven elms which stood there at the time when it was a rural area, planted a circle with a walnut tree at their centre, and traceable on maps back to 1619.[87][88]

A rooted cutting of European White Elm (July)

Elm propagation methods vary according to elm type and location, and the plantsman's needs. Native species may be propagated by seed. In their natural setting native species, such as wych elm and European White Elm in central and northern Europe and field elm in southern Europe, set viable seed in ‘favourable' seasons. Optimal conditions occur after a late warm spring.[1] After pollination, seeds of spring-flowering elms ripen and fall at the start of summer (June); they remain viable for only a few days. They are planted in sandy potting-soil at a depth of one centimetre, and germinate in three weeks. Slow-germinating American Elm will remain dormant until the second season.[89] Seeds from autumn-flowering elms ripen in the Fall and germinate in the spring.[89] Since elms may hybridize within and between species, seed-propagation entails a hybridisation risk. In unfavourable seasons elm seeds are usually sterile. Elms outside their natural range, such as Ulmus procera in England, and elms unable to pollinate because pollen-sources are genetically identical, are sterile and are propagated by vegetative reproduction. Vegetative reproduction is also used to produce genetically identical elms (clones). Methods include the winter transplanting of root-suckers; taking hardwood cuttings from vigorous one-year-old shoots in late winter,[90] taking root-cuttings in early spring; taking softwood cuttings in early summer;[91] grafting; ground and air layering; and micropropagation. A bottom heat of 18 degrees[92] and humid conditions are maintained for hard- and softwood cuttings. The transplanting of root-suckers remains the easiest and commonest propagation-method for European field elm and its hybrids. For 'specimen' urban elms, grafting to wych-elm root-stock may be used to eliminate suckering or to ensure stronger root-growth. The mutant-elm cultivars are usually grafted, the ‘weeping' elms 'Camperdown' and 'Horizontalis' at 2–3 m (6 ft 7 in–9 ft 10 in), the dwarf cultivars 'Nana' and 'Jacqueline Hillier' at ground level. Since the Siberian Elm is drought-tolerant, in dry countries new varieties of elm are often root-grafted on this species.[93]

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  Ripe seeds of field elm
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  Rock elm Ulmus thomasii germinating
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  Seedling of wych elm Ulmus glabra (photograph: Mihailo Grbić)
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  Root-suckers spreading from field elm Ulmus minor
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  Root cuttings of Ulmus 'Dodoens' (photograph: Mihailo Grbić)
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  Rooted hardwood elm-cutting (photograph: Mihailo Grbić)
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  Rooting of softwood elm-cuttings under mist-propagation system (photograph: Mihailo Grbić)
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  Mutant variegated Smooth-leafed Elm graft (photograph: Mihailo Grbić)
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  Air layering of U. pumila (photograph: Mihailo Grbić)
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  In vitro propagation of Ulmus chenmoui by bud meristem (photograph: Mihailo Grbić)
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  Aerial roots, hybrid elm cultivar

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  'Pouch' leaf-galls on a wych elm (aphid Tetraneura ulmi), Germany.
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  'Pouch' leaf-gall on elm leaf (aphid Tetraneura ulmi), Netherlands.
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  'Cockscomb' leaf-galls (aphid Colopha compressa), Poland.
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  'Bladder' leaf-galls on elm leaves (aphid Eriosoma lanuginosum), Italy.
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  'Bladder' leaf-galls on a narrow-leaved elm (aphid Eriosoma lanuginosum), Italy.
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  Aphids in leaf-gall, Poland.
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  'Pimple' leaf-galls on a field elm (mite Eriophyes ulmi), Spain.
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  White-letter Hairstreak Satyrium w-album, on Lutece, Sweden. The larvae feed only on elm.
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  Egg of Satyrium w-album near flower-bud of an elm.
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  Elm-bark beetle Scolytus multistriatus (size: 2–3 mm), a vector for Dutch Elm Disease
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  Scolytus multistriatus 'galleries' under elm-bark.
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  Elm-leaf beetle Xanthogaleruca luteola, which causes serious damage to elm foliage.
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  Xanthogaleruca luteola: caterpillar on elm-leaf, Germany.
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  Elm-leaf damage caused by Xanthogaleruca luteola, Germany.
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  Bacterial infection Erwinia carotovora of elm sap, which causes 'slime flux' ('wetwood') and staining of the trunk (here on a Camperdown Elm).

• Elm Conflict
• List of Elm cultivars, hybrids and hybrid cultivars
• List of Elm species and varieties by scientific name
• List of Lepidoptera that feed on elms
• Fab Tree Hab

• Richens, R. H. (1983). Elm. Cambridge University Press. ISBN 0-521-24916-3. A scientific, historical and cultural study, with a thesis on elm-classification, followed by a systematic survey of elms in England, region by region. Illustrated.
• Heybroek, H. M., Goudzwaard, L, Kaljee, H. (2009). Iep of olm, karakterboom van de Lage Landen (:Elm, a tree with character of the Low Countries). KNNV, Uitgeverij. ISBN 9789050112819. A history of elm planting in the Netherlands, concluding with a 40 – page illustrated review of all the DED – resistant cultivars in commerce in 2009.

• Clouston, B.; Stansfield, K., eds. (1979). After the Elm. London: Heinemann. ISBN 0-434-13900-9. A general introduction, with a history of Dutch elm disease and proposals for re-landscaping in the aftermath of the pandemic. Illustrated.
• Coleman, M., ed. (2009). Wych Elm. Edinburgh. ISBN 978-1-906129-21-7. A study of the species, with particular reference to the wych elm in Scotland and its use by craftsmen.
• Dunn, Christopher P. (2000). The Elms: Breeding, Conservation, and Disease-Management. New York: Boston, Mass. Kluwer academic. ISBN 0-7923-7724-9.
• Wilkinson, G. (1978). Epitaph for the Elm. London: Hutchinson. ISBN 0-09-921280-3. A photographic and pictorial celebration and general introduction.

Wikimedia Commons has media related to Ulmus.

• "Elm trials". Northern Arizona University.
• Tree Family Ulmaceae Diagnostic photos of Elm species at the Morton Arboretum
• "Late 19th and early 20th-century photos of Elm species in Elwes & Henry's Trees of Great Britain & Ireland, v. 7" (PDF). 1913.
• "Elm Photo Gallery".
• Eichhorn, Markus (May 2010). "Elm – The Tree of Death". Test Tube. Brady Haran for the University of Nottingham.
• Texts on Wikisource:
  • Ripley, George; Dana, Charles A., eds. (1879). "Elm". The American Cyclopædia.
  • "Elm". New International Encyclopedia. 1905.
  • "Elm". Encyclopædia Britannica (11th ed.). 1911.
  • "Elm". Encyclopedia Americana. 1920.
  • "Elm". Collier's New Encyclopedia. 1921.