Moreover, during the 19th and early 20th centuries, many species and cultivars were also planted as ornamental street, garden, and park trees in Europe, North America, and parts of the Southern Hemisphere, notably Australasia.

Elm leaves are alternate, with simple, single- or, most commonly, doubly serrate margins, usually asymmetric at the base and acuminate at the apex.

Owing to its geographical isolation and effective quarantine enforcement, Australia has so far remained unaffected by DED, as have the provinces of Alberta and British Columbia in western Canada.

Woodland trees in North America are not quite as susceptible to the disease because they usually lack the root grafting of the urban elms and are somewhat more isolated from each other.

In France, inoculation with the fungus of over 300 clones of the European species failed to find a single variety that possessed of any significant resistance.

[18] No sign indicates the current pandemic is waning, and no evidence has been found of a susceptibility of the fungus to a disease of its own caused by d-factors: naturally occurring virus-like agents that severely debilitated the original O. ulmi and reduced its sporulation.

Their quick growth and variety of foliage and forms,[26] their tolerance of air-pollution, and the comparatively rapid decomposition of their leaf litter in the fall were further advantages.

In northern Europe, elms were among the few trees tolerant of saline deposits from sea spray, which can cause "salt-burning" and die-back.

Since around 1990, the elm has enjoyed a renaissance through the successful development in North America and Europe of cultivars highly resistant to DED.

[3] 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.

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.

Research has followed two paths: In North America, careful selection has produced a number of trees resistant not only to DED, but also to the droughts and cold winters that occur on the continent.

Research in Spain has suggested that it may be the presence of a triterpene, alnulin, which makes the tree bark unattractive to the beetle species that spread the disease.

[38] More recently, field elms Ulmus minor highly resistant to DED have been discovered in Spain, and form the basis of a major breeding programme.

Dutch hybridizations invariably included the Himalayan elm (Ulmus wallichiana) as a source of antifungal genes and have proven more tolerant of wet ground; they should also ultimately reach a greater size.

However, the susceptibility of the cultivar 'Lobel', used as a control in Italian trials, to elm yellows has now (2014) raised a question mark over all the Dutch clones.

[41] Elms take many decades to grow to maturity, and as the introduction of these disease-resistant cultivars is relatively recent, their long-term performance and ultimate size and form cannot be predicted with certainty.

[51] 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.

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.

[53] Elm wood is valued for its interlocking grain, and consequent resistance to splitting, with significant uses in wagon-wheel hubs, chair seats, and coffins.

[56] Elm wood is also resistant to decay when permanently wet, and hollowed trunks were widely used as water pipes during the medieval period in Europe.

Lopped at 3 m, the elms' quick growth, twiggy lateral branches, light shade, and root suckering made them ideal trees for this purpose.

[59] The mucilaginous inner bark of the slippery elm (Ulmus rubra) has long been used as a demulcent, and is still produced commercially for this purpose in the US with approval for sale as a nutritional supplement by the Food and Drug Administration.

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").

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.

[77] 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 (third century BC), for example, the goatherd invites the shepherd to sit "here beneath the elm" ("δεῦρ' ὑπὸ τὰν πτελέαν") and sing.

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.

[97] The name of what is now the London neighbourhood 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.