Historically, elm was one of the six major components of British woodland, and was also used widely in landscaping, notably by Capability Brown. In addition to the White-letter Hairstreak butterfly, elm hosts more than 80 other species of invertebrate in the UK, including several rare moths. Elm timber is prized for its strength and durability and was once a mainstay of British furniture.

Dutch elm disease (DED) is caused by a pathogenic microfungus invading the water-conducting vessels of elms. The tree reacts by blocking the vessels in an attempt to isolate the disease, but this causes wilting, defoliation, and usually death. The first, relatively mild, pandemic was first reported in the UK in 1910. Since the outbreak of the current, three times more lethal, epidemic of DED in the early 1960s, the disease has killed nearly all the mature elms in Britain; an estimated toll of 60-100 million trees.

The first DED fungus, Ophiostoma ulmi, is believed to have originated in Asia but was accidentally introduced to Europe and North America; it was identified by Dutch scientists in the 1920s

In Britain, the disease is spread by two species of elm bark beetle, which breed in the bark of infected or recently killed elms. When the new beetle broods disperse in summer, they carry fungal spores on their bodies which then infect healthy trees as the beetles feed on the thin-barked twigs in the tree canopy.

Historically significant elms can be injected with a fungicide which can cure newly infected trees. However, this a specialized and expensive operation which must be repeated every two or three years. Consequently, it is not a practical solution for protecting elms in the wider countryside. The spread of DED can be controlled by felling and burning diseased trees (: ‘sanitization’) immediately symptoms are evident, before the beetles can breed in them, but this too is labour intensive and costly.

Elms with a genetic resistance to DED have evolved in Asia, where the disease has existed for thousands, possibly millions, of years. Breeding programmes in Europe have hybridized several of these species with wych and field elm to create resistant trees with a passing resemblance to our native species. In the United States, crossing Siberian elm with Japanese elm has produced several very good cultivars now propagated in Europe, primarily intended for street planting rather than repopulating the wider landscape. More recently, there has been a concerted effort in Europe to identify field elms (U. minor) with a high resistance to DED, with several notable successes in Spain, although these have yet to appear in commerce.