Wych Elm and Dutch Elm Disease: Scotland's Lost Trees

Each major claim carries one of three labels. established means supported by primary records, official bodies or several independent reliable sources. shared means the core fact is sound but sources disagree on details, dates or interpretation. traditional means widely repeated but not traceable to a primary or independent source.

Estimates of the number of elms killed vary. The cause of the Neolithic elm decline is debated.

The wych elm

established The wych elm is a large, broad-crowned tree, native to Scotland and found mainly in woodlands, glens and along rivers. Its leaves are large and rough, with a lop-sided base. Unlike English elm, it reproduces readily from seed. Its timber was used for coffins, furniture and boats, and its flexible wood was used for bows.

The disease

established Dutch elm disease is named after the Dutch scientists who studied it in the 1920s. It is caused by fungi carried by elm bark beetles, which breed under the bark of dying elms and fly to healthy trees. The fungus blocks the water-conducting vessels, causing leaves to wilt and the tree to die. In the late 1960s a much more aggressive strain, Ophiostoma novo-ulmi, arrived in Britain, probably on imported elm logs.

Devastation

established The new strain killed tens of millions of elms in Britain within a few decades, transforming the landscape. It reached Scotland in the 1970s and has continued to spread north, killing wych elms in woods and towns.

Edinburgh's elms

established Edinburgh retains one of the largest populations of elms in Britain, thanks partly to a programme of surveying, prompt felling and removal of infected trees to reduce beetle breeding. Despite this, the city continues to lose trees each year.

The Neolithic elm decline

shared Pollen records show a sudden decline in elm across north-west Europe around 4000 BC. Some scientists think an outbreak of elm disease played a part, alongside clearance and leaf-cutting by early farmers and climate change. The question remains open.

The elms in Flora Britannica (1996)

established A species apart. Richard Mabey, in Flora Britannica (1996), describes the wych elm as "really a species apart" from the other British elms. It is the only one that regularly produces seedlings in Britain, it does not sucker, and it rarely grows naturally outside woods. Pollen evidence shows it was already present before Neolithic farmers arrived. Most other elms spread by root suckers into clones, which is why lowland English elms vary so much from village to village. Mabey also points out a confusing name: the so-called "Dutch elm" of the timber trade, U. × hollandica, is a hybrid between wych elm and smooth-leaved elm, and has nothing to do with the disease's name.

established An old disease. Mabey stresses that the disease is not new and that elms have always crept back. He lists an epidemic in southern England between 1819 and 1864 and another in Oxford in the 1780s, and suggests the dead elms common in Italian paintings of 1450 to 1530 were almost certainly victims too. He quotes Oliver Rackham's question of why it was possible in the eighteenth century to insure elms against death. Mabey names the fungus Ceratocystis ulmi, the name then in use; the aggressive strain is now classed as Ophiostoma novo-ulmi.

established Waves, not a single blow. Mabey describes the 1980s recovery, when shoots and suckers from apparently dead elm stumps grew up to 30 feet and began to flower again, only to be struck once more in the early 1990s. He explains this as a see-saw between the fungus, the beetles and viruses that infect the fungus and weaken it. Almost all the suckering types can survive as bushes, he notes; the wych elm, which does not sucker, lacks that particular fallback and depends more on seed for recovery.

shared The date of the prehistoric decline. Mabey dates the Elm Decline to about 3000 BC, an older uncalibrated radiocarbon date. Calibrated dates now put it around 4000 BC, the figure used in this article. Both refer to the same event.

established Uses. Mabey records that elm timber was used wherever durability in wet conditions was needed: water pipes, floorboards and coffins. Its irregular grain, especially in burrs, was valued for furniture. He also quotes the old saying "Elm hateth Man and waiteth", from the tree's habit of dropping great branches without warning. His records of elm customs come from England; he gives nothing specific to Scotland.

• The wych elm is the only British elm that regularly grows from seed; the others spread mainly by root suckers.
• The "Dutch elm" of the timber trade is a hybrid of wych elm and smooth-leaved elm; it is not named after the disease.
• Elm disease is old: there were outbreaks in Oxford in the 1780s and southern England between 1819 and 1864.
• Elm wood lasts well when wet, so it was used for water pipes and coffins.
• The wych elm is Scotland's native elm.
• Dutch elm disease is spread by bark beetles.
• The aggressive strain arrived in Britain in the late 1960s.
• Edinburgh has one of Britain's largest remaining elm populations.
• Elm declined sharply in prehistory too.

• Do not give a precise number of elms killed.
• Do not state the cause of the Neolithic decline as settled.
• Do not treat Dutch elm disease as a disease first seen in the twentieth century; earlier epidemics are recorded.
• Do not confuse the "Dutch elm" hybrid with the disease.