Picture, looking out of a cottage window to where stands a dead tree. It is not big, perhaps 15ft tall; a song thrush has used it as a song post for the past year, singing with a silver throat from dawn till dusk, from mid-winter through into summer. The tree has been dead for two years now and rather oddly, it has in a sense been dead before. It is, an English Elm, which can often rejuvenate via suckers from its route system. Judging by old photographs, our tree was once as tall and majestic as any tree on the landscape before it succumbed to Dutch Elm Disease (DED), during the 1970’s.
Elm, it’s a short, distinctive word, resonating like a cherished wooden bowl. In many parts of the country, as elms succumbed to DED they were either cut down or, were left standing in the wake of the disease, their gaunt skeletons littering the landscape, their bark detaching after a few years. Elm (Ulmus) is in the super-family of plants which includes stinging nettle, hop and cannabis. Elm timber will not cleave or split making it ideal specialised uses such as wheel hubs; elm was also used for weather boarding on traditional buildings. It is also extremely resilient when submerged beneath water and was used in connection with water-mills, lock gates and also in shipbuilding.
Most elm leaves have toothed edges, these two edges meeting at the stalk unevenly. Often during late autumn, just for a few days, the hedgerows around the Downs used to be ablaze with a flare of the most vivid lemon-yellow you will ever see in a leaf! It is something that you will only find in the few country lanes where the elms remain, increasingly only as hedges and, along the thoroughfares and streets of Brighton and Eastbourne. As you round a bend in the road one is confronted by this burst of dazzling colour, as though you have entered a wedding scene, scattered with oversized, yellow confetti! This leaf-fall does not last very long and does not happen every year, it being dependent on the frequency of autumn gales and often coinciding with the first frosts.
Dutch Elm Disease (DED) has a long history. It is ‘Dutch’ only insofar that it was first identified by scientists in the Netherlands. The disease has ravaged the elm family from time to time over the millennia. We know that within a century or two of 4,000BC half of Europe’s elm disappeared. At the point of that decline, elms covered an eighth of the British Isles. In other words, the tree was phenomenally successful and well-adapted, though it seems likely the disease decimated the elm even then, as evidence of one of the carrier beetles dating from that time was recovered.
Twentieth century DED, Ophiostoma ulmi, first appeared in north-west Europe in 1910; the first British case being found in 1927. The disease initially killed between 10-40 per cent of the British elm population but this gradually lessoning over the years. However, the second epidemic of DED which arrived in the UK during the late 1960’s on infected elm logs from North America, had by 1979 killed 25 million mature elms. This new disease – for it is caused by a new species of fungus named Ophiostoma novo-ulmi, probably came about from a mutation occurring in Asia (Himalayas?) and is one of the worldís most virulent tree diseases. DED causes the elm to try and protect itself by clogging-up its own transport system (xylem vessels); these should convey water from the roots of the tree up to the leaves, the disease causing the characteristic brown wilting, first of very outer branches, then the whole crown, before blighting the entire tree. With hedgerow elms, it then enters down into the inter-connecting root system and spreads from tree to tree.
The fungus is initially carried externally on two species of bark-eating beetle that are specific to elm species (but mainly Scolytus scolytus in Sussex), flying from tree to tree infecting the xylem while feeding with fungus and choosing to lay their eggs under the bark of recently dead or diseased trees. The young larvae eat creating radiating tunnels before they pupate and over-winter; the tunnels that they bore are also infected with the fungus. When the young adults emerge in spring and fly away, they in turn carry spores of the fungus to yet more elms. It seems they only fly when the temperature is above 20C, which explains why the disease spreads so fast in the notably hot springs and summers of recent years. So unless our elms develop a natural defence or, the fungus weakens, climate change may well finish what nature (with help from Man’s modern global transport web) started?
English Elm, Ulmus procera, is the only tree in the UK that clones itself, so that a hedgerow’s plants are all identical in every detail and could attain heights of up to 150 feet (45metre) tall. The upper surfaces of its smallish leaves are rough to the touch, with hairs on the underside. The common name English is possibly fraudulent as recent DNA work has established that the species appears to have arisen in the area around Rome about two thousand years or more ago, as a support for growing vines on. It was then introduced into Iberia and finally into the British Isles. Generally, as long as trees are felled before they die from disease or old age, the plant via its suckers, will live almost indefinitely and uniquely, in exactly the same cellular form, despite repeated reincarnations. Most current hedgerow elms have established from root systems of dead trees. It also means that what surviving English elms we have are living links with our distant past, because they will be clonal material from roots that were planted possibly some 2,000 years ago. English elm does not produce fertile seeds. Now of course, large mature English elms are as rare as honest politicians, with only a relative handful left, although I can clearly remember the lanes and tracks of decades ago lined with elms up to 100ft (30metre) tall. In summertime, they elegantly held a spreading crown of foliage, the classic ‘anvil-headed’ or thunder-cloud elm silhouette. In winter, they would stand gaunt against a rainy sky, with faces to be found in the branches. The best concentrations of large specimens now, are at Pavilion Parade and at Preston Park, both within Brighton. The Preston Twins, are possibly the two oldest English elms in the world. Both trees are aged over 400 years and exceed 6 metres in girth. They have been regularly pollarded over many years and both trunks are hollow. The smaller, nearer the A23 London Road, can be entered from the east side; two people can stand comfortably inside it.
Wych Elm, Ulmus glabra, its larger, leaves often obscuring the short leaf stalks; they can become large trees up to 120 feet (37metres) tall. It is more fan-shaped than the English elm, with the lower branches typically swooping down and then up again. It is atypical in that it does not sucker, but spreads by seed. Nevertheless, it was by far the most common elm in the north and also common in parts of East Anglia. DED has spread rather more slowly in Scotland than in the south because of the preponderance of the Wych elm and also because of a smaller, less-efficient beetle vector and possibly less days of warm flight weather. The great timber advantage that it has over English elm is that it will split, thus making it much more amenable to carpentry.
The Wheatley Elm, Ulmus minor var. sarniensis, (sometimes referred to as ‘Guernsey Elm), is one of the smooth-leaved elms, (so called because the English elm’s leaves are rough to the touch) and is the classic, spire-shaped street elm of Brighton and our coastal towns. The Guernsey Elm was reported in 1815 to be “confined to Guernsey” but was in English nurserymen’s catalogues by the 1830’s. With its light, upcurving branches it never became a danger, unlike English elm, which sometimes sheds heavy lateral boughs. This fact and its compact form, made it ideal for street planting. Among the largest surviving specimens in the UK are two in Warriston Cemetery, Edinburgh (2011), with girths of 3 metres and the one in Preston Park, which is 34 metres tall with a trunk 115cm diameter at breast height in 2006, part of a line of trees averaging 30 metres in height planted in about 1880. The tallest on record in the UK stands on Paradise Drive, Eastbourne and had a height of 36 metres in 2007. There is also still a fine specimen on the outskirts of Lewes close to the A26 road.
Smooth-leaved Elms group, includes a number of varieties and cultivars; their young branches are sometimes conspicuously furnished with wing-like outgrowths of corky bark. Much of the seed produced by this grouping is not fertile.
East Sussex Dutch Elm Control Area. In East Sussex, a coastal area and parts of the neighbouring Adur DC, Brighton & Hove (which also contains the National Elm Collection) and Eastbourne local authority areas, combined during the early 1970’s to create a Dutch Elm Control Area with its main method of defence being sanitation felling that is, any infected tree which showed symptoms of the disease being felled or, partially de-limbed. The Area had the advantage of having the sea to the south, the largely treeless Downs to the north and a prevailing south-westerly wind. It contained the largest population of English elm in the world.
In the East Sussex County Council zone (the campaign here being operated by the Sussex Downs Conservation Board between 1997 and 2007), the ESCC provided sufficient funding to meet the cost of felling elms on private property, gaining the support and co-operation of a vast majority of landowners. This policy enabled prompt action being carried out by dedicated contractors, so vital to the success of the scheme. By the close of 1996 less than 20% of the Control Area’s elms had been identified as being infected, whereas in the remainder of Sussex and neighbouring counties, 80% of the elm population had been decimated. In the early 2000’s, infection rates on the then total elm population of some 53,000 trees, were only in the region of 2-3%. However since 2008, due to mis-management, then changes in funding policy and administration of felling work, the ESCC-controlled zone of the Control Area is now at the time of writing, riddled with dead and dying elm trees with the tallest specimens having been hit particularly hard. This alarming scenario now threatens the good work still being carried out in the Brighton and Eastbourne areas by the possibility of larger numbers of elm bark beetles being blown into those areas during flight periods.
Update July 2018 – There are to my knowledge, now only two large elms remaining in the rural part of the former ESCC-controlled zone: a rare variety of smooth-leaved elm by the Black Barn at Lullington and a Wheatley elm at by the A26 at Malling in Lewes.
Also now, there is yet another threat to our elm tree population; pest which leaves a zigzag signature trail of destruction on elm leaves has arrived in the UK, experts at the Royal Botanic Garden in Edinburgh have announced. The tell-tale zigzag feeding trail left behind by the sawfly larvae has been found on leaves collected during the autumn of 2017 in Surrey – part of a plant survey being carried out. The zigzag elm sawfly, originally found in Japan, feeds only on elm leaves and has been progressing steadily through Europe. The discovery has raised concerns it could pose another blow to the UK’s elms, which have already been devastated by Dutch elm disease, and threaten wildlife that rely on the trees. While the zigzag elm sawfly rarely kills trees, large populations can completely defoliate elms, which could be disastrous for the white-letter hairstreak whose populations are dependent on elm.
The idea for this article started with reading a short article in The Observer of Sunday, November 6 2005 by Monty Don about his book, ‘My Roots: A Decade in the Garden,’ published by Hodder & Stoughton. I have used part of it and added much additional research, observations and have also put a Sussex twist into it. Thank you Monty, for the seed idea! Thanks are also due to local elm expert Mary Parker, on a number of technical points.
‘After The Elm;’ Brian Clouston & Kelly Stansfield. Heinemann. 1979.
‘A Reappraisal of British Elms Based on DNA Evidence;’ Ken Adams. 2006. http://www.s231645534.websitehome.co.uk/mapmate__recording.htm
Building Research Establishment Digest 194. October 1976.
‘Dutch Elm Disease Control ñ A Report by ESCC.’ ESCC. March 1977.
‘Elm Trees and Associated Places of Interest’ Leaflet by Mary Parker. Sussex Downs Conservation Board. 1999.
‘New Horizons in Dutch Elm Disease Control;’ Professor Clive Brasier. Report on Forest Research, Forestry Commission. 1996.
Rob Greenland. See http://www.brightonelmtrees.com/about-me.html For more details on Brighton’s elms.