Sandy’s Garden ... The Great Elm Tree Mystery

Sandy Simpson
Sandy Simpson

Ophiostoma ulmi – and a gold star goes to any reader familiar with this name.

It is a fungus which attacks elm trees. Although scientists are still unsure about the origins of Ophiostoma ulmi, Japan is becoming the favourite country whence this dreaded fungus came: but to most people Ophiostoma ulmi is known as Dutch elm disease, which is one of the most serious tree diseases in the entire world and has killed over 60 million British elms … yes, 60 million elm trees in the United Kingdom alone … in two epidemics; and it continues to spread to this day.

The first epidemic of Dutch elm disease occurred in the 1920s, when the fungus migrated from its original home … wherever that eventually turns out to be … and spread across Europe, North America and Asia. The fungus is carried by a charming little insect called the elm bark beetle which has definite preferences for certain species of elm as breeding grounds, burrowing into the bark of the trees. This preference for specific types of elm tree helped to end the first epidemic of Dutch elm disease … so called because the first recorded outbreak in Europe was identified by the Dutch phytopathologists Bea Schwarz and Christine Buisman … when, after having infected all the preferred species the beetles could find, they had to turn to disease-resistant species of the tree. Ophiostoma ulmi was also, fortunately, itself to vulnerable to viral infections. Cheers all round!

Sadly, the celebrations were premature. In the early 1970s, a very aggressive variant of Ophiostoma ulmi … called Ophiostoma novo-ulmi … reached the United Kingdom from the United States. This form of the fungus is resistant to viruses and affects almost every know species of elm tree. The second deadly epidemic of Dutch elm disease began; and this epidemic is still ongoing worldwide. And when I write that this second epidemic is “deadly”, that is exactly what I mean. The entire remaining elm tree population of Britain is in danger. But recently two thriving, mature specimens of the always rare and thought-to-be-extinct, royal, 100ft-tall Wentworth elm have been ‘found’ … not, that’s not the right word, for they have been in full public view for more than a century … have been ‘recognised’ … that’s the word … in, appropriately, Her Majesty The Queen’s garden at the Palace of Holyroodhouse, a stone’s throw away from Edinburgh city centre. There they are, standing tall and proud right in the heart of our capital city, survivors of an epidemic which was thought to have killed off every single Wentworth elm - Ulmus ‘Wentworthii Pendula to the arboriculturist.

Cue a quotation from the website of the Royal Botanic Garden Edinburgh (RBGE). ‘“Such a discovery when the trees in question are just shy of 100 feet tall and in plain sight does sound rather odd,” conceded Dr Max Coleman of the RBGE, who identified the specimens after they were noted as being unusual during a tree survey.

“It is very likely the only reason these rare elms have survived is because Edinburgh City Council has been surveying and removing diseased elms since the 1980s. Without that work many more of the thousands of elms in Edinburgh would have been lost. The success of this programme may be partly demonstrated in the way two rare trees have been preserved.”’

How the trees came to be in the Queen’s garden is a mystery. The best guess is that they arrived there from Germany, via the RBGE, in 1902. But the possibility of these … the last surviving Wentworth elms in Britain … being propagated to produce a new generation of their species, means that these majestic trees may be around for future generations to admire.