The latest Biological Flora of the British Isles account is Ulmus glabra, written by Peter Thomas, Duncan Stone, and Nicole La Porta. Peter Thomas tells us more about Ulmus glabra in the blog post below. Find this account, and the rest of the series, online in the new BFBI database. 

A recent visit to Aberdeen was one of life’s bittersweet moments as we went to the thanksgiving service for Prof Charles Gimingham. There were many sweet, shared memories of a great man but tinged with sadness at his passing away in June.

The very next day saw yet another bittersweet moment as we walked through Aberdeen city reliving old memories. It was a real joy to come across some magnificent, mature specimens of wych elm (Ulmus glabra) growing in the parks and avenues. But the joy was tinged with acute sadness as these lovely trees will almost certainly be gone within my lifetime.

The problem is Dutch elm disease. I can remember the death of huge numbers of elms in the 1970s in my native Kent. The cause was the introduced fungus (Ophiostoma novo-ulmi), virulent to all elm species eventually killing some 28 million elms in the 1970s epidemic.

The wych elm is in a slightly better position than our other elms in that it can regrow from root suckers, and also most importantly, from seed. But new trees grow up till they are about 5-9 meters tall and then again become infected by the disease, creating a 15-25 year cycle of growth and above-ground death. This means that the wych elm will never again be seen as a towering magnificent tree except as the odd, relict individual, mainly in the west of Britain. And currently in Scotland.

Dutch elm disease has been slow to spread in Scotland, mainly because the fungus is transported between trees by beetles, particularly the large elm bark beetle, Scolytus scolytus. Wych elm and the European white elm (U. laevis) are less attractive to the beetle than field elm (U. minor) and Siberian elm (U. pumila) but this does not save them. In the past, cold temperatures have limited the spread of the beetle. But with global warming, the beetle is moving north, taking Dutch elm disease with it. Today it is rampant around Loch Ness, with Glen Urquhart freckled with dead elms, and the disease wave front will have moved further north and west during this hot summer.

So if you like old elms, now is the time to visit northern Scotland and take your fill. Many of the trees won’t be completely killed once the disease arrives, but the sight of the huge old trees will become a thing of the past. And if you want to find out more about wych elm…

Peter Thomas, Keele University, UK

Read the full paper online: Biological Flora of the British Isles: Ulmus glabra and the rest of the series in the new database.