In the fall of 1918, with the dust of the First World War still settling, reports of a mysterious “elm death” spread across northern Europe. As anxieties grew and speculation swirled, there was need for serious science to be done.

By 1921, Director Johanna Westerdijk of the Willie Commelin Scholten Lab in Baarn, Netherlands oversaw a total of 56 researchers devoted to the elm question, almost half of them women. Barendina Spierenbeurg first reported the excessive decline of European elms. Marie Beatrice Schwarz linked the wilt to a new fungus species, which she named Graphium ulmi (now Ophiostoma ulmi). By the time the elm disease hit Britain in 1926, it was widely known as Dutch elm disease.

In 1927, Dr. Christine Buisman identified an alternate stage of the fungus life cycle, shedding light on how it reproduces. As a fellow at Harvard’s Radcliffe College in Cambridge, Dr. Buisman used the Arnold Arboretum’s elm collection to study dieback diseases. Just before her departure from the arboretum in 1930, Buisman identified the first case of Dutch elm disease in the U.S., on a twig sample sent from Ohio.

The discoveries of these Dutch scientists spurred efforts aimed at restoring the elm to the streets of Europe. In 1935, the lab found a resistant selection of Ulmus × hollandica, known as clone 24. Following Buisman’s sudden death in early 1936, U. × hollandica ‘Christine Buisman’ was planted widely as a street tree throughout the Netherlands. The Arnold received this clone in 1946, the first year that it was distributed to the United States. Individuals 135-54*B and 273-46*A are alive today, just a few hundred feet from where this article was written.

Although tolerant of Dutch elm disease, the clone would prove susceptible to other cankering fungi and suffered widespread storm damage. This influenced elm improvement programs to select for cold hardiness, flood tolerance, and stronger branch unions. A newer American elm, ‘Jefferson’, introduced in 2004 by the U.S. National Arboretum and National Park Service, was found to have a unique triploid genome. Suggesting that resistant genotypes exist in the wild, the mutation emphasizes the importance of wild genes for the next century of elm improvement.

Chris Copeland is the assistant manager of plant production at the Arnold Arboretum.

From “free” to “friend”…

Established in 1911 as the Bulletin of Popular Information, Arnoldia has long been a definitive forum for conversations about temperate woody plants and their landscapes. In 2022, we rolled out a new vision for the magazine as a vigorous forum for tales of plant exploration, behind-the-scenes glimpses of botanical research, and deep dives into the history of gardens, landscapes, and science. The new Arnoldia includes poetry, visual art, and literary essays, following the human imagination wherever it entangles with trees.

It takes resources to gather and nurture these new voices, and we depend on the support of our member-subscribers to make it possible. But membership means more: by becoming a member of the Arnold Arboretum, you help to keep our collection vibrant and our research and educational mission active. Through the pages of Arnoldia, you can take part in the life of this free-to-all landscape whether you live next door or an ocean away.

For more tree-entangled art, science, and writing, subscribe to Arnoldia by becoming a member of the Arnold Arboretum.