Elm trees: An American Comeback Story

There’s no tree quite like an Elm. With high-arching, grand canopies, this iconic shade tree once was a mainstay lining American streets—including Portland’s own park blocks and neighborhoods like Ladd’s Addition and Eastmoreland—through the 20th century. As urban trees, they were as hearty as it gets.

Then came Dutch elm disease. As soon as it arrived to the states in the 1930s, mature American elms started to disappear by the thousands—then the millions. As many as 9 out of 10 American elms have been lost.

Portland has gone to great lengths to save its elms. The city and neighborhood groups closely monitor each of the 3,500 or so susceptible elms. About 20 or 30 trees test positive for Dutch Elm Disease each year and and must be removed, says Emily Wilson, the Dutch Elm Disease Monitor for Portland Parks and Recreation’s Urban Forestry division.

“At this point, we’re trying to control the spread of the disease and preserve the largest mature elms we have left,” she says.

Portland has the highest concentration of large elms in the downtown park blocks, Ladd’s Addition and Eastmoreland. Each summer hundreds of elms are treated with fungicide in these locations to lengthen the lives of these grand old giants.

Dutch Elm Disease is a fungus that invades a tree’s vascular tissue, blocking water uptake. It’s spread by beetles, which wreak their own havoc on the resulting decay. Affected trees can die within weeks or months.

When Wilson examines an elm tree, she looks for what’s called flagging—a sudden drooping and curling of leaves. “Those leaves are brown and curled because they’re not getting any water,” she says.

If there’s flagging, Wilson peels back the bark on a ½-inch diameter twig to look for dark streaking—the presence of the fungus. If there’s streaking, the sample goes to the plant pathology lab at Oregon State University to confirm Dutch Elm Disease. A positive test means the tree must swiftly removed so it doesn’t infect other trees or cause any damage or harm.

If you think you have an elm that may be affected, you can contact Wilson at [email protected] with the address of the tree and the reason for the concern. “I’m always happy to come out and take a look,” she says.

Elms aren’t going away. If you’re set on planting a young elm tree, you can choose one of a number of hybrid cultivars that are tolerant to Dutch Elm Disease and beetle attacks. Friends of Trees offers the Patriot Elm to residents with large planting strips and the right conditions. Patriot elms grow to be 50 feet tall, have a lovely upsweeping crown and nice yellow fall color.

Patriot Elms and other hybrid cultivars resulted from crossing American elms with Asian varieties, which are disease and beetle tolerant. They’re pretty cool, though they don’t quite grow as large as the native species.

As for the grand old American elm? It may too, soon, be making a comeback. Some of the surviving older elms have been tested and, amazingly, are disease resistant. To test which ones are best, a national elm trial is underway in 18 locations across the U.S. It includes more than 1,000 trees contributed by J. Frank Schmidt & Son Co., one of the nation’s premier tree growers and a longtime supporter of Friends of Trees.

And if you see an elm in your neighborhood or a nearby park, appreciate it for the survivor that it is.