Green Horizons Newsletter - AgEBB

AgEBB-MU CAFNR Extension

Green Horizons

Volume 24, Number 1
Winter 2020

Urban Forestry

Elms in America

By Meridith Perkins & Cory Knoblauch | Forest ReLeaf of Missouri

Bark of elm tree infected with DED, Image from:

It has been 90 years since the Dutch elm disease (DED) first arrived in the United States. At that time native American elm trees (Ulmus americana) grew in great numbers across the forested landscape as well as the urban core. The American elm proved tolerant to the challenges of city living and became the go-to tree for park strip plantings along streets. The large, vase shaped elm canopy created green corridors and grew to define neighborhoods everywhere. However, when the United States began importing wood after World War I, the DED fungus (Ceratocystis ulmi) and the European elm bark beetle (Scolytus multistriatus) vector came along for the ride. Within a few decades hundreds of thousands of American elm trees were dying across the USA. There was and is still no effective treatment for trees once they are infected with DED. Few stately American elms remain in Missouri and many of these are treated annually with a preventative fungicide to keep the disease at bay.

After all this, people are not ready to give up on elms! Researchers continue working to isolate DED resistant American elm cultivars and develop elm hybrids that mimic those iconic American elm traits. If you are looking for an elm tree for your home landscape, consider:

Left: American Elm, Right: White Ash Leaves Source:

White Ash Trees,
Image from:

Many elms resistant to DED still suffer from black leaf spot, phytophthora root rot, Japanese beetle, bark beetle, and weak wood structure. For this reason, over the past 50 years a favorite elm tree replacement has been ash. Streets previously lined with American elm were planted with monocultures of green ash (Fraxinus pennsylvanica) or white ash (Fraxinus americana). Now, we are losing this critical tree canopy to the devastating impact of the emerald ash borer!

What we have learned from decades of tree planting investments is that species diversity is the key to a resilient urban forest canopy. Neighborhoods should have a combination of trees from different species, genus, and families. Some underrepresented native trees that may be appropriate for elm tree replacement include: hackberry, river birch, shumard oak, black gum, and bald cypress. Forest ReLeaf of Missouri has these tree species available for spring planting projects through our free tree giveaway program or private sales. Apply in February at

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