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The re-emergence of
an old tree killer
By Joe Boggs and Francesca Peduto Hand, PhD
T he rise and fall of American elms
(Ulmus americana) in urban
forests is well-known to arborists.
The story is often used as a
cautionary tale illustrating the elevated
risk posed by plant monocultures to
support devastating pest and disease
outbreaks; in this case, the over-use of
a single tree species in urban plantings.
Conversely, the American elm story is
also used to demonstrate the value of
6 May 2014
Dense, dark green foliage coupled with fast
growth and a stately vase-shaped silhouette
were prized characteristics that inspired the
journey of this North American native from
forests to city streets. The rise of American
elms to become ‘Canada’s street tree’ was
further enhanced by the ability of this species
to cope with a wide array of human-induced
urban abuses. The pinnacle of American elm’s
arching trajectory as an urban tree occurred
when Dutch Elm Disease (DED) was
discovered in North America.
All images courtesy Joe Boggs