There are between 30 and 40 species of elms.
Eight of these are native to North America
with the remainder coming from parts of
Europe and
Asia.
The
key challenge for many members of this genus
when used in the landscape in the
United
States is
Dutch elm disease (DED).
This fungal disease was introduced over half
a century ago and has devastated many (but
not all) of the American elms once used
extensively as street and landscape trees.
Different species have differing levels of
susceptibility or resistance to DED.
