New York Natural Heritage Program
Cork Elm
Ulmus thomasii Sarg.
Ulmus thomasii (note new growth in foreground, older corky twigs in back. Julie A. Lundgren
Family: Elm Family (Ulmaceae)

State Protection: Threatened
listed species are those with: 1) 6 to fewer than 20 extant sites, or 2) 1,000 to fewer than 3,000 individuals, or 3) restricted to not less than 4 or more than 7 U.S.G.S. 7 minute topographical maps, or 4) listed as threatened by U.S. Department of Interior.

Federal Protection: Not Listed

State Rarity Rank: S2S3
A State Rarity Rank of S2S3 means: Imperiled or Vulnerable in New York - Very vulnerable to disappearing from New York, or vulnerable to becoming imperiled in New York, due to rarity or other factors; typically 6 to 80 populations or locations in New York, few individuals, restricted range, few remaining acres (or miles of stream), and/or recent and widespread declines. More information is needed to assign a single conservation status.

Global Rarity Rank: G5
A Global Rarity Rank of G5 means: This species is demonstrably secure globally, though it may be quite rare in parts of its range, especially at the periphery.

Did you know?
Ulmus thomasii is known as "Cork Elm" for the distinctive corky ridges on its twigs and branches. It has the hardest and heaviest wood of the elm species, and is desirable for use in furniture, tools, and fence posts. Another common name, "Rock Elm", may refer to the hardness of the wood or to its preferences for rocky ridgetop habitats (Little 1979).

State Ranking Justification [-]
There are at least 15 existing sites, and about 50 historical sites, mostly known from the 1930s and before. Like our other elm species, Ulmus thomasii is threatened by Dutch Elm Disease.

Short-term Trends [-]

Long-term Trends [-]