T r e e s  o f  N o r t h  C a r o l i n a

Ulmus L. (Ulmaceae)

A genus of about twenty-five to thirty species of trees (rarely shrubs); temperate and boreal regions of the Northern Hemisphere (most diverse in c. and n. Asia).

Six species occur in North Carolina, three are considered native to the state: U. alata (Winged elm), U. americana (American elm), and U. rubra (Slippery elm).

Key to Ulmus in North Carolina

1. Leaf blades mostly < 7 cm long, the base symmetrical to somewhat oblique...2.

2. Samaras ciliate-margined; twigs often cork-winged; upper surfaces of leaves glabrous to scabrous; [native trees, sometimes weedy]...U. alata (Winged elm)

2. Samaras with glabrous margins; twigs never cork-winged; upper surfaces of leaves glabrous; [introduced trees, planted and sometimes naturalized or persistent]...3.

3. Mature bark smooth or scaly with orange blotches; flowers appearing in the late summer to fall; leaf base generally oblique; leaves 1.5-2.5 cm wide, 5 or more of the lateral veins forked per side...*U. parvifolia (Chinese elm)

3. Mature bark distinctly ridged, not scaly; flowers appearing in the late winter to late spring; leaf base generally symmetrical; leaves 2-3.5 cm wide, 3 or fewer of the lateral veinsforked per side...*U. pumila (Siberian elm)

1. Leaf blades mostly > 7 cm long, the base moderately to strongly oblique (rarely nearly symmetrical)...4.

4. Leaf uppersurface glabrous (or slightly to moderately scabrous on stump sprouts or seedlings); leaf undersurface glabrous to tomentose, with or without tufts of hairs in the vein axils; flowers and fruits pedicellate (on pedicels 5-20 mm long), pendulous, in fascicles or racemes...U. americana (American elm)

4. Leaf uppersurface slightly to very strongly scabrous; leaf undersurface tomentose or villous, with tufts of hairs in the vein axils; flowers and fruits sessile or subsessile (on pedicels 0-2 mm long), not pendulous, in dense fascicles...5.

5. Leaves without ciliate margins; samara glabrous except along the margin of the notched apex or on the central vein of the wing; bud scales brown, margins pale-cilate; [introduced tree, planted and sometimes naturalized or persistent]...*U. minor (English elm)

5. Leaves with ciliate margins; samara pubescent on the body with reddish hairs; bud scales red, the margins red-tomentose; [native tree]...U. rubra (Slippery elm)