Ulmus americana Ulmaceae
American Elm UL-mus a-mer-i-KA-na
- Broadleaf deciduous tree, to over 75 ft (23 m), vase, arching branches (most common form), a spreading
form is also seen. Young shoots pubescent at first. Leaves alternate, simple, 7.5-15
cm, ovate-oblong, unequal at base, doubly serrate (toothed), glossy dark
green above, 13-18 parallel veins from midvein to the teeth. Flowers perfect, in groups of 3-4,
the anthers are bright red, the ovary and styles are light green, and the calyx is green tinged with red
above the middle; they appear in spring before the leaves. Fruit rounded, disc-like samara, about 12 mm long, greenish sometime with a
reddish tinge, maturing in early summer.
- Sun, prefers rich, moist, soils but grows under a variety of conditions.
- Once extensively used as a street and lawn tree. Dutch elm disease, which is caused by the
fungus Ophiostoma novo-ulmi through its transmission by the elm bark beetle, has changed that. Although no longer common in eastern North America,
there are several hundred American elms in Corvallis, most on the Oregon State campus. Newer selections of
Ulmus americana show moderate to high resistance to Dutch elm disease and are recommended for
planting. Many hybrid elms are also resistant to Dutch elm disease.
The term "Dutch" in the name of the disease is a reference to plant pathologists in the Netherlands who did
much early work on the disease.
- Hardy to USDA Zone 2 Native from Newfoundland to Florida, west to the
- Oregon State Univ. campus: tall, arching specimen on the northwest corner of the Valley Library quad,
lower spreading form directly west of library, and an intermediate form between these two. More
than 10 on the perimeter of the MU Quad.