Ulmus americana 'Jefferson'
Common Name: American elm
Type: Tree
Family: Ulmaceae
Zone: 5 to 9
Height: 40.00 to 50.00 feet
Spread: 40.00 to 50.00 feet
Bloom Time: March to April
Bloom Description: Green
Sun: Full sun
Water: Medium
Maintenance: Low
Suggested Use: Shade Tree, Street Tree, Rain Garden
Flower: Insignificant
Tolerate: Drought, Black Walnut, Air Pollution

Culture

Grow in average, medium moisture, well-drained soils in full sun. Tolerant of light shade. Prefers rich, moist loams. Adapts to both wet and dry sites. Generally tolerant of urban conditions.

Regular pruning and spraying is advisable because of Dutch elm disease threat.

Noteworthy Characteristics

Ulmus americana, commonly called American elm, is a medium to large deciduous tree, typically growing to 60-80’ (less frequently to 130’) tall with a vase-shaped, broad-rounded crown. It is native to eastern and central North America. In Missouri, it typically occurs in low moist ground and along streams throughout the state (Steyermark). Although once widely planted as a street and lawn tree, American elm populations have been so decimated by Dutch elm disease that this tree is no longer considered to be a viable selection for landscape uses. Insignificant small green flowers appear in spring before the foliage emerges. Flowers give way to single-seeded wafer-like samaras (each tiny seed is surrounded by a flattened oval-rounded papery wing). Seeds mature in April-May as the leaves reach full size. Rough-textured, ovate-elliptic, dark green leaves (to 6” long) have toothed margins and asymetrical bases. Leaves typically turn an undistinguished yellow in fall.

Genus name comes from the Latin name.

Specific epithet means of North or South America.

'Jefferson' reportedly has excellent resistance to Dutch elm disease and is currently being planted. It was released by the National Park Service and Agricultural Research Service in 2005. It was reportedly cloned in 1993 from an elm on the National Mall in Washington D.C. that has survived since the 1930s. It typically grows to 50' tall and as wide.

Problems

'Jefferson' has excellent resistance to Dutch elm disease. It is susceptible to phloem necrosis a disease caused by a phytoplasma that attacks the food-conducting tissue of the tree, usually resulting in a loosening of the bark, wilting, defoliation and death. It is also susceptible to wetwood which is a bacterial disease that results in wilting and dieback. Various wilts, rots, cankers and leaf spots may also occur. Insect visitors include borers, leaf miner, beetles, mealy bugs, caterpillars and scale.

Garden Uses

May be used as a lawn, shade or street tree.