Ulmus americana 'Lewis & Clark' PRAIRIE EXPEDITION

Common Name: American elm 
Type: Tree
Family: Ulmaceae
Zone: 3 to 9
Height: 55.00 to 60.00 feet
Spread: 35.00 to 40.00 feet
Bloom Time: March to April
Bloom Description: Reddish-green
Sun: Full sun
Water: Medium
Maintenance: Medium
Suggested Use: Shade 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.

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.

‘Lewis & Clark’ was released and named in honor of the 200th anniversary of the Lewis & Clark Expedition in 2004 and is sold under the registered trade name of PRAIRIE EXPEDITION®. It is a medium to fast growing tree with the typical umbrella-like form of the American elm and lustrous dark green foliage. It is an outstanding Dutch elm disease resistant selection that is the lone survivor among American elm trees that died from Dutch elm disease along the Wild Rice River southwest of Fargo, ND. It is suitable for boulevard, park plantings and other large open spaces.

Problems

Dutch elm disease, a fatal fungal disease spread by airborne bark beetles, attacks the water-conducting tissue of the tree, resulting in wilting, defoliation and death. Phloem necrosis is 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. Wetwood 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.

PRAIRIE EXPEDITION® has outstanding resistance to Dutch elm disease.

Garden Uses

Street or shade tree.