American Elm, once a stately and magnificent tree that lined America's city streets, has partly followed in the footsteps of the American Chestnut, with many large American Elms succumbing to Dutch Elm disease. This pathogen (transmitted by the elm bark beetle) plugs the vascular system of the tree, preventing the flow of water and nutrients and slowly killing it. However, young trees are immune to the disease, and many reach reproductive age before falling victim to this foreign fungus.
Also known as White Elm (probably in reference to the creamy white wood), this large, vase-shaped tree is native to the entire eastern and central portions of the United States, extending into southern Canada. It is found throughout all of Ohio, primarily in moist sites such as bottomlands and ravines, but commonly seen in open fields, fencerows, and open woodlots, where the ground is dry in summer. Its arching canopy is majestic at maturity, but most trees now die by the time they reach 40 feet tall. Individual specimens, isolated from other Elms, may reach 80 feet tall by 60 feet wide. As a member of the Elm Family, it is related to Hackberry, Zelkova, and the numerous other Elms.
Planting Requirements- American Elm prefers moist, deep, rich soils of variable pH, but can tolerate soils that are dry and of average composition. Its winged seeds readily disperse over a wide area in spring, and the root structure of seedlings is initially taprooted, but quickly develops into a fibrous system that transitions to shallow roots with age (as is typical of species that like moist soils). It thrives in full sun to partial sun, and is found in zones 3 to 9.
Potential Problems- American Elm has been devastated by infection with Dutch elm disease, and fully mature specimens are getting harder to find. Isolation of trees (to reduce the spread of the fungus from infected trees, transmitted by both flying beetles and by roots that can graft between adjoining trees) is the best first line of defense, followed by annual spraying programs.
American Elm is also subject to elm phloem necrosis, which has symptoms similar to Dutch elm disease. In addition, the Elms in general are subject to numerous pests and pathogens which adversely impact their foliage, bark, wood, and roots, with the effects ranging from seasonal cosmetic blemishes, to serious threats to tree health.