The American elm tree once was a common sight across most of the eastern United States. The American elm had a range from Nova Scotia down the Atlantic Coast to central sections of Florida. It grew as far west as Texas and the Dakotas. Unfortunately, the elm fell victim to a disease that now leaves few mature elms in a state of good health. Take heart, however--disease-resistant cultivars of the elm still exist.
Dutch elm disease is the ailment responsible for the demise of the majority of American elm trees. An insect called the elm bark beetle transmits the fungal disease to the tree. Dutch elm disease prevents much-needed nutrients and water from getting to different parts of the tree. It accomplishes this by clogging up the vascular system of the elm. The young elm trees will often reach the stage where they reproduce before the disease affects them. However, according to the Ohio Department of Natural Resources website, the disease commonly strikes once an elm tree attains a height of around 40 feet.
The healthy American elm tree normally has a shape resembling a vase, with the trunk extending up into a canopy of branches that spread outward from the tree. The elm has the capability to reach between 60 and 90 feet, with a spread of branches that often is wider than the tree is tall. The trunk of the unaffected mature specimen ranges between 2 and 4 feet in width.
Elm leaves are between 3 and 6 inches in length and have asymmetrical bases, meaning one side where the stem attaches to the leaf is a bit higher than the other side. The edges of an elm leaf have serrations like teeth. The lower surface of an elm leaf is typically slightly hairy. Approximately 15 pairs of branching veins exist on an elm leaf, extending outward from a middle vein that develops the length of the leaf. Elm leaves are a dark green but turn to shades of yellow or chartreuse in autumn.
Elm trees will grow to their greatest potential in rich fertile ground. Keep the soil damp when you transplant an elm tree until the tree establishes its root system. The pH level of the soil should not be a factor when it comes to elm trees. Place your elm in a spot where it will get full sun throughout the day.
Choose a cultivar of the American elm designed to resist Dutch elm disease for your landscaping needs. The University of Connecticut Plant Database website states that a hybrid called Delaware #2 has shown it can resist Dutch elm disease and this species will grow to 80 feet high. The National Park Service developed a cultivar known as Jefferson that exhibits the classic vase shape of the elm and grows to 50 feet. One cultivar, called Valley Forge, has proven very resistant to the Dutch elm disease and the tree attains heights of 70 feet, with a spreading canopy 60 feet wide.