It is similar in appearance to the green ash, making identification difficult. These include poplars, willows, red maple, silver maple and green ash. The natural habitat of green ash is almost exclusively stream sides and bottomlands. The woods consist of sweetgum, sugar maple, tuliptree, shumard oak, and green ash throughout. The understory is composed of ironwood, green ash, and aspen. The most common trees are cedar elm, pecan and green ash. They include American elm, basswood, cottonwood, green ash, bur oak, hackberry and box elder. Black ash commonly occurs in swamps, often with the closely related green ash. Green ash and black ash trees are preferred by emerald ash borer. About 40% of boulevard trees in Edmonton, Alberta are green ash. Green ash is threatened by the emerald ash borer, a beetle introduced accidentally from Asia.