The Bald Cypress is a large slow-growing and long-lived tree typically reaching 100 to 120 ft with a trunk diameter of 3 to 6 ft. The bark is gray-brown to red-brown, thin and fibrous with a stringy texture, having a vertically interwoven pattern of shallow ridges and narrow furrows. The leaves are alternate and linear, with flat blades borne on the twig that are spirally arranged on the stem, but twisted at the base to lie in two horizontal ranks. Unlike most other species in its family, it is deciduous, losing its leaves in the winter months, hence the name ‘bald’.
Bald cypress trees growing in swamps have something called cypress knees. These are woody projections from the root system project above the ground or water. Their function was once thought to be to provide oxygen to the roots, which grow in the low dissolved oxygen waters typical of a swamp (as in mangroves). However, evidence for this is scant; in fact, roots of swamp-dwelling specimens whose knees are removed do not decrease in oxygen content and the trees continue to thrive. Another more likely function is structural support and stabilization. Bald cypress trees growing on flood-prone sites tend to form buttressed bases, but trees grown on drier sites may lack this feature. Buttressed bases and a strong, intertwined root system allow them to resist very strong winds; even hurricanes rarely overturn them.
The tallest known individual specimen is in Virginia and the widest in Louisiana. The oldest is in North Carolina — over 1,620 years old, making it one of the oldest living plants in eastern North America.