Betula populifolia the female catkins erect. The fruit, maturing in autumn, is composed of many tiny winged seeds packed between the catkin bracts. The wood is medium hard and is used for high grade plywood, furniture, drum shells, spools and firewood. Like other North American birches, gray birch is highly resistant to the Bronze birch borer ("Agrilus anxius"). The leaves of the gray birch serve as food for various Lepidoptera, such as the leaf miner moth "Cameraria betulivora". Between about 1930 and 1950, many gray birch trees, along with paper birch and yellow birch ("Betula alleghaniensis"), were affected and killed by birch
Betula lenta male catkins pendulous, the female catkins erect. The fruit, maturing in fall, is composed of numerous tiny winged seeds packed between the catkin bracts. Seed production mainly occurs in trees that are between 40 and 200 years old, although light crops may occur as early as 15 years and as long as the tree lives. Contrary to common knowledge, the lifespan of "B. lenta" is typically around 200 years, and many individuals will reach 250 and even 300 years. The oldest known "B. lenta" has been confirmed to be 368 years old, and the species may live even longer than