Birch (_Betula spp._), hardy in U.S. Department of Agriculture plant hardiness zones 3 to 9, depending on species, and aspen (_Populus spp._) are both deciduous trees with light-colored thin bark and leaves that turn yellow in autumn. Both are native to North America and are planted as ornamental landscaping trees. Despite their similarities, there are some characteristics that make it easy to distinguish them from one another.
Bark and Leaves
Paper birch (_Betula papyrifera_), also known by the common names of white birch and canoe birch, and trembling or quaking aspen (_Populus tremuloides_) are popular landscaping trees across the United States. Both have white bark. Birch bark turns lighter and peels off in sheets as the tree matures; aspen bark may become rough in older trees but does not peel off. Both aspen and birch have ovate, serrated leaves -- however aspen leaves are rounder than birch and more finely toothed.
Height and Life Span
Birch trees grow to 40 to 50 feet in height and can live for 40 to 50 years. Aspen typically reach 20 to 80 feet in height. Individual aspen trees live about 80 years in natural forests but may only survive 20 years in urban settings. Aspen grow naturally in colonies where all trees are clones connected by the roots. The colony can survive wildfire and other extremes because the root system is underground; one colony in Utah is estimated to be 80,000 years old.
Weeping birch (_Betula pendula_) is a European species that grows in a "weeping" habit. There is no weeping aspen species.
Quaking aspen is hardy in USDA zones 2 to 8 and does not tolerate shade. Birch requires sunlight on the foliage and cool, moist, shaded soil. Paper birch thrives in USDA zone 3 and will tolerate warmer climates. River birch (_Betula nigra_), also commonly known as red birch, does well in zones 4 to 6.
Gray birch (_Betula populifolia_), yellow birch (_Betula alleghaniensis_) and sweet, black or cherry birch (_Betula lenta_) are native to the northeastern United States and hardy in zones 3 to 6; river or red birch (_Betula nigra_), hardy in zones 4 to 9, is native to the South and grows as far north as Minnesota. Quaking Aspen grows all across North America, though it's most common in Colorado and Utah at elevations of 5,000 to 12,000 feet.
Birch trees grow from seed but can regenerate from sprouts after a tree has been cut down or burned in a wildfire. Aspen can grow from seed, but more commonly sprout from the roots.