Leaf shape, while often a distinctive identifying feature of trees, can also be confusing when many trees share leaves of similar shape.
In separate articles we discuss oaks and maples and the most common shape, the roughly oval leaves borne by a number of species, from birch to beech and onward. Here we address other shapes taken by simple leaves, that is, those with one leaflet per leaf stem, as opposed to compound leaves, which have many leaflets on a single stem.
Quaking Aspen: Relatively small leaves with fine teeth and a sharp terminal point. Leaf stems are flat. Bark is off-white, often mistaken for white birch but slightly darker, with chalky texture. Leaves tremble rapidly in the slightest breeze and make a particular kind of rattling noise.
Cottonwood: Leaves similar to aspen but larger and with coarser teeth. Leaf stems flat. Bark is smooth and pale when young, becomes vertically furrowed when older. Bears long, elegant strings of brownish flowers in early spring. Later in the spring they mature to release cottony seeds that may resemble snow when scattering on the wind.
Basswood / Linden: Coarsely toothed leaves with irregular bases. Flowers and seeds are borne individually on bracts, leaflike structures shaped, in this case, like small tongue depressors. Buds are dark reddish, gooey when chewed. Basswood is the American species, with several regional variants. Several European varieties, known as Lindens, are often planted in cities and bear profuse and fragrant, creamy white flowers in June.
Paulownia (Princess-tree): Large leaves, the size of an adult’s hand, in opposite arrangement. Its clusters of purple flowers appear in mid-spring. Tan seed pods are the size and shape of pecan hulls. Asian import. See Paulownia blog.
Catalpa: Leaves similar to Paulownia, but some leaves are opposite and others are whorled (3 or more leaves meeting at the twig). Flowers appear in late spring, frilly white with purple speckles and yellow patches. Seed pods are dark brown, narrow, and up to a foot long.
Lanceolate (Long and Narrow)
Black cherry (wild cherry): Leaf has fine teeth, pointed tip. Along base of midrib on underside of leaf are tiny hairs, white when young, turning rust-brown in summer. Inner bark of twig has a smell of bitter almond. Edible, burgundy-colored fruits turn almost black when ripe in late summer.
Willow: Many varieties, some with toothed leaves and others smooth-edged. Often shrubby, with flexible trunks. Grows in damp areas, useful for preventing erosion.
Willow Oak: The only oak with lanceolate rather than lobed leaves. Bears acorns like other oaks.
Tulip-tree (yellow poplar): Roughly rectangular leaf with four flaring lobes. Large, green, tulip-shaped flowers with orange parts, yielding to tan, cuplike seed-containing skeletons that stay on trees in winter. A tall tree with furrowed bark resembling that of ash.
Mulberry: Irregular, variable leaf shapes. Yields sweet fruit in early summer, like elongated raspberries, in black or white.
Sassafras: Three leaf shapes on a single tree: oval, mitten-shaped, and three-lobed. Inner bark. leaves, and yellow spring flowers are aromatic.
Sweetgum: Star-shaped, five-lobed leaves, distinctive round, prickly seed pods.
Sycamore: Leaves lobed, resembling those of maple. Bark variegated in green, white, tan patches. Seeds in balls that hang from twigs.