The number of named species varies from 1 to about 16, the delineations based on differences in the amount, kind, and distribution of pubescence on leaves and twigs. For simplicity, we will follow the interpretation that the genus in eastern North America is composed of a single highly variable species, Tilia americana. It has a long, clear, somewhat buttressed bole, and a spreading root system. Leaves Leaves are simple, alternate, and deciduous. Leaf bases are irregular, some are equilateral, others inequilateral.
Leaf margins are serrate.
Leaf surfaces are dark green above, paler below, often with whitish, grayish, tan or brown pubescence. The flowers of this tree are perfect, yellow, and are in clusters on drooping, pubescent stalks, which are suspended from a leaf-like bract. The twigs are slender, sometimes zigzagging, pubescent at first, becoming glabrous. The pith is white and homogeous. The bark is thick, gray to brown or reddish-brown, deeply furrowed, with flattened ridges.