This shrub is 3-12' tall, often branching abundantly near the base, but with long unbranched stems above. The woody stems are yellow to reddish brown, while young shoots are light green and either glabrous or finely hairy. Alternate leaves about 2½-5" long and ½-1½" across occur along the woody stems and young shoots; they are lanceolate-oblong in shape and finely serrated along their margins. The bases of mature leaves are cordate to rounded. Young leaves are frequently copper-colored to red, while mature leaves are medium green above and whitened below. Young leaves are glabrous to finely hairy, while mature leaves are glabrous (or nearly so). The slender petioles are about ½-1" long and they lack minute glands near the blades. Pairs of leafy stipules often persist at the bases of petioles. These stipules are about ½" long with serrated margins; a pair of stipules are oval-cordate to reniform in outline. Heart-Leaved Willow is dioecious, producing staminate (male) catkins and pistillate (female) catkins on separate shrubs. These catkins are produced a little before or during the development of first-generation leaves during the spring. Staminate catkins are ¾-1½" long. Each floret of these catkins has 2 stamens. At the base of these stamens, there is a single finely hairy bract that is brown to black and a minute cylindrical gland. Pistillate catkins are 1-2½" long. Each floret of these catkins has a single lanceoloid ovary (4-6 mm. long) that is glabrous and a short style with divergent stigmata on top; there is a short pedicel underneath the ovary. Beside the pedicel, there is a single finely hairy bract that is brown to black and a minute cylindrical gland. Blooming period lasts about 1-2 weeks during the spring. Afterwards, the female florets are replaced by seed capsules that split open to release tiny cottony seeds. These seeds are distributed by the wind. The root system is shallow, woody, and branching. This shrub spreads by reseeding itself.