This shrub is 8-20' tall, sending up multiple branching stems that form a vase-shaped crown. Stems at the base of this shrub are up to 8" across. The bark of large old stems is gray to gray-brown, somewhat rough-textured, slightly shredded, and sometimes shallowly furrowed. The bark of young stems is gray to brown and smooth, while new shoots are green and glabrous. Pairs of opposite leaves occur along the young stems and shoots. Individual leaves are 2-5" long and 1½-3½" across; they are cordate to ovate and smooth along their margins. The upper leaf surface is yellowish green to dark green and hairless, while the lower surface is pale green and hairless. The slender petioles are ½-1½" long, light green, and glabrous. Elongated panicles of flowers about 3-7" long develop from the stems of the preceding year. The panicles taper gradually toward their apices and they are ascending to erect. Individual flowers are about 1/4" (6 mm.) across and 1/3" (8 mm.) long, consisting of a narrowly tubular corolla with 4 spreading lobes, a short tubular calyx with 4 teeth, a pistil with a single style, and 2 inserted stamens. On different shrubs, the corollas can be purple, lavender, light blue, pink, or white, although lavender is the most common color. The branches of each panicle are light green and glabrous.