Urera kaalae is a long-lived perennial small tree or shrub, 3–7 m tall, distinguished by their absence of stinging hairs. Their stems are characterized by copious sap that turns greenish black upon exposure to air, with weak, hollow, spreading branches that are glabrous and have pale brown bark. Leaves are simple, alternate, cordate, and somewhat asymmetrical, measuring 10–27 cm long by 5–13 cm wide, with those on young shoots sometimes extending up to 40 cm and petioles up to 24 cm long; seedling leaves are ovate and very coarsely serrate. The apex is acuminate, the base deeply cordate, surfaces sparsely covered with reddish resinous glands and initially densely short-hirtellous, becoming sparsely short-hirtellous along the veins on mature leaves, pale green, thin, and membranous. Margins are irregularly crenate-dentate, with palmately 3–5-veined at the base and 5–7 pairs of additional pinnate veins. Petioles are 4–13.5 cm long, glabrate, with connate and intrapetiolar stipules, lanceolate, 2–2.3 mm long, ciliate. Flowers emerge in basically trichotomous, open, paniculate cymes, with staminate cymes arising horizontally from lower leaf axils, 7–13 cm long, and pistillate cymes stiffer, ascending above upper leaves, 14–24 cm long. The plant is dioecious or monoecious with unisexual flowers; the calyx of staminate flowers is depressed-globose, sparsely covered with reddish glands, lobes ovate-deltate, 1.5–1.7 mm long; the pistillate calyx is green, laterally compressed, with lobes 3–5, ovate, unequal. No corolla (petals) present; staminate flowers have white filaments and dithecal anthers; pistillate flowers have a superior ovary, one basal ovule, and a large stigma. The fruit is an ellipsoid achene, strongly compressed, 0.8–1 mm long, half-enclosed by slightly enlarged and fleshy calyx lobes, with one seed per achene. It is found on slopes and gulches in diverse mesic forests between 300–760 meters.