Schiedea ligustrina is a dioecious shrub ranging from 30 to 60 cm tall. The stems are typically erect or strongly ascending, terete or 4-angled/ridged, and glabrous, with a green to greenish-purple coloration and nodes often swollen. Internodes measure 0.5–2.5 cm long. The leaves are simple and arranged oppositely, with blades varying from elliptic–oblanceolate to elliptic or linear. Leaf blades measure (2–)3–5(–6) cm in length and (0.2–)0.5–1.5 cm in width, with acute to mucronate apices and attenuated bases that may be connate around the stem. The yellowish-green blades are coriaceous with entire, somewhat thickened, and weakly revolute margins. Only the midvein is evident. Petioles are 0–0.6 cm long, winged, and may be weakly to conspicuously connate around the stem. Stipules are absent. Inflorescences are terminal and consist of 15–138 flowers measuring 4–15 cm long. They are congested, especially laterally, with staminate inflorescences typically broader and less congested than pistillate ones. The bracts on the central axis are 2–15 mm long; those on branches and flowers are 1–1.8 mm, green to purple, and linear to subulate. Pedicels are (1–)3–7(–10) mm long, quadrangular, and somewhat flattened. The flowers are unisexual, with plants being dioecious. Staminate flowers have 2.2–2.7 mm long sepals, narrowly ovate, navicular, reflexed at the base, and glabrous, with entire scarious margins and obtuse apices. Stamens number ten, with slightly dimorphic filaments: the antisepalous whorl is 3.1–4 mm long, and the alternate whorl is 2.9–3.6 mm long. Anthers are yellow and measure 0.7–0.9 mm. Pistillate flowers have similar sepals (2.1–2.3 mm) and ten vestigial stamens with unequal filaments (0.7–0.9 mm) and non-functional anthers (0.3–0.4 mm). The corolla is absent in both flower types. The fruits are narrowly ovoid capsules, 2–3.5 mm long. Seeds are relatively few, measuring 0.8–1.1 mm long, reniform, compressed, and papillose, with larger papillae along the margins. The perisperm is starchy and typically hard, with true endosperm absent. It is found in dry to diverse mesic forests between (180–)300–830 meters.