Schiedea lychnoides is a weakly climbing or sprawling vine. The stems are often swollen at the nodes, terete (cylindrical), 4-angled, or ridged, with primary stems reaching up to 3 meters long and featuring short lateral branches. The leaves are simple and opposite, with ovate to elliptic blades measuring 4.5–6.5 cm long and 1.8–3.8 cm wide. The leaf apex is mucronate, and the bases are often connate around the stem. The surfaces are sparsely puberulent, with erect to somewhat antrorsely appressed hairs that are translucent with a purple tinge. The hairs on the principal veins on the lower surfaces and margins are coarser and more appressed, measuring 0.25–0.5 mm long. The blades are thin and membranous, dark green with a purple tinge, and the margins are inconspicuously serrulate, at least in the distal half. There are 3 or 5 principal veins, with the outer pair usually weakly developed. The petioles are 0.2–0.7 cm long, and stipules are absent. The flowers are arranged in pseudoaxillary inflorescences, with usually 3–17 (up to 21) flowers. All parts are densely glandular-puberulent throughout, with translucent, purple-tinged hairs measuring 0.25–0.5 mm long. The bracts are foliaceous, measuring 14–24 mm long, and the peduncles are 18–25 mm long. The internodes of the lateral inflorescence branches are 2–14 mm long, and the pedicels are thinner, measuring 7–18 mm long. The flowers are bisexual (perfect) and adapted for bird pollination, with a pendent orientation. The calyx consists of 5 sepals, measuring 9–12 mm long and 5–6.5 mm wide, enlarging to 12–18 mm long and 7–9 mm wide in fruit. The outer sepals are larger and rhombic, while the inner ones are oblong-rhombic, greenish-white, thin, and membranous. At maturity, they become slightly recurved along the margin of the upper half of the outer pair, especially as the fruit develops, with an obtuse and mucronulate apex. The sepals are densely glandular-puberulent abaxially and glabrous adaxially. The corolla (petals) is absent. There are 10–13 stamens, with filaments measuring 5.5–6.3 mm long, the antisepalous ones being slightly longer to subequal. The anthers are 0.8–1.3 mm long, pale reddish purple at anthesis, changing to a darker reddish purple, and the pollen is pale gray. The ovary is superior and 1-celled, with free-central ovule placentation and 8–11 styles, often varying in number on the same plant. The fruit is an ovoid capsule measuring 9–12 mm long. The seeds are approximately 1.0 mm long, black, and persistent on the placenta, being released as the capsule gradually rots. The margins of the cells of the seed coat are slightly convex, with raised cells forming low transverse ridges across the seed surface. The perisperm is starchy and hard, with true endosperm absent. It is found in wet forests, often along streams, trailing on the ground, or sprawling over other vegetation between 1,090-1,320 meters.