Schiedea diffusa subsp. macraei is a reclining or weakly climbing vine. The primary stems of this vine are 3-6 (–10) meters long, usually swollen at the nodes, and can be terete or 4-angled or -ridged. These stems are glabrous or nearly so below but become antrorsely puberulent in the inflorescence, with reddish-purple hairs. The leaves are simple, opposite, and lanceolate to narrowly ovate or sometimes oblong-elliptic, measuring 6.5–8.9 cm in length and 1.5–2.5 cm in width. The leaf bases often encircle the stem, with the apex of the leaves being acute to attenuate and the base ranging from acute to broadly obtuse. The leaf blades are coriaceous and green to yellowish green, with only the midvein prominently visible. The inflorescence comprises 65–73 cleistogamous, bisexual (perfect) flowers, extending 10–50 cm long. The pedicels are 14–24 mm long at anthesis and slightly elongate in fruit. Sepals measure 4.3–4.7 mm in length, while petals are absent. The staminal filaments are dimorphic, and the ovary is superior, 1-celled, with free-central placentation. The fruit is an ovoid-globose capsule 4.5–5 mm long, containing numerous seeds that are 1–1.2 mm long, suborbicular, and asymmetrical. The seeds’ surface is smooth but shows minute depressions under high magnification, and they persist on the placenta within the un-dehisced capsule. The perisperm (a layer of nutritive tissue that surrounds the embryo of a seed) is starchy, with true endosperm absent. It is often found in wet montane forests between 1000–1220 meters.