Schiedea jacobii is a perennial herb or subshrub characterized by a pale yellowish-green coloration throughout, particularly noticeable in cultivation. It typically grows to 40 to 76 cm, with stems often swollen at the nodes and conspicuously quadrangular, displaying either terete, 4-angled or -ridged forms. These stems are glabrous and range from ascending to sprawling, significantly longer. A fibrous root system supports the plant. The leaves are simple and opposite, with lanceolate to oblong-elliptic blades measuring 4.5 to 10.5 cm long and 1.4 to 2.6 cm in width. The leaf apex is acute to attenuate, and the base, often connate around the stem, ranges from acute to obtuse. The blades are coriaceous, with only the midvein evident, and the margins are slightly thickened and weakly revolute. The midvein is slightly eccentric. The petioles are 0.4 to 0.8 cm long, often flared at the juncture with the stem, with the leaf pair slightly connate. Stipules are absent. The inflorescence is terminal, bearing 10 to 70 flowers and measuring 40 to 50 cm long. It is weakly diffuse, with lateral branches 11 to 18 cm long, each bearing 25 to 35 flowers. The bracts are yellowish-green and foliaceous, with those in the lower portions of the central axis and lateral branches nearly as large as the leaves. The bracts in the upper part of the inflorescence and subtending the flower are narrowly lanceolate to subulate. The pedicels are 3 to 8 mm long at anthesis, elongating slightly in fruit but not exceeding 9 mm. The flowers are bisexual (perfect) and facultatively autogamous (self-fertilizing), with sepals measuring 3.9 to 4.2 mm long, lanceolate, and dull yellowish-green. The corolla (petals) is absent. Ten stamens with weakly dimorphic filaments and subequal yellow anthers dehisce after the flower opens. The ovary is superior, 1-celled, with free-central ovule placentation and 3 to 5 styles. The stigmas are receptive when the flower opens. The fruit is an ovoid capsule measuring 3.7 to 4.2 mm long, with approximately 16 to 22 seeds per capsule. The seeds are 0.9 to 1.2 mm long, suborbicular, asymmetrical, compressed, and brown. They remain coherent as a unit and persist on the placenta after dehiscence of the capsule, eventually dispersing or possibly germinating in situ in the wild. The seed surface is rugose, with starchy perisperm (nutritious layer surrounding the embryo) and absent true endosperm. It was found in wet montane forests around 1,930 meters.