Schiedea jacobii is a pale yellowish green perennial herb or subshrub with 40 to 74 cm (16 to 30 in) fleshy, long stems, ascending to sprawling when longer. Opposite leaves are 4.5 to 10.5 cm (1.8 to 4 in) long and 1.4 to 2.6 cm (0.6 to 1 in) wide, lanceolate to oblong-elliptic. Hermaphroditic, open flowers occur in terminal, branched inflorescences 40 to 50 cm (15.7 to 19.7 in) long, each with between 25 to 30 yellowish green flowers. Capsule is ovoid, 3.7 to 4.2 millimeters (mm) (0.15 to 0.16 in) long with 16 to 22 rugose seeds.