Lobelia dunbariae subsp. paniculata is a shrubby plant characterized by its woody, decumbent stems, which typically range from 30 to 80 cm in length and are leafy in the upper half. The leaves are simple and alternate, with blades that are linear or narrowly elliptic, measuring 8–20 cm long and 0.5–2 cm wide. The leaf apex is acute to acuminate, and the surfaces are glabrous and slightly paler on the lower side. The margins are minutely callose–denticulate and flat, and the leaves are sessile to subsessile, with no stipules present. The flowers are arranged in inflorescences that are 2–6–branched at the base, measuring 15–25 cm long. Pedicels are 8–12 mm long and glabrous, with either linear and 12–15 mm long bracts or narrowly elliptic and 30–60 mm long. The hypanthium is obconical, measuring 4–10 mm in length. The flowers are bisexual (perfect), with calyx lobes that are 3–5 mm long and sepals that are connate, with the tube adnate to the ovary. The corolla is zygomorphic (bilaterally symmetric), dorsally cleft almost to the base, and blue, measuring 18-26 mm long and 3-4 mm wide. The lobes of the corolla are spirally revolute, and the tube is suberect. The stamens number five and alternate with the corolla lobes. The staminal column is sparsely pubescent, and the anthers are glabrous, but the lower two have apical tufts of white hairs. The anthers are dithecal, opening by longitudinal slits, and are coherent but separate after anthesis or are connate, forming a tube for pollen shedding. The filaments are either distinct or connate above, attached to the epigynous nectary disk or the base of the corolla, and rarely adnate to the corolla tube. The fruit is an ovoid capsule measuring 6–12 mm long, dehiscent at the apex by two valves. It contains numerous brownish seeds, each approximately 0.5 mm long, smooth, with a straight, short to spatulate dicotyledonous embryo embedded in oily endosperm. It inhabits cliffs in wet forests on Moloka’i between 1,000-1,200 meters.