Arnoglossum reniforme is a tall and robust perennial forb, which reaches a height of 1-3 m (3-10 ft.). Plants are often observed with multiple stems arising from the same root-crown. The stem is ridged to angulate and usually glabrous. The plant has large basal leaves, often the size of a dinner plate; the petioles are up to 30 cm (12 in.) long; blades are reniform or ovate-cordate and >40 cm (>16 in.) long, with 3-5 main veins and lobed or dentate margins. Cauline leaves are proximal and petiolate, with margins entire, serrate, or dentate. Leaves are green on both sides. The inflorescence is a flat-topped umbel, with numerous heads. The flowers are white to cream or greenish and cylindrical in shape.