Helianthus tuberosus is a herbaceous perennial plant growing to 1.5–3 m (4 ft 11 in–9 ft 10 in) tall with opposite leaves on the upper part of the stem but alternate below. The leaves have a rough, hairy texture. Larger leaves on the lower stem are broad ovoid-acute and can be up to 30 cm (12 in) long. Leaves higher on the stem are smaller and narrower.
The flowers are yellow and produced in capitate flowerheads, which are 5–10 cm (2.0–3.9 in) in diameter, with 10–20 ray florets and 60 or more small disc florets.
The tubers are often elongated and uneven, typically 7.5–10 cm (3.0–3.9 in) long and 3–5 cm (1.2–2.0 in) thick, and vaguely resembling a ginger root in appearance, with a crisp and crunchy texture when raw. They vary in colour from pale brown to white, red, or purple.