Kratom (Mitragyna speciosa) is an evergreen tree that can grow to a height of 25 m (82 ft) tall and the trunk may grow to a 0.9 m (3 ft) diameter. The trunk is generally straight and the outer bark is smooth and grey. The leaves are dark green and glossy, and can grow to over 14–20 cm (5.5–7.9 in) long and 7–12 cm (2.8–4.7 in) wide when fully open, are ovate-acuminate in shape, and opposite in growth pattern, with 12–17 pairs of veins. The flowers grow in clusters of three at the ends of the branches. The calyx-tube is 2 mm (0.079 in) long and has 5 lobes; the corolla-tube is 2.5–3 millimetres (0.098–0.118 in) long.
Mitragyna Speciosa is indigenous to Thailand, Indonesia, Malaysia, Myanmar, and Papua New Guinea.