is a tropical deciduous and evergreen tree in the coffee family (Rubiaceae) native to Southeast Asia in the Indochina and Malesia floristic regions. Its leaves are used for medicinal properties. It is psychoactive, and leaves are chewed to uplift mood. M. speciosa is indigenous to Thailand and, despite growing in the country, has been outlawed for 70 years and was originally banned because it was reducing the Thai government's tax revenue from opium distribution.
Kratom behaves as a μ-opioid receptor agonist like morphine and is used in the management of pain, as well as recreationally. Kratom use is not detected by typical drug screening tests, but its metabolites can be detected by more specialized testing. The pharmacological effects of kratom on humans, including its efficacy and safety, are not well-studied. M. speciosa has been associated with bowel obstruction, and the plant carries the potential for addiction and can lead to withdrawal symptoms.
It was first formally described by the Dutch colonial botanist Pieter Korthals. The genus was named Mitragyna by Korthals because the stigmas in the first species he examined resembled the shape of a bishop's mitre. It is botanically related to the genera Corynanthe and Uncaria and shares some similar biochemistry.
Mitragyna speciosa trees usually grow to a height of 12–30 ft (3.7–9.1 m) tall and 15 ft (4.6 m) wide, although some species can reach 40–100 ft (12–30 m) in height. Mitragyna speciosa can be either evergreen or deciduous depending on the climate and environment in which it is grown. The stem is erect and branching. The leaves of the kratom tree are a dark green colour and can grow to over 7 inches (180 mm) long and 4 inches (100 mm) wide, are ovate-acuminate in shape, and opposite in growth pattern. The flowers are yellow and round and tend to grow in clusters at the end of the branches. The leaves of M. speciosa are elliptic and are smaller at the end of the branchlets and are pointed at the tip. The leaves have a round and heart-shape at the base with the petioles between 2 to 4 centimeters long. The flowers are crowded in a round terminal inflorescences which are three to five centimeters long. The calyx-tube is short and cup-shaped, with round lobes. The corolla-tube is five millimeters long with three millimiter long lobes and smooth and revolute in between.