It is a herbaceous perennial which grows annual stems about a meter tall bearing narrow green leaves and yellow flowers. Ginger is in the family Zingiberaceae, to which also belong turmeric (Curcuma longa), cardamom (Elettaria cardamomum), and galangal. Ginger originated in the tropical rainforest in Southern Asia. Although ginger no longer grows wild, it is thought to have originated on the Indian subcontinent. The ginger plants grown in India show the largest amount of genetic variation. The larger the number of genetic variations, the longer the plant is thought to have grown in that region. Ginger was exported to Europe via India in the first century AD as a result of the lucrative spice trade and was used extensively by the Romans.