Siam Queen is also known as Thai Basil and is a genus of flowering plants in the family Lamiaceae (mint family).The species are not clearly distinct and estimates of the number of species varies from 13 to 18. Siam Queen are aromatic, almost exclusively perennial, rarely annual, herbs. They have wide-spreading underground and overground branched stems. The leaves are arranged in opposite pairs, from oblong to lanceolate, often downy, and with a serrate margin. Leaf colors range from dark green and gray-green to purple, blue, and sometimes pale yellow.