www.ctahr.hawaii.edu/oc/freepubs/...FS-GIN-3A.pdf
Edible ginger is a herbaceous perennial plant that is grown as an annual in commercial production. It is cultivated in the tropical and subtropical regions of the world. Internationally, processed ginger "root" (rhizome) is the standard of commerce and is traded as a dried spice or candied. The harvest season varies by location, with northern hemisphere locations such as Hawaii having harvests that begin in December and southern hemisphere locations having harvests beginning in July.
The ginger plant grows from 2 to 4 ft (61-122 em) high under commercial conditions. Edible ginger is asexually propagated from a portion of the rhizome. The ginger rhizome grows horizontally in the wild and develops a greenish color when exposed to sunlight, due to chlorophyll development. Abundant rainfall, sunlight, and warm temperature are required throughout its growth cycle.