(Zingiber officinale) Ginger root is the rhizome or underground stem of this Asian plant. Ginger root can be harvested at any time, but plants require several months of hot and fairly humid conditions to make the maximum yield. Plants may reach 4 feet in height. Mature roots are plump and sleek outside, white, juicy and aromatic within. May be grown outdoors in full sun in most of the country, lifting mature roots before ground freezes in autumn. Replant smaller roots next spring, preferably starting early in a sunny windowsill or greenhouse. 2 plants.