Fleshy subterranean roots called rhizomes give rise to herbaceous, fragrant stems and foliage on the turmeric plant (Curcuma longa). Growing in moist, warm soils that are rich in organic matter, turmeric typically goes dormant during the tropical dry season. Plant it outdoors in frost-free landscapes, such as in USDA winter hardiness zones 11 and warmer, in a partially shaded location under the dappled shade of trees.
Turmeric is a member of the ginger family, Zingiberaceae. It is placed in the genus Curcuma, which comprises 40 other species of tropical perennials that grow from rhizome roots.
Turmeric is native to the southern parts of India, where the climate seasonally rotates between long bouts of drought and wet monsoonal seasons.
The underground rhizomes are actually horizontal stems that store starches and have many fibrous roots that radiate outward into the soil. The rhizome produces "eyes" or growing points where upright, rigid but herbaceous stems grow 4 to 5 feet tall and bear long, broad lance-like leaves of deep green. The small white flowers that appear are in clusters of bracts (modified leaves) that are pale yellow. The foliage produces food that is transported to the roots, resulting in larger rhizomes as well as new branching structures. In chilly or dry weather, the foliage dies back to the ground, but the plant persists while dormant underground and resprouts when soil moisture and warmth return.
Crush any part of the turmeric plant, and an aroma of spice occurs. According to Online Curcuma Longa, this plant has been used in a culinary capacity in China since 3000 B.C. The dried rhizomes are pulverized into an orange powder that is coarse and is known as the spice turmeric. Further extraction of oils and moisture from turmeric yields curcumin, a golden yellow form of the polyphenols in the rhizomes that is 18 times more concentrated than in the spice turmeric form. These spices provide the yellow coloration of Indian curry powder and often are used to provide the deeper yellow color of the condiment mustard.
Both traditional and modern medicinal uses make the turmeric plant valuable as an agricultural crop. In India, uses for the spice powder included treating stomachache, skin ailments, muscular problems and arthritis. In China, it is often used as a topical analgesic and to treat colic, hepatitis, ringworm and chest pain. Poultices filled with turmeric or curcumin act to nullify pain and reduce inflammation. Modern research and medical uses, according to the U.S. National Library of Medicine, include potential for treatment against cancer and Alzheimer's disease. The compounds in this plant also warrant the current testing of effects on blood as well as manipulation of its anti-inflammatory, pain-killing and antimicrobial properties.