Turmeric (Curcuma longa) is a tropical plant in the zingiberaceae, or ginger, family. Its fleshy orange rhizomes are dried to make the spice turmeric, which is known to have medicinal properties. Turmeric has been used for more than 4,000 years in India as a food ingredient and as a source of yellow and orange dyes. It is not a widely cultivated garden plant because it requires hot and humid conditions all year but is widely grown as a crop plant in tropical Asia.
Turmeric is a perennial plant with lanceolate, tapered leaves up to 2 feet long that have defined veins but a smooth surface. The leaves grow erect from a central stem growing out of the underground, fleshy rhizome. The branching rhizome has a smooth, brown skin and is bright orange on the inside. The small, yellow flowers are tubular and grow on a long spike with large green bracts. Flowering starts at the bottom of the spike and moves upward. Turmeric plants can grow up to 5 feet high.
Turmeric is known only as a cultivated plant, and its exact native range is unknown. It probably came from the tropical lowland zones of India and South Asia or Southeast Asia.
Cultivated plants thrive in semi-shaded conditions under trees in hot and humid tropical areas with acidic soils. The original wild plant was likely a tropical species that grew on the forest floor.
Turmeric plants need hot, humid conditions are are probably best suited to a greenhouse in nontropical gardens. They require temperatures between 85 and 95 degrees Fahrenheit and free-draining, acidic soil. Turmeric plants will not grow in full sun, and they do best in the high shade provided by trees. Propagation is by division of the rhizomes, as turmeric plants never seem to set seed. Fresh root, acquired in specialist food stores, should be soaked for 24 hours to remove any growth inhibitors and then planted in damp, peaty compost at a depth of about 2 inches. Turmeric plants are said to deter ants from the garden.
The shoots and young leaves from turmeric plants are used in Indonesia as a flavoring, and the rhizomes can be sliced and pickled or used fresh instead of ginger. The boiled, dried and ground rhizomes yield turmeric powder. This is bright orange, smells slightly of ginger and orange peel and has a warming, bitter flavor. It is widely used to color and flavor food in Asia and was known in medieval Europe as Indian saffron. Turmeric powder is a staple ingredient of Indian, Indonesian and Nepalese curry powders and pastes and is used widely in Iranian recipes. As a food additive and coloring agent, turmeric receives the code E100.
Traditionally, turmeric powder has been used in Asia to protect the skin from the sun, to even out blemishes and to disinfect cuts. It is also used to treat liver problems and to purify the blood. Turmeric has attracted a lot of attention from researchers and is known to have high levels of antioxidants. Turmeric has been found to have anti-tumor, anti-inflammatory, and anti-bacterial properties in laboratory tests The American Cancer Society states that curcumin, the active ingredient in turmeric spice powder, is capable of slowing down the growth of and even killing cancer cells in the lab. Human trials are still in the early stages.