Curcuma longa aka Turmeric

Curcuma longa, or turmeric, is in the ginger family. This plant comes from the tropics and lives for years. It grows from rhizomes: thick, branched stems below ground. Kew lists it as a farmed plant from southwestern India. Its exact place of origin is still unclear. People have farmed it for thousands of years. No one knows of a true wild population. Some plants now grow wild after escaping from farms or gardens. Growers raise it in tropical and subtropical regions. Its rhizomes give foods a yellow-orange spice.

Plants grow in upright clumps with large, pleated green leaves. Garden plants reach 3–4 feet [0.9–1.22 metres] tall and wide. RHS gives a smaller spread of 0.3–1.6 feet [0.1–0.5 metres]. The short stems hold leaves in two rows. Leaves have pointed tips and oval to lance-shaped forms. Their tops are dark green; their undersides are paler green. The largest leaves reach about 3.5 feet [1.07 metres] long. Dense flower spikes hold pale yellow to yellow-white blooms. They bloom from July to August among cupped bracts. These are leaf-like parts around the flowers. The flowers are sterile and cannot make viable seeds. Gardeners divide the rhizomes to grow more plants. RHS says farmed plants cannot set fruit. NC State describes small brown seeds that cannot sprout.

Turmeric grows best with heat, damp air, and rich soil. Keep the soil moist, but let excess water drain. Outdoor plants suit morning sun and shade later that day. RHS advises bright light indoors, but not direct sun. Its soil guidance spans sand, loam, and broad pH levels. NC State favors mildly acid soil but also lists neutral soil. Missouri Botanical Garden lists USDA hardiness zones 8–11. RHS rates it H1A for warm, sheltered UK growing sites. Outside hardy areas, gardeners can grow it for one year. They can also dig up rhizomes for winter storage. Keep them in a cool, sheltered place. Plants in pots need plenty of water. Growing rhizomes may split pots when they lack space.

The bold leaves and summer blooms suit herb gardens and pots. Growers harvest rhizomes in fall when leaves start to dry. They boil, dry, and grind them to make turmeric powder. It gives food a bitter, pungent taste and yellow color. People can eat young shoots and rhizome tips raw or cooked. Rhizomes also give dyes for cloth and other things. People use turmeric in beauty products and traditional medicine. These uses do not prove that treatments are safe or work.

Serious pests and plant diseases rarely cause problems. Dry soil can favor spider mites. Slugs and snails harm young leaves. Plants need no set pruning beyond removing old, yellow stems. Cut rhizomes can leave lasting stains on skin and cloth. Contact can also cause an allergic skin rash in some people.