ORYZA sativa var. rufipogon
Plant Common Name
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Arguably the world's most important crop, cultivated rice has been a staple of Asian diets for more than 7,000 years. This annual grass was probably first domesticated in Southeast Asia and southern China from wild populations of the perennial Oryza rufipogon. Rice is now cultivated and consumed globally, but the bulk of the world's crop still originates in Asia. The lower Mississippi Valley and north-central California are centers of rice production in the United States.
This rhizomatous grass forms spreading clumps of upright to arching stems lined with long, slender, smooth green leaves. Branching panicles of greenish flower "spikelets" appear at the stem tips, typically in summer. Each spikelet consists of a single, inconspicuous, wind-pollinated flower enclosed in a tough, ovoid, flat-sided husk. The flower matures to a hard-coated seed or rice grain, which easily separates from the husk. Unhulled spikelets (known as "paddy") are threshed or otherwise processed to separate the grain from the hulls. The vitamin-rich outer coating of the grain is typically polished off to convert it from "brown" to "white rice."
Rice needs ample water, sunlight, and soil fertility to grow successfully, but submerged soil is not necessary. Drought or frost kills this tender grass, and numerous tropical insects and fungi are problematic, especially in large monocultures. Sow seed in warm soil in late winter or early spring, either in the ground or in pots. Keep soil damp at all times. Plant out container-grown seedlings after danger of frost. A few selections of Oryza sativa are grown for ornament rather than for food; these include the purple-leaved cultivar 'Nigrescens'.
Rice plants serve numerous economic roles. Dried rice straw is used in equatorial regions as house roof thatch, fuel, packing material and green fertilizer. Rice grain hulls may be used for cellulose. The grains, rich in starch, readily absorb water as well as any flavors in the water, making them an excellent food staple. They may also be ground into flour, or distilled to make wine.
Several different races of rice exist, including the long-grain indica and short-grained sativa (or japonica) types. Numerous dwarf and semi-dwarf rice varieties have been introduced.
Grains commonly known as "wild rice" belong to other plant genera such as Zizania.