spinach (Spinacia oleracea) is a leafy green flowering plant native to central and western Asia. It is of the order Caryophyllales, family Amaranthaceae, subfamily Chenopodioideae. Its leaves are a common edible vegetable consumed either fresh, or after storage using preservation techniques by canning, freezing, or dehydration. It may be eaten cooked or raw, and the taste differs considerably; the high oxalate content may be reduced by steaming.

It is an annual plant (rarely biennial), growing as tall as 30 cm (1 ft). Spinach may overwinter in temperate regions. The leaves are alternate, simple, ovate to triangular, and very variable in size: 2–30 cm (1–12 in) long and 1–15 cm (0.4–5.9 in) broad, with larger leaves at the base of the plant and small leaves higher on the flowering stem. The flowers are inconspicuous, yellow-green, 3–4 mm (0.1–0.2 in) in diameter, and mature into a small, hard, dry, lumpy fruit cluster 5–10 mm (0.2–0.4 in) across containing several seeds.

In 2018, world production of spinach was 26.3 million tonnes, with China alone accounting for 90% of the total.

Etymology
Originally from Persian aspānāḵ, entering into the European languages by way of Latin, which received it from Arabic. The English word "spinach" dates to the late 14th century from espinache (French: épinard).

Taxonomy
Common spinach (S. oleracea) was long considered to be in the family Chenopodiaceae, but in 2003 that family was merged into the Amaranthaceae in the order Caryophyllales. Within the family Amaranthaceae sensu lato, Spinach belongs to the subfamily Chenopodioideae.

Nutrients
Raw spinach is 91% water, 4% carbohydrates, 3% protein, and contains negligible fat. In a 100 g (3.5 oz) serving providing only 23 calories, spinach has a high nutritional value, especially when fresh, frozen, steamed, or quickly boiled. It is a rich source (20% or more of the Daily Value, DV) of vitamin A, vitamin C, vitamin K, magnesium, manganese, iron, and folate. Spinach is a moderate source (10-19% of DV) of the B vitamins, riboflavin and vitamin B6, vitamin E, calcium, potassium, and dietary fiber (table). Although spinach is touted as being high in iron and calcium content and is often served and consumed in its raw form, raw spinach contains high levels of oxalates, which block absorption of calcium and iron in the stomach and small intestine. Spinach cooked in several changes of water has much lower levels of oxalates and is better digested and its nutrients absorbed more completely. In addition to preventing absorption and use, high levels of oxalates remove iron from the body.

Vitamin K
A quantity of 100 g of spinach contains over four times the recommended daily intake of vitamin K (table). For this reason, individuals taking the anticoagulant warfarin – which acts by inhibiting vitamin K – are instructed to minimize consumption of spinach (as well as other dark green leafy vegetables) to avoid blunting the effect of warfarin.

Production, marketing, and storage
Spinach production - 2018
Country Production
(millions of tonnes)
China 23.8
United States 0.38
Japan 0.23
Turkey 0.23
World 26.3
Source: UN Food & Agriculture Organization, Statistics Division (FAOSTAT)
In 2018, world production of spinach was 26.3 million tonnes, with China alone accounting for 90% of the total.

Fresh spinach is sold loose, bunched, or packaged fresh in bags. Fresh spinach loses much of its nutritional value with storage of more than a few days. Fresh spinach is packaged in air, or in nitrogen gas to extend shelf life. While refrigeration slows this effect to about eight days, fresh spinach loses most of its folate and carotenoid content over this period of time. For longer storage, it is canned or blanched or cooked and frozen.

Some packaged spinach is exposed to radiation to kill any harmful bacteria. The Food and Drug Administration approves irradiation of spinach leaves up to 4.0 kilograys, having no or only a minor effect on nutrient content. Spinach may be high in cadmium contamination depending on the soil and location where the spinach is grown.