Spinach, a plant of the chenopodiacew or goosefoot family, Spinacia oleracea, the leaves of which are used as food. According to some authors, the botanical and common names are derived from the Latin spina, a thorn, as some varieties have prickly seeds; others say that it is called in various languages by names equivalent to Hispanica, Spanish. Spinach was not known to the ancients, and it was a novelty in Europe in the 16th century. It is probably a native of western Asia. The plant is cultivated both as an annual and a biennial; it has petioled, ovate or triangular, succulent leaves; the flower stalks are 2 to 3 ft. high, hollow, furrowed, and branching; the apetalous flowers are dioecious, the male in long spikes, the female in clusters at every joint of the stem; the calyx in the pistillate flowers hardens and forms an involucre to the seeds, and in some varieties has two or three horns on the sides. But few varieties are known, the principal being the prickly, the smooth-seeded, and the lettuce-leaved.