638 Spinacea oleraceaCommon Names: spinach Family: Chenopodiaceae (goosefoot Family)
Spinach is a fast growing, cool weather annual, cultivated for its dark green succulent leaves which grow in a basal rosette. There are two botanical varieties: Var. oleracea, the prickly-seeded spinaches, have seeds with spines and tend to be early maturing and more cold hardy. Var. inermis, the smooth or round-seeded types, have seeds lacking spines and tend to be slower to bolt in warm weather. The differences between the two have largely disappeared due to modern breeding, and both groups now include cultivars that are cold hardy and early maturing, and cultivars that are slower to bolt in warm weather; as well as cultivars that have smooth leaves and some with savoyed or crinkled leaves. Some of the modern spinach hybrids are resistant to downy mildew and spinach blight.
Spinacea oleracea Spinach originated in SW Asia and was first cultivated in Persia.
CultureSpinach can be grown for its leaves only during the cool months of the year. It quickly bolts to seed in warm weather or when the days begin to lengthen, even if it isn't warm. Day lengths of 13-15 hours will cause spinach to bolt. Crowded plants are likely to bolt even sooner. Spinach needs an abundant supply of nitrogen fertilizer. Light: Full sun or light shade unless you are trying to stretch the season into the warmer months, in which case spinach will appreciate mostly shade. Moisture: Never let spinach dry out. It needs well-drained soil, but plenty of watering. Mulch spinach plants as soon as they are large enough to work the mulch around them. Hardiness: USDA Zones 3 - 10. Spinach can take frosts and freezing temperatures down at least to 22ºF (-5.6ºC). It will bolt without producing significant leaves at temperatures above 75ºF (23.9ºC). In northern latitudes, fall-sown spinach often overwinters beneath the snow (especially if mulched) and starts growing again in very early spring. Propagation: Spinach is propagated by seeds. Plant some every 2-3 weeks to insure a continuous crop of young leaves. In USDA zones 3-6, plant the first crop 4-6 weeks before the expected last frost. In zones 7-8, plant in September, October or November. In zone 9, plant in December. If you're trying for a fall crop, sow thickly because spinach seeds germinate poorly in warm soil.
Individual outer leaves of spinach can be picked within 30 days after planting. The young leaves are best eaten raw in salads. As the season progresses and it looks like the spinach might start to bolt, harvest the entire plants by cutting the stems at ground level. The smooth-leaved varieties are easier to wash. Cook spinach just enough to wilt it and with only the water that clings to the leaves after rinsing. The iron in spinach is water soluble, so don't waste any water left in the pot after cooking. Frozen spinach (blanch in boiling water for 1-2 minutes before freezing) retains most of its nutritional value, flavor and color. Save the blanching water for soup stock. Try a little grated nutmeg on cooked spinach. Really.
Popeye the Sailor Man was right! Spinach is quite possibly the best of the highly nutritious leafy green vegetables. Spinach is high in vitamins A, C, and B2, calcium, iron, and anti-oxidant carotenoids. Numerous scientific studies have demonstrated that spinach, with its high levels of beta-carotene and other anti-oxidants, is a powerful cancer inhibitor. It also is believed that a diet high in spinach, which contains high levels of the carotenoids lutein and zeaxanthin, will help ward off age-related macular degeneration, the leading cause of irreversible blindness in older people.
Other members of the Chenopodiaceae that are nutritious and delicious potherbs are beets and Swiss chard (Beta vulgaris), orach (Atriplex hortensis) and quinoa (Chenopodium quinoa). Two heat-tolerant spinach substitutes are New Zealand spinach (Tetragonia tetragonioides, in the Tetragoniaceae), and Malabar spinach (Basella rubra, in the Basellaceae). Both are totally unrelated to spinach, but look a lot like it. Unfortunately, they don't taste as good as spinach.
Spinach contains oxalic acid, and excessive amounts can inhibit calcium absorption in some individuals.
Steve Christman 10/10/00; updated 12/14/00