Prota 2: Vegetables/Légumes
Chenopodiaceae (APG: Amaranthaceae)
2n = 12
Spinach (En). Epinard (Fr). Espinafre (Po).
Origin and geographic distribution
Spinach is not known in a wild state. It probably originated in northern Iran, Afghanistan and Turkmenistan where related wild species such as Spinacia tetrandra Steven ex M.Bieb. and Spinacea turkestanica Iljin can be found. It spread to China in the 7th century and to Europe in the 12th century. Spinach is now cultivated worldwide, mostly in temperate regions, but also in the cooler parts of the tropics. In tropical Africa it is grown to a limited extent in the highland areas of East and southern Africa.
Spinach is an important green leafy vegetable in temperate climates. The entire above -ground part of young plants or the tops of older plants are generally consumed after light cooking. Raw spinach is sometimes eaten in salads. In Africa it is entirely a fresh market product; in western Europe and North America more than half of the produce is processed into canned or deep-frozen products.
Production and international trade
In 2002 some 2.5 million t fresh spinach was produced worldwide from 170,000 ha, excluding China. The total area under spinach was 30,000 ha in Europe, 26,000 ha in Japan, 22,000 ha in Turkey and 18,000 ha in North America. The area for China alone was estimated at 590,000 ha with a production of 7.8 million t, but this probably includes several other green leafy vegetables. No statistics are available for tropical Africa, because here spinach is only grown as a home garden crop for European cuisine.
Spinach contains per 100 g of fresh leaves (ribs and stems removed, 81% of the product as purchased): water 89.7 g, energy 105 kJ (25 kcal), protein 2.8 g, fat 0.8 g, carbohydrate 1.6 g, dietary fibre 2.1 g, Ca 170 mg, Mg 54 mg, P 45 mg, Fe 2.1 mg, Zn 0.7 mg, carotene 3535 μg, thiamin 0.07 mg, riboflavin 0.09 mg, niacin 1.2 mg, folate 150 μg, ascorbic acid 26 mg (Holland, B., Unwin, I.D. & Buss, D.H., 1991). In addition to a high nutritional value with respect to micronutrients, spinach is a good source of flavonoid antioxidants. It also contains oxalic acid and free nitrates, but these are not considered harmful when average consumption is less than 100 g spinach per day.
Adulterations and substitutes
In Africa Ceylon spinach (Basella alba L.) is a reasonable substitute for spinach. There is also a wide variety of other leafy vegetables such as amaranths and Solanum species.
Usually dioecious, glabrous annual herb up to 150 cm tall, with a long taproot. Leaves initially forming a rosette, arranged spirally on stems, simple; stipules absent; petiole 6–12 cm long; blade angular-ovate to hastate, with round to sharply pointed basal lobes, 9–30 cm × 7–20 cm, entire, pale to dark green. Inflorescence an axillary cluster, in male plants elongated and spike-like, up to 10 cm long. Flowers usually unisexual, rarely bisexual, small, greenish; male flowers with (2–)4(–5)-lobed perianth and 3–5 stamens; female flowers without perianth but with 2(–4) bracteoles becoming a hard shell tightly enveloping the fruit, ovary superior, 1 -celled, stigmas 4–5(–6), thread-like. Fruit a utricle, indehiscent, teeth of envelope sometimes developing into prickles, 1-seeded. Seed dull, obtusely margined. Seedling with epigeal germination.
Other botanical information
Many cultivar classifications exist, based on fruit and leaf characteristics. A major division is into cultivars with prickly fruits, also classified as var. oleracea, and cultivars with non-prickly, round fruits, also classified as var. inermis (Moench) Metzg. or var. glabra (Mill.) Moench. Cultivars are also grouped according to leaf colour (pale or dark green) and leaf texture (smooth, semi-smooth and crumpled). Asian-type spinach cultivars are fast-growing and quick-bolting, have hastate, thin and smooth leaves, long petioles which are purple-red at the base, and often prickly fruits. Leaves should be dark green according to Japanese and pale green to Chinese preferences. European and American cultivars vary from quick-growing winter/spring types with pale green, thin and smooth leaves to slow-bolting summer types with dark green, smooth to crumpled leaves; the petiole is green or pink at the base.
Examples of old open-pollinated cultivars are ‘Munsterlander’ (smooth leaves) and ‘Bloomsdale Longstanding’ (crumpled leaves). All modern cultivars are F1 hybrids.
Growth and development
Spinach is normally dioecious with almost equal proportions of male and female plants, but many gradations of monoecism and hermaphroditism are known. In horticulture, the fruit of spinach (utricle) is usually called the seed. Dry spinach seed will remain viable for 2–3 years at ambient temperatures and 5–6 years when stored at 5ºC and 30% relative humidity. Depending on season and genotype, seedlings emerge 6–20 days after sowing and 35–100 days later the rosette is fully grown with the first signs of the flowering stem. Spinach is wind-pollinated. Seeds are mature about 60–70 days after flowering, when plants quickly senesce and die off.
Asian spinach cultivars, being adapted to short-day autumn or winter seasons, bolt readily in response to photoperiods of 12–14 hours. In Europe spinach is grown mostly in early spring and summer (north-western Europe) and requires a daylength of at least 14 hours for stem and flower formation. Optimum growing temperatures are 15–20ºC, but spinach is tolerant of low temperatures (3ºC) and even of light frost in some winter types. Vegetative growth is retarded by temperatures in excess of 27ºC. In East Africa spinach cannot be grown successfully at altitudes below 1200 m. Soils should be light in texture, fertile, well-drained, rich in organic matter and with pH 6–7.5.
Control of weeds can only be carried out shortly before sowing by tillage or application of herbicides. For optimum yield and quality spinach needs high doses of N and K fertilizers as well as a regular water supply throughout the season.
Propagation and planting
The weight of 1000 seeds is 9–13 g. Spinach seeds are broadcast, or preferably sown in rows (5–15 cm apart) 1–3 cm deep in carefully prepared soil. Seed rates are 15–25 kg/ha for Asian-type spinach, 60–100 kg/ha for the European and American processing (deep-freezing and canning) industry, 150 kg/ha (summer) to 400 kg/ha (winter/spring) for the fresh market.
Diseases and pests
The most important disease is downy mildew (Peronospora farinosa f.sp. spinaciae). Control by fungicides is difficult. Host resistance to 7 physiological races is available in some modern F1 hybrids, but a new virulent race has been found recently that is capable of overcoming this resistance. Blight, caused by cucumber mosaic virus (CMV), is especially important in warm and humid conditions; chemical control of the vector aphids (Aphis fabae and Myzus persicae) reduces incidence and some cultivars are blight tolerant. Fusarium decline (Fusarium oxysporum f.sp. spinaciae) and white rust (Albugo occidentalis) are particularly important in the United States. Seedling damping-off caused by Pythium spp. and Rhizoctonia spp. can be prevented by seed-dressing with fungicides. Bacterial rot (Erwinia carotovora) may destroy harvested spinach leaves when stored in moist and warm conditions. Pests include aphids, leaf miner (Liriomyza spp.) and nematodes (Heterodera spp. and Ditylenchus dipsaci).
In Asia whole plants with 8–10 leaves are harvested, the roots are cut 1 cm below the plant base and the product is sold in bundles of 10–15 plants. In Europe and North America spinach for the fresh market is harvested by mowing the crop just above ground level at a young stage and spinach for the processing industry at the first sign of flowering stem formation.
Yields vary from 10 t/ha of fresh leaves in Asia to 35 t/ha for summer crops in Europe and the United States. Seed yields are 1.5–2.0 t/ha.
Handling after harvest
A spinach crop has to reach the market very soon after harvesting to be consumed as a fresh product within 2–3 days, or within 24 hours for canning or deep-freezing, to avoid loss of quality and nutritional value.
Working collections and germplasm of Spinacia spp. are present in some research centres in Europe (CGN-PGR, Wageningen, Netherlands), the United States, Japan and the Russian Federation. Recent molecular characterization has indicated that the genetic variation in these germplasm collections is not large.
Present breeding programmes aim at F1 hybrid cultivars between highly female monoecious and highly male monoecious inbred lines. Sex expression is controlled by an X/Y heterosomal system and two strongly linked autosomal genes. The main breeding objectives depend on season, climate and preferred type: fast growth, slow bolting, high yields, round seed, leaf colour (pale or dark green) and type (smooth or crumpled), erect leaves, better heat tolerance and resistance to downy mildew, cucumber mosaic virus and other diseases.
Spinach will continue to be a very important, high-yielding and nutritious leafy vegetable in temperate climates of Europe, North America and eastern Asia. In tropical Africa it will remain only suitable for cultivation in the highlands.
• Correll, J.C., Irish, B.M., Koike, S.T., Schafer, J. & Morelock, T.E., 2003. Update on downy mildew and white rust on spinach in the United States. In: Van Hintum, T.J.L., Lebeda, A., Pink, D. & Schut, J. (Editors). Proceedings of the Eucarpia Meeting on Leafy Vegetables Genetics and Breeding, Noordwijkerhout, Netherlands, 19–21 March 2003. Centre for Genetic Resources, Wageningen, Netherlands. pp. 49–54.
• Correll, J.C., Morelock, T.E., Black, M.C., Koike, S.T., Brandenberger, L.P. & Daniello, F.J., 1994. Economically important diseases of spinach. Plant Disease 78: 653–660.
• Parlevliet, J.E., 1968. Breeding for earliness in spinach (Spinacia oleracea L.) as based on environmental and genetic factors. Euphytica 17: 21–27.
• Rubatzky, V.E. & Yamaguchi, M., 1997. World vegetables: principles, production and nutritive values. 2nd Edition. Chapman & Hall, New York, United States. 843 pp.
• Shinohara, S. (Editor), 1984. Vegetable seed production technology of Japan. Vol. 1. Shinohara's Authorized Agricultural Consulting Engineer Office, Tokyo, Japan. 432 pp.
• Sneep, J., 1982. The domestication of spinach and the breeding history of its varieties. Euphytica 1982, Supplement 2. 27 pp.
• van der Vossen, H.A.M., 1993. Spinacia oleracea L. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 266–268.
• Williamson, J., 1955. Useful plants of Nyasaland. The Government Printer, Zomba, Nyasaland. 168 pp. (Reprint: Williamson, J., 1975. Useful plants of Malawi. University of Malawi, Zomba, Malawi).
• Bose, T.K. & Som, M.G. (Editors), 1986. Vegetable crops in India. Naya Prokash Press, Calcutta, India. pp. 655–669.
• De Kraker, J. (Editor), 1991. Teelt van Spinazie. PAGV Teelthandleiding No. 38, Lelystad, Netherlands. 64 pp.
• Holland, B., Unwin, I.D. & Buss, D.H., 1991. Vegetables, herbs and spices. The fifth supplement to McCance & Widdowson’s The Composition of Foods. 4th Edition. Royal Society of Chemistry, Cambridge, United Kingdom. 163 pp.
• Irish, B.M., Correll, J.C., de los Reyes, B. & Morlock, T.E., 2003. Molecular characterization of spinach. Proceedings of the National Spinach Conference, November 20–21, 2003, Lafayetteville AR, United States. p. 16.
• Prior, R.L., 2003. Spinach as a source of antioxidant phytochemicals with potential health effects. Proceedings of the National Spinach Conference, November 20–21, 2003, Lafayetteville AR, United States. pp. 3–4.
Sources of illustration
• Hess, H.E., Landolt, E. & Hirzel, R., 1967. Flora der Schweiz und angrenzender Gebiete. Band I: Pteridophyta bis Caryophyllaceae. Birkhäuser Verlag, Basel, Switzerland. 858 pp.
• Mansfeld, R., 1986. Verzeichnis landwirtschaftlicher und gärtnerischer Kulturpflanzen (ohne Zierpflanzen). 2nd edition, revised by J. Schultze-Motel. 4 volumes. Springer Verlag, Berlin, Germany. 1998 pp.
• Vaughan, J.G. & Geissler, C.A., 1997. The new Oxford book of food plants. Oxford University Press, Oxford, New York, Tokyo. 239 pp.
Correct citation of this article:
van der Vossen, H.A.M., 2004. Spinacia oleracea L. In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.
1, habit; 2, stem with male inflorescences; 3, part of stem with prickly fruits; 4, part of stem with non-prickly fruits.
bunches of leaves on the market
top view of plant
plants grown from prickly fruits (left) and from non-prickly fruits