Everything you need to know about spinach cultivation, production and growth. Learn about:- 1. Introduction to Spinach 2. Origin and Distribution of Spinach 3. Composition and Uses 4. Climate and Soil Required for Cultivation 5. Sowing Time 6. Manurial Requirement for Cultivation 7. Irrigation Requirement for Cultivation 8. Intercultural Operations 9. Harvesting and Yielding 10. Packing and Storing 11. Cultivated Varieties.
Contents:
- Introduction to Spinach
- Origin and Distribution of Spinach
- Composition and Uses of Spinach
- Climate and Soil Required for Cultivating Spinach
- Sowing Time of Spinach
- Manurial Requirement for Spinach Cultivation
- Irrigation Requirement for Spinach Cultivation
- Intercultural Operations of Spinach
- Harvesting and Yielding of Spinach
- Packing and Storing of Spinach
- Cultivated Varieties of Spinach
1. Introduction
to Spinach:
Spinach belongs to the genus Spinacia and species oleracea. In Latin, spinach means spiny fruit and oleracea means herbaceous garden herb. The word spinach is derived from a Spanish word Hispania. The close relatives of Spinacia oleracea are Spinacia tetrandra and Spinacia turkistanica.
Spinach is though the most important potherb, its cultivation is restricted to smaller areas in the hills and parts of north as well as south India. It is a popular vegetable in the USA, Canada, and Europe. Italy, France, Germany, Netherlands, and United States are the leading countries where it is grown on a commercial scale for shipment to distant markets and for canning and freezing.
Spinach is an annual herbaceous plant for leaf production and biennial for seed production and grown in temperate regions exclusively for its leaves. The root system consisting of many fibrous developing from a slightly thickened taproot is relatively thick and shallow. Like beet leaf, it produces rosette leaves from a much-shortened stem near the ground surface during, the vegetative stage. Later on, the stem elongates and forms flower stalks during reproductive phase.
The shape of its leaves is quite different from that of beet leaf. Leaves vary in shape and thickness; their margins may be smooth or wavy and surfaces smooth and semi to heavily savoyed. Leaf color varies from light green to dark red. Its thin petioles are habitually as long as the leaf blades and often become hollow when the leaves are fully expanded. Flowers that vary from 6 to 12 per cluster are small greenish axillary and borne in clusters on both large stems and small branches.
Flowers may be staminate, pistillate, or hermaphrodite and remain receptive for a week or longer. The fertilized ovary after pollination taking place mostly by wind develops into a one-seeded fruit (utricle), however, in spinach often parthenocarpic fruits occur. Seed may have either a smooth round or an irregularly prickly shape. Seeds in their outer layer contain inhibitor.
Spinach is usually classified as a dioecious plant though it is not exactly true since in spinach field varying sexual types occur. The plant types are male, female, or both male and female, however, the degree of plant to be monoecious is influenced by either genetics and/or environment. Infrequently, hermaphrodite flowers appear.
Based on flowering or sex expression characteristics described four types of plants given as under:
1. Extreme Males:
Such plants are short in stature (smaller) with minimal foliage, flower earlier than other type of plants, and die after flowering. They produce only staminate (male) flowers, which are essential to supply pollens for the pollination of female flowers but do not produce seeds.
2. Vegetative Males:
Such plants are giant type (tall and larger) with more foliage and flower slightly later than extreme males. They bear only staminate (male) flowers, and thus, do not produce seeds.
3. Monoecious Plants:
Such plants have well-developed foliage and are slow in flowering. They bear both staminate (male) and pistillate (female) flowers on the same plant but separately on different positions and able to produce seeds.
4. Female Plants:
Such plants have well-developed foliage and are very late in flowering. They bear only pistillate (female) flowers and produce seeds, provided, they are grown with few rows of male plants, which supply pollens for the pollination of female flowers.
Though the male plants are inherently having short stature (smaller) with minimal foliage it is very tricky to ascertain the predominating sex expression of spinach plants prior to flowering. From economic point of view, female and vegetative male plants are preferred since they have well-developed (larger) foliage and high yielding capacity and are slow in bolting.
2. Origin and Distribution
of Spinach:
Southwest Asia is thought to be the origin of spinach, which was first time cultivated by the Arabs and taken to Spain by Moors from where it spread to other parts of the world, however, a group inhabitant considers its origin near Iran where it has been cultivated for at least 2000 years.
The crop was known in China as early as the 7th century A.D. and grown in Persia about 2000 years ago, and its cultivation in North Africa and Europe began about 1000 A.D. It was introduced in North America by Arabs. The prickly seeded spinach was used in Europe in 1351, whereas, smooth seeded was known in 1552.
3. Composition and Uses of Spinach:
Composition:
Spinach is rich in vitamins particularly carotene, a precursor of vitamin A, and minerals like iron and calcium, however, calcium is said to be most likely unavailable as it occurs united with oxalic acid to form calcium oxalate, which is responsible for the formation of stone in kidney or urinary system. Spinach contains appreciable quantities of ascorbic acid and riboflavin and small quantity of thiamine.
Ascorbic acid content increases with the plant age. Phylloquinone (vitamin K1) at a level of 299.5 µg/100 g is reported for spinach, and its level increases with plant maturity. The content of phylloquinone in spinach varies with geographical location due to differences in soil, climate, and other growth conditions. Histamine is also found available in its leaves. The nutritional values and chemical composition per 100 g edible portion of spinach are given in Table 23.1.
Spinach calcium is found to be less soluble than that from skim milk, and deprived availability of calcium from spinach has been corroborated in humans and rats too. Even cooking spinach in water for 20 minutes had no effect on the availability of calcium. Similarly, only about 2.8% of the total iron is available in vitro.
Uses:
Like beet leaf, spinach is also liked by the people. It is widely used uncooked in salads. The leaves are cooked as vegetable either alone or mixed with other vegetables and can be used raw in salads. Spinach leaves and tender petioles are cooked, steamed, or boiled for the preparation of dishes like pastries, souffles, and soups. Sometimes spinach and Swiss chard are cooked combined to give a blend of their pleasant flavor. The crop is also processed by both freezing and canning.
The significance of dark green leafy vegetables in human nutrition is world over well recognized, however, throughout the world their consumption appears to be underutilized and in some areas even diminishing completely. The inclusion of dark green leafy vegetables that are innately rich in β-carotene (pro-vitamin A) is strongly recommended by the nutritionists and dieticians to cure the vitamin A deficiencies.
Being rich in fibers spinach supplies roughage essentially required in the daily diet for normal movement of bowel. Its consumption prevents constipation, which causes colorectal cancer. A daily dose of spinach extract prevents some loss of long-term memory and learning ability and spinach is the most potent in protecting different types of nerve cells in various parts of brain against the effect of aging.
With the age, the body cells become sluggish in responding to chemicals stimulation but spinach has been scored best among the fortified diets in a test of nerve cells in the cerebellum, a part of the brain that maintains balance and coordination. Spinach because of having specific phytonutrients is considered more effective than the strawberries.
Spinach contains many anti-nutritional components like oxalic acid and nitrate in abundance. In some individuals who are tend to stone formation its frequent consumption in large quantities is very deleterious and causes serious health hazards especially to infants. Spinach contains oxalic acid, which in combination with calcium forms insoluble calcium oxalate reducing dietary iron and magnesium availability.
Protein in spinach has been revealed to have hypocholesterolemic properties. Excessive accumulation of nitrate in spinach has been found to be associated with a disease methemoglobinemia in humans. In spinach, excessive nitrate reduced to nitrite either in saliva during chewing or in the upper gastrointestinal tract not only causes methemoglobinemia in infants but also amplifies the jeopardy of formation of carcinogenic nitrosamines.
The plants those accumulate higher nitrates are also known to contain sizeable amounts of nitrite. Post-harvest storage of such vegetables also leads to accumulation of nitrite due to reduction of nitrate through either enzymes present in plants or activities of microbes, however, exposure of spinach plants to light before harvesting decreases the nitrate levels, thus, harvesting should be done in the afternoon, since low light and low temperature favor the accumulation of nitrate.
Conversely, storage of spinach leaves at 8° and 22°C for 24 h is reported to increase the nitrate by 54 and 27%, respectively, therefore, it is suggested that spinach should be stored for minimum time. High nitrate content may also be due to processing problems like can corrosion. Variations in nitrate levels of spinach tissues may be due to cultivar, application of higher doses of nitrogenous fertilizers, atmospheric temperatures, or activity of nitrate- reductase enzyme in leaf blades, hence, developing cultivars those accumulate fewer nitrates would be rather advantageous to the consumers.
The content of oxalate in tissues of spinach intensifies with growth, light intensity, and an increase in atmospheric temperature, though it is influenced rather fewer by the type of fertilizer used during cultivation. Synthesis of oxalic acid is greater at lower rather at higher temperature. It is assumed that L-ascorbic acid present in oxalate-accumulating plants including spinach might be metabolized into oxalic acid. Glycolate is also supposed to be an efficient precursor of oxalic acid in spinach leaves.
4. Climate and Soil Required for Cultivating Spinach
:
Spinach is a purely cool season crop, thus, grows best in moist seasons at an average temperature range of 16° to 18°C. Though the germination of seeds is better at lower (5-10°C) than at higher (25°C) temperature, emergence is slower at low temperature. Seeds may germinate even at 0°C but emergence is tremendously slow. The optimum temperature for spinach seed germination is 20°C and for growth 18-20°C, however, the growth is slow at 10°C.
Low temperature tends to increase leaf thickness but decreases leaf size and smoothness. Thermo-quiescence stage usually occurs above 30°C temperature. The spinach plants can withstand freezing frost better than other winter vegetable crop plants, and after acclimatization can tolerate freezing temperature as low as -10°C. The tolerance in spinach to freezing temperature is attributed to the presence of cold- regulated proteins in its leaves.
An increase in light intensity and atmospheric temperature increases the production of biomass and the contents of carotene and ascorbic acid since environmental conditions influence leaf number and size. Hu et al. (2004) found significant differences in height and leaf area (p < 0.01) of spinach grown in night-cooling greenhouse and control. It produces higher yield under short day and mild temperature, hence, it is more popular in the hills under temperate climatic conditions.
Since it is a long-day plant for flowering, under long day and warm weather conditions spinach has the tendency to form seed stalk, therefore, it is not possible to grow spinach during spring season in plains, especially when the days are long. The spinach for processing purposes is normally grown under a condition of short days so that more than one harvest can be made before the plants start bolting.
The critical photoperiod to develop seed stalk ranges between 12.5 and 15 h. Although photoperiod is the key stimulus to induce flowering but high temperature exposure after flower initiation causes rapid stem elongation, which almost inhibits vegetative growth, and as a result, the new leaves formed are small, narrow, and pointed. Hu et al. (2004) suggested that higher quality of spinach could be obtained from night-cooling greenhouse in summer.
Spinach can be grown on any good soil provided it is having proper drainage system but sandy loam soils rich in organic matter are far better than heavier soils. Spinach performs better on soils with high moisture holding capacity. Plant is tolerant to salinity but sensitive to acid soils since high acidity causes serious injury to this crop.
It can be grown successfully on soils having a pH range of 6.0 to 7.0. The most optimum soil pH is 6.0-6.8 for its cultivation however, it can be grown at a pH up to 10.5. If the soil pH is less than 5.5 liming is essentially required. Proper land preparation and adequate soil moisture are must to ensure satisfactory seed germination and for further growth of seedlings.
5.
Sowing Time of Spinach:
Sowing time of spinach varies from region to region as given below:
According to Thakur (2001), the sowing time of spinach at lower hills is July-November and February-March and at high hills March-April. The crop sown in spring-summer usually has a greater tendency to bolt. In northern Europe, spinach is grown in glasshouses at a limited scale during winter and early spring when outdoor cultivation is not possible due to adverse temperature conditions.
Sowing rates generally vary with the method of sowing and the intended use of crop. Spinach requires relatively higher seed rate than beet leaf since due to its dioecious nature about 50% of the plants may be the male with poor growth, which affects the yield. It is impossible to recognize and remove the male plants unless the vegetative phase of plants converts to reproductive phase, thus, about 37-45 kg seed is required to sow a hectare land area.
Like beet leaf, spinach is also propagated by seeds but Yeoung et al. (2004) obtained high economic efficiency in terms of growth rate, yield, and quality with transplanting compared to direct sowing. The method of sowing is almost similar to beet leaf crop, however, spacing between spinach plants influences the number of leaves and their size, and high plant population density contributes to early bolting.
The plant population density for fresh market production averages about 60 plants per square meter, whereas, plant density is doubled when the crop is raised for processing purpose. Lower plant population density facilitates hand harvesting for bunching of leaves or intact plants.
On the other hand, high plant population density results in more upright leaf growth, which is desirable for mechanical harvesting. Zarate and Vieira (2004) obtained higher fresh mass yield of spinach from mono cropping than intercropping, however, the land equivalent ratio in terms of mass yield of cultures (1.55) was higher under intercropping with bunching onion than mono-cropping system.
The seeds are sown either by broadcasting or in shallow furrows. However, sowing seeds in lines is better over broadcasting method as it facilitates cultural operations and harvesting of crop. Depending on soil type and moisture availability, the seeds are sown at a depth of 3-4 cm in lines 10 cm apart.
However, sowing seeds at a row-to-row spacing of 20-22 cm encourages optimum plant growth. The crop can be raised in either narrow raised bands or flat beds depending on drainage facilities. Soaking seeds before sowing in tap water or commercial acid can improve germination since soaking in water or acid removes water-soluble inhibitors and softens the pericarp.
6. Manurial Requirement
for Spinach Cultivation:
The requirement of nutrients is more or less the same as those for the beet leaf crop. Application of nitrogenous fertilizers normally increases the leaf production of spinach grown in winters since the loss of nitrogen through nitrification is less due to low soil temperature in winters.
Spinach is fertilized well to meet the requirement of plants for their fast growth that arises in a short period since lack of nitrogen resulted in yellow leaves, while lack of phosphorous and potash resulted in dry leaf tops and leaf necrosis, respectively.
About two-third of the total crop biomass is produced by the crop during the last third of the growth duration so to meet out the nutrients demand of quick growing crop plants appropriate scheduling of fertilizers application is essential. Thakur (2001) recommended the farmyard manure 10 t/ha, nitrogen 75 kg, phosphorus 60 kg and potash 30 kg/ha, while Singh and Joshi (1960) recommended 25 cartloads of farmyard manure as a basal dose followed by 3 top dressings each of 112-115 kg/ ha of ammonium sulfate.
Based on findings of various researchers, Kale and Kale (1984) recommended farmyard manure 25 cartloads, nitrogen 50-190 kg, and phosphorus and potassium each of 88 kg/ha, however, the tangible doses of farmyard manure and different fertilizers to be supplied to the crop should be based on physico-chemical analysis of soil.
The crop requires more nitrogen, which increases the fresh green leaves yield and total crop dry matter. Li et al. (2004) recommended to supply the spinach crop with a total nitrogen of 164 and 224 kg/ha for sprinkler irrigation and strip irrigation, respectively under similar conditions.
Mitova and Stancheva (2003) reported that nitrogen rates from 100 to 500 mg/kg soil given in mineral form showed a depressive effect on fresh and dry biomass of spinach as a second crop while the same quantities applied in organic form have a simulative effect on the plant growth and development.
The average leaf yield and N content of leaf increased with increasing rates of nitrogen, however, the leaf Fe, and Mn contents decreased. Yield reductions of 80% were obtained after insufficient P supply or NPK supply, while insufficient B or Cu resulted in 63-64% yield losses. Surpluses of N, Na, and CI, as well as insufficient K, resulted in 31-48% yield losses. The quality of spinach is also influenced by the application of fertilizers. Nitrogen application increased protein, beta-carotene, reducing sugars, and ascorbic acid.
However, Mitova and Stancheva, (2003) found no influence of increased equivalent nitrogen quantities applied in organic (farmyard manure) and mineral form (ammonium nitrate) on yield and quality of spinach.
Singh et al., (1972) reported that foliar application of s-triazines increased the protein, iron, magnesium, phosphorus, and potassium contents in leaves of spinach. Application of nitrogenous fertilizer has a positive effect on vitamin B1 and B2 contents but nitrogenous and potash fertilizers have a negative effect on content of vitamin E.
Farmyard manure should be applied at the time of land preparation and mixed thoroughly into the soil by repeated ploughings. Full dose of phosphorus and potassium and one-third dose of nitrogen should be applied before sowing at the time of last ploughing, and rest of the two- third dose of nitrogen should be given in standing crop in two equal splits after first and second cuttings. Besides, foliar spray of urea 1.5% may be done 15 days after germination and repeated after every cutting to fasten the growth rate.
7. Irrigation Requirement
for Spinach Cultivation:
The irrigation requirement of spinach crop is usually not too high because of less loss of water from the plants through a process of low transpiration since its cultivation is done in cool season, thus, on an average 250 mm of irrigation water is normally enough for this crop. Yet, the plants can easily be stressed from inadequate moisture due to its shallow root system. Water logging conditions are also detrimental to the crop.
The first light irrigation is given just after sowing if soil moisture in the field at the time of sowing is not sufficient, and subsequent irrigations are given as per the requirement of the crop. In general, irrigation is applied at an interval of 4-6 days in summer and 10-12 days in winter for providing soil moisture adequate for optimum growth of plants. The spinach plants grow markedly better in the sprinkler irrigation treatment than in the strip irrigation pattern.
8. Intercultural Operations
of Spinach:
All intercultural operations are done similarly to beet leaf. Keep the field weed free is very essential especially for the crop grown for processing since weeds especially that are similar in appearance to spinach and difficult to separate are contaminants in crop, therefore, removal of such weeds are the most indispensable. Regular hoeing after each cutting and use of effective weedicides can keep the weed population low.
The crop grown for fresh market is hardly ever thinned since the operation is too labor expensive, hence, to obtain optimal plant population density the seed rate is ascertained according to germination percentage, seed vigor, seed size, and field conditions. Higher yield of spinach can be obtained by growing high-performance hybrids having high degree of femaleness.
9. Harvesting
and Yielding of Spinach:
Spinach crop becomes ready for harvest when the plants attain 5-6 leaves, which is attained 40- 50 days after sowing depending on temperature and other climatic components, and harvesting continues over-winter until just before the seed stalk develops. Higher yield from spinach crop can be obtained when cutting is done when the leaves have developed to full size, marketable size. Delaying in harvesting increases the leaves weight, however, leaf quality may be affected adversely.
For fresh market, it is harvested by cutting the plant at the soil surface just below the lowest leaves. However, for processing purposes, harvesting is done by cutting the plants about 2-3 cm above the soil surface. Harvesting is usually done by using a sharp knife to avoid maceration of tissues at cut end. In advanced countries for the fresh market, spinach is harvested mechanically, and the leaves are gathered and bulk handled rather than bunched.
Separate machines have been manufactured to cut the whole plants for fresh market and to cut only leaves for processing, though, Clip-topped spinach is preferred more than the crown-cut produce since the yield of Clip- topped spinach is more and labor required for packaging is less.
The harvesting machine is so adjusted that it may cut the plants 10-15 cm above the growing point to reduce the undesirable portion of petioles and also to allow the plants to re- growth for a possible second harvest 3-4 weeks later since a high leaf blade to petiole ratio, which increases the value of the processed product is preferred more by the processing industries.
It is advisable not to harvest the crop immediately after rain or heavy dew because the leaves are very turgid and break easily when wet, however, a slight wilting may prevent this breaking so to minimize leaf damage, spinach is harvested later in the day when the leaves are less turgid.
All yellow, injured, and diseased leaves are trimmed-off during preparation of produce for the market, and the produce is handled carefully to prevent bruising or breaking of leaves and stem. Only the intact plants are trimmed off, not all hand-cut leaves. Washing of produce should generally be avoided since washing usually results in injury.
Ryall and Lipton (1972) suggested that spinach should be harvested only during the cooler parts of the day to minimize wilting, a major disorder of spinach, which is known to hasten the loss of ascorbic acid in spinach leaves but is of much less importance than unfavorable temperature. Spinach loses water more swiftly under a warm weather conditions than under cool conditions even at high relative humidity.
Spinach has a very high rate of respiration, hence, must be cooled rapidly to prevent weight loss and decay since overheating quickly destroys its quality. The temperature of produce may be lowered by vacuum cooling adopted by large operation or hydro cooling adopted by small operator.
Hydro cooling is very effective to maintain firmness of the leaves but it causes decaying of leaves, however, Ryall and Lipton (1972) reported that spinach could be package-iced, hydro cooled or vacuum-cooled equally well.
If hydro cooling is used, centrifuging about 3 minutes excess water is removed to retard decaying under higher temperature conditions. Hydro-vacuum cooling, where moisture is added during vacuum cooling, is useful in limiting wilting. Using chlorinated water (100 ppm) for washing or cooling the spinach prevents buildup of bacteria in water but has slight effect on its decaying.
A spinach plant in its growth duration about 25 leaves may produce, and on an average it gives a yield of fresh green biomass about 50-60 quintals per hectare in 3-4 cuttings. Processing crop yield ranges from 5, from single cut, to as much as 20 t/ha, from multiple cuts, however, fresh market yield of spinach is normally much less.
10. Packing
and Storing of Spinach:
Spinach is highly perishable due to its succulent large leaf surface area and high rate of respiration, thus, should be disposed-off immediately after harvesting. The several harvested intact plants before marketing are tied together in small bunches with twine/string for local market, however, for shipment, the harvested leaves after pre-cooling are packed in containers including the round bushel baskets, wire bound crates, or in hampers.
Crushed ice is placed on the top of the produce packed in the bushel baskets to keep the leaf tissues cool during shipment when refrigerator vehicles are used for distant transportation. As a rule, the quantity of ice placed in the container is about equal to the weight of the spinach.
For distant markets, it is packed in polythene bags. In retail stores, spinach is sold in prepackaged transparent polyethylene films bags, which allow exchange of metabolic gases and maintain high humidity by reducing evaporation.
Being highly perishable vegetable like beet leaf, it cannot be stored for long period. High temperature, low humidity, and rapid air movement often result in rapid wilting of green leafy vegetables, making the produce less attractive. Wilting is known to hasten the loss of ascorbic acid in spinach but is of much less importance than unfavorable temperature.
Spinach can be stored for 10 days at 0°C temperature and 95% relative humidity, however, Plantenius (1934) reported that spinach becomes unsuitable for sale after 24 days at 1.6°C, 7 days at 10°C, or 2-3½ days at 18.3°C. The controlled atmosphere (CA) prolongs the shelf life of spinach by about one week at 5°C. Murata and Veda (1967) found that CO2 enriched atmosphere (10% CO2) retarded yellowing of spinach and maintained the product in good quality for 3 weeks at 5°C.
Chlorophyll and ascorbic acid contents in spinach stored at 20°C for 6 days decreased greatly with the corresponding increase in yellowing, and by the 3rd day, ascorbic acid was lost about 83% at 20°C temperature. On the contrary, Watada et al., (1987) reported that thiamine increased sharply and riboflavin remained unaffected during storage.
They further reported that the degradation of chlorophyll by peroxidase enzyme in the presence of hydrogen peroxide was slower at 0°C than at 20°C but addition of L-ascorbic acid inhibited the degradation. While spinach was stored in a closed vessel at 29-32°C temperature and in refrigerator at 5°C for 2 days the vitamin A content decreased by 21.6 and 23.7%, respectively.
11. Cultivated Varieties
of Spinach:
In a breeding programme, resistance breeding and breeding for F1 hybrids are most important to improve the spinach crop since the F1 hybrid gives up to 20% higher yield than its parents give. The different sex types in spinach are related to F1 hybrid production by utilizing female lines in combination with known pollen (male) parent. Thompson (1955) suggested the use of monoecious plants for producing F1 hybrid seeds.
Monoecious plants on selfing segregate into females, monoecious, and male plants in varying proportion. Selection of high degree female plants (80-90%) and crossing them with the pollen parent results in F1 hybrid.
Spinach cultivars differ in seed and leaf morphology, thus, the cultivars can broadly be classified according to their seed and leaf morphology:
Based on the morphology of seed, the cultivars of spinach are categorized into two groups that are given as under:
(i) Prickly Seeded:
Similar to beet leaf, its seeds have the jagged/toothed surface than the smooth. Prickly seeded varieties perform better in hilly regions.
(ii) Round or Smooth Seeded:
Most commercial cultivars are smooth seeded, which makes them easier to sow and plant accurately. Round seeded varieties perform well in plain areas rather in hilly tracts.
According to leaf morphology, the spinach cultivars are classified into three groups that are given as under:
(i) Savoy (Wrinkled Leaf):
Lower temperature in night causes the leaves Savoy/wrinkled, which are preferred more for fresh marketing.
(ii) Semi-Savoy (Semi-Wrinkled Leaf):
The leaves are slightly Savoy/wrinkled. These are preferred for both fresh marketing and processing.
(iii) Smooth or Flat Leafed:
The leaves are flat and smooth surfaced and used for processing purpose.
The most popular spinach cultivars grown in India are Virginia Savoy, Early Smooth Leaf and a recently developed F1 hybrid SH-1, which are recommended by the Indian Agricultural Research Institute, New Delhi for cultivation under Indian conditions.
The characteristic features of some important improved varieties and F1 hybrids are described as under:
A Savoy-leaf type cultivar resistant to cucumber mosaic virus-1 developed through a cross between domestic Savoy type and an exotic introduction from Manchuria. It has smooth seeds, which are easy in threshing and grading. Its leaves are blistered large, thick, and dark green with round tips. The plants are upright, vigorous, and very early seeding. It is a late bolting cultivar suitable for sowing in September-October and gives 5-6 cuttings at 15-20 days interval.
A smooth round seeded cultivar produces small, light green, thin, and smooth leaves with a pointed apex.
A F1 hybrid developed at Indian Agricultural Research Institute, Regional Research Station, Katrain (Kullu Valley), Himachal Pradesh through a cross between Virginia Savoy and Japanese varieties. Its leaves are green semi-Savoy with blunt apex. This hybrid gives yield 20% higher than its parents give.
A broad-leaved late-bolting new spinach F1 hybrid from China is suitable for protected and open field cultivation. The indices of resistance to downy mildew (Peronospora farinosa) and virus are lower (by 28.8 and 25.1 %, respectively), and bolting occurs later by 15 days in Dongxin-1 than in the Japanese broad-leaved spinach.
i. Amsterdam Giant:
Plants of this variety are late seeding and have prickly seeds.
ii. Dark Green Bloomsdale:
This variety has the plants that are medium-early seeding.
iii. Hollandia:
This is a variety with no savoyed leaves in cool weather.
iv. Juliana:
The plants of this variety have blue-green leaves.
v. King of Denmark:
This variety also has the plants with blue-green leaves.
vi. Long Standing Bloomsdale:
The plants of this variety have dark green leaves.
vii. Nobel:
This variety can be distinguished by its medium green leaves.
viii. Old Domination:
This variety has medium-savoyed leaves.
ix. Vitro Flay:
The plants of this variety are with slightly savoyed leaves in cool weather.
The choice of a cultivar depends on its leaf characteristics, critical day length relative to the growing latitude and seasonal temperature since the cultivars of spinach are sensitive to both temperature and photoperiod. Usually, slow-bolting cultivars are preferred when planting is scheduled to get the crop mature during long days and warm temperature.
Earliness of a variety is associated with its growth rate since fast growing varieties are harvested earlier. Spinach growers prefer to grow varieties those are fast growing, slow-bolting, high yield, and suitable to the growing conditions. In glasshouse, only the cultivars those are having rapid foliage growth under a condition of short day and low temperature are used for cultivation.
For processing smooth or semi-Savoy cultivars are preferred more since they are fast growing, high yielding, and washed more easily, whereas, the leaf surfaces of Savoy cultivars may not easily be made soil particles free by washing. Cultivars with Savoy surface texture are ideal for fresh market since such leaves resist compression during packaging, and thus, allow better aeration, which helps in fast cooling and prolonging post-harvest life.