Everything you need to know about strawberry cultivation, growth and harvest! Learn about: 1. Botany of Strawberry 2. Climate and Soil Required for Strawberry Cultivation 3. Orchard Cultural Practices 4. Propagation Techniques 5. Pollination and Protected Cultivation 6. Planting Operations 7. Flowering and Fruiting 8. Training 9. Harvesting and Handling.
Botany of Strawberry:
Fragaria x ananassa Duch. (Cultivated strawberry) is an octaploid (2n = 8x = 56) belongs to the family Rosaceae, sub-family Rosoideae. About 34 other species of Fragaria are found in Asia, North and South America and Europe. Wood strawberry (F. vesca) and Musky strawberry (F. moschata) were cultivated in Europe and Russia for centuries. Wood strawberries are small with both red and white coloured fruits.
Musky strawberries bear light red to purple coloured fruits. F. ananassa is a hybrid of two species F. chiloensis and F. virginiana. Strawberries are perennial, stoliniferous herbs which spread via stolons or runners. The leaves have three leaflets and arise from the crown. The plants of F. virginiana are tall bear imperfect flowers. The fruits are small sized, light to deep red in colour, flesh soft with pleasant aroma. The plants are fertile and both hermaphrodite and unisexual plants are produced.
It yields large quantity of runners. The plants of F. chiloensis are spreading in nature with stout stolon’s. The leaves are thick, blunt and toothed; flowers are white and borne in small cluster. The fruits are large sized. In this species, both hermaphrodite and unisexual male and female plants are found.
The strawberry is an aggregate fruit. The true fruits that contain the seeds of the strawberry are achenes. The achenes are the numerous, tiny, ellipsoid specks that cover the fruit surface. The edible portion of fruit is fleshy thalamus.
Climate and Soil Required for Strawberry Cultivation:
Strawberry grows best in temperate climate but can be grown with good success in subtropical climate. It always thrives well under selected agro-climatic conditions. A long growth period with growing warm summer and mild autumn is desirable. The plant growth observed maximum at 22°C day temperature and 7 – 13°C night temperature. Flower bud formation need daylight period of twelve hours or moderate temperature.
Strawberry prefers relatively low optimum temperature for growth and fruiting. The growth of the plants takes place better in short days and cool temperature. Being a short day plant, it requires exposure atleast for 10 days of about eight hour’s sunshine for initiation of flowering.
In winter, the plants remain dormant and thus help in breaking dormancy of the plant. In spring, due to rise in temperature the days become longer, the plants resume growth and initiate flowering. The commercial varieties of strawberry develop flower buds only during the short light period.
The strawberries are sensitive to frost damage and winter injury in temperate climate. The fruit yield is considerably reduced. The center of the open flower is damaged with frost, thus, causing symptoms of ‘Black Eye’. Occurrence of spring frost is also detrimental to strawberry plants. Flower open in sequence on the trusses and plant have long flowering period (April to early May), as such frost pockets should be avoided for its cultivation.
Long days and warm temperature favour leaf and runner production. Exposure of plants to long day after transplanting is proved beneficial in advancing flowers, extending flowering period, advance fruit maturity, reduce harvest span and improved fruit quality. High light intensity promotes ripening of berries. The high velocity of wind cause discolouration of leaves and may reduce the fruit yield.
Strawberries can be grown on wide variety of soil from sandy to loamy soils. However, it grows well in fertile, well drained soils, rich in organic matter with PH 5.5 – 6.5. Root formation is poor at high soil pH. On light soils, irrigation will be necessary to establish runners and maintain berry size and quality. Moisture should be adequate during dry season for obtaining high yields. The plants are sensitive to salinity and alkalinity conditions. Nematode infested soils should be avoided for strawberry cultivation. The soil erosion can be checked by growing cover crops. The soil rich in organic matter or light soils are considered better for runner formation.
Orchard Cultural Practices for Growing Strawberry:
i. Irrigation:
Regular watering to strawberry plants is very important for stable production over the years. It is a shallow-rooted plant that requires more frequent but less amount of water in each irrigation. Optimum irrigation improves size and general appearance of berries, enhance yield and extend harvesting period. Heavy watering leads to continuous growth of leaves and stolons and also enhances the incidence of Botrytis rot.
Early planting require more irrigation as runners are actively growing and will not withstand dry soil conditions. Late planting need lesser irrigations as they readily get established. The soil should always be just kept moist for good growth of the plant. During September – October, irrigation should be given twice a week. Irrigation interval should be kept weekly in November and fortnightly in December – January.
Irrigation is applied in furrows between the rows. Drip and sprinkler methods of irrigation are more suitable for strawberry plantation. Drip system should be run two or three times in a week and fertigation should be given fortnightly.
ii. Weed Control:
Weed poses serious threat in strawberry production. They compete with the strawberry plants for nutrients and moisture results low yield of poor quality fruits. Motha is one of most serious weed in strawberry. Mulching with black polythene effectively suppresses weed growth. Oxyfluorfen + napropamide @ 0.60 + 5.0 kg a.i/ha check weed population effectively in strawberry plantation in Jammu region.
Simazine 3 kg/ha in spring is reported to control the weeds effectively. Stomp 5 l/ha also reduce weed flora in strawberry fields.
iii. Mulching:
Mulching the strawberry field is very useful practice as it helps in conservation of soil moisture; checks weed growth and avoid the direct contact of berries with soil. Both organic and inorganic mulches are used in cultivation of strawberries. Mulches reduce the percentage of spoiled fruits and prevent the infection due to fruit root. Before mulching, the soil should be dusted with insecticide for protection against insects.
Strawberry beds can be mulched with pine needles, grain straw or saw dust. Black polythene mulch increase temperature of the soil and also soil moisture during summer. In arid-irrigated zone of Punjab at Abohar under micro-irrigation conditions, strawberry mulched with black polythene produced higher yield than mulched with clear polythene and paddy straw.
iv. Manuring and Fertilization:
The healthy and vigorous growth and optimum fruit yield of good quality can be achieved only with proper application of manures and fertilizers to strawberry plants. Excessive fertilization cause profuse vegetative growth, reduce yield, attract foliar diseases and winter injury to the plants.
In Himachal Pradesh, 50 tonnes of farmyard manure along with 40 kg P2O5 and 40 kg K2O per hectare is applied at the time of preparation of beds. Nitrogen @ 80 kg per hectare is applied in two split doses. Half the quantity is applied in the month of September or after the establishment of plants in September – October and half is given after blossoming. In another study, higher yield and better fruit quality was obtained with a fertilizer dose of 150 kg nitrogen and 75 kg, P2O5 per hectare.
In Kashmir, application of 50 – 70 tonnes of FYM along with 40 kg nitrogen and 80 kg K2O per hectare is given for adequate cropping.
In Uttarakhand hills, 25 – 50 tonnes of FYM, 75 – 100 kg nitrogen, 80 – 120 kg P2O5 and 50 – 80 kg K2O per hectare is applied. Half dose of nitrogen is given one month after planting and remaining half at the time of flowering. Whole phosphorus and half dose of potash is given at planting time. Remaining potash is applied at the time of flowering. Application of vermicompost to strawberry is very useful in improving plant growth and fruit yield. Vermicompost @ 10t/ha proved beneficial in increasing the yield and production of healthy fruits in Chandler variety.
Propagation Techniques for Strawberry:
Seed propagation in strawberry has little importance as the seedling do not come true- to-type. In vegetative method, strawberries are propagated by runners. Early formed runners are vigorous, have good root system and more productive. These runners should be preferred for planting. For nursery raising, sandy soils with irrigation facilities are preferred to produce quality runners. Heavy soils should be avoided for runner production. The soil should be rich in organic matter for better runner quality.
The freshly dug runners should be best planted in nursery bed during early winter or spring. The runners are detached from mother plants after attaining proper size. These are severed at the stolon and used as propagules. The runners used for propagation should always be healthy, vigorous and free from virus and diseases. A single plant of strawberry usually produces 12 to 18 runners. Runner production can be stimulated by using IBA @ 100 ppm or morphactin @ 50 ppm about 10 days before flowering.
The ideal time for planting for cold stored runners is the month of July. The runners in dormant stage are kept in cold store. Runners are lifted in December – January. Runners of ‘Pusa Early Dwarf’ variety store at 32°F in cold store for 60 days survive far better after transplanting than fresh materials.
Micro-Propagation:
Micro-propagation through tissue culture has emerged as the most widely used and viable techniques for large scale production of planting material. Strawberry plants are often produced through tissue culture to have virus free material. The plants from meristem culture produce higher yield than multiplied through runners.
Pollination and Protected Cultivation of Strawberry:
In strawberry, cross pollination by insects is useful since stigmas become receptive before the anthers release pollen. However, fertilization of achene is possible through self-pollination. Honey bees are the main pollinating agent but some more insects are also involved in pollination process. Apis mellifera (Italian Honey bees) play important role in pollination of strawberries and the fruit produced are better in size and develop better marketable quality.
The receptacle swells after fertilization, becomes fleshy and develops into a berry. Poor fruit setting is associated with external factors which might be responsible for reduction in stamen abortion. Pollen fertility is reduced due to low temperature and short days. Frost occurrence, hot dry winds, insect-pests and diseases attack at flowering leads to poor fruit setting in strawberries.
Nutrient status of soil also considered important in better flowering and fruit setting. Fruit-setting can be improved by spray application of plant growth regulators. GA3 @ 50 ppm sprayed four days after flowering and maleic hydrazine @ 0.1 – 0.3 per cent sprayed after flowering improve the yield by 30 – 40 per cent. The fruit size can be improved by spraying morphactin @ 50 ppm.
The commercial production of strawberry using the plasticulture system is becoming popular with the growers. Protected cultivation of strawberry in plastic tunnels, green houses and glass house structure is meant for early production of fruits. The plants under these structures flower one to one and half month earlier than the unprotected plants and produce ripe fruits earlier than those available from open cultivation. Plastic films of 150 mm can be used and kept for two years. Ventilation is provided to avoid excessive heat and to avoid development of malformed fruits.
Chandler variety is most suitable for growing in protected structures and produced best quality fruits. In plasticulture system, the raised beds are formed each year, fumigated and covered with plastic to prevent weed growth and erosion. Plants are planted through holes punched in this covering.
Use of plastic tunnels in Chandler cultivar enhanced earliness in fruit ripening and produced higher yield. Low tunnels of 50 cm height with transparent polythene film of 50 micron with the help of G1 wires can be installed in winter months from December to February to protect the plants from cold. Tunnels should be opened during day time for maintaining high temperature inside for early flowering and better fruit yield.
Planting Operations for Strawberry:
Preparation of Soil:
Before planting, the soil should be prepared well and removal of all the weeds is essential. Strawberry plants do not produce deep roots. However, the land should be properly prepared by deep ploughing before planting. While preparing land, soil should not be in wet condition and making a fine tilth for good structure is important.
There should be proper drainage for excess rain water. Application of desired quantity of manure and fertilizers be made and mixed well with the soil to make the nutrients easily available to the new runners. Roots of the newly planted strawberries need oxygen as well as soil moisture and warmth; therefore, soil should not be too compact or firm.
Planting should be done on well prepared raised beds, or flat beds, hill rows or matted rows during August-September. In hilly areas, transplanting is done in March-April and September-October. Staggered planting from mid-September to mid-October at bi-weekly/weekly interval can be made for longer period of availability of plants i.e. January to April.
In semi-arid region of Punjab, strawberry given micro-irrigation planted in mid-September enhanced plant growth and resulted early flowering (77 days) and fruiting (33 days). Under sub-tropical conditions of Jammu, planting of strawberry on 9 October coupled with black polythene mulching was considered most favourable in terms of fruit size and yield.
Late planting results in reduction in yield during the first year. The beds made for planting should be sufficiently large to accommodate the roots. The soil around the roots should be pressed properly for better anchorage. In Kashmir Valley, runners can be planted during October-November and upto February-March provided soil and weather conditions are favourable. Planting in Mahabaleshwar is done on raised beds of 4 x 3m or4 x 4m during November – December.
Systems of Planting:
The strawberry plants are planted according to different systems as follow:
(i) Single Hill Beds:
In this system, the plants are to be planted 30 cm apart within the rows. Row to row distance is kept 90 cms.
(ii) Mid-Hill Planting:
The distance from plant to plant and row to row is kept 30 x 60 cm under this system. Spacing of 30 x 30 cm is also commonly followed which accommodate population of 55000 plants per hectare.
(iii) Double-Row Beds:
In this system, the double row plants are grown on each bed with a distance of 30 X 30 cm within the row and plant to plant. Distance from one bed to another bed is kept 105 to 120 cms.
Planting of runners at 25 x 25 cm spacing with four rows of plants per bed accommodates one lakh plants per hectare. The planting distance can be kept from plant to plant 45 cm and row to row 60 – 75 cm. In Shalimar Kashmir Valley, double row system of planting is considered most suitable for strawberry crop and distance of 30 x 40 x 60 cm within plants, rows and between beds yield maximum benefit. In another study, spacing of 30 – 50 cm is rows 100 cm apart allowing the pickers to work conveniently between rows.
Flowering and Fruiting in Strawberry Plants:
The cultivated strawberry bear two types of flowers i.e.:
i. Hermaphrodite and
ii. Pistillate flowers.
The flowers occur in cluster and each flower contains five sepals and five petals. The inflorescence in strawberry is raceme type. A flower contains 60 to 600 pistils and 20 to 35 stamens. Plants bloom in late winter or early spring depending upon the location and climatic conditions.
The strawberry fruits follow simple sigmoid growth pattern. An exponential increase in fruit size in the later stages was related to fruit softening. Three distinct phases of fruit development takes place. The first phase begins after pollination and is associated with the development of nucleus in the carpel. It ends about 10 days after pollination. The second phase is dependent on an actively growing cellular endosperm.
The third phase starts after attainment of full size of embryo. This is termed as rapid enlargement of receptacle. This phase depend greatly on external application of growth substances. An increase in sugar content with corresponding decrease in acidity observed with the advancement of maturity.
Parthenocarpy:
Parthenocarpy in fruits of strawberry can be induced with exogenous application of auxin i.e. 1AA. It is reported that contribution of fertilized achene in promoting fruit growth can be replaced with growth regulators. In male sterile varieties, induction of parthenocarpy is more successful.
De-Blossoming:
In June bearing strawberries, flowers are removed during the first growing season. This practice promotes runner development as well as helps in better root system and results in good crop in the following year. In day-neutral and ever-bearing strawberries, flowers should be removed until end June. After that, flowers are allowed to continue for setting fruit for summer/fall harvest.
Training Systems Followed in Strawberry:
Three training systems are followed in strawberry i.e.:
i. Hill system,
ii. Spaced row system and
iii. Matted row system.
i. Hill System:
Multiple rows are made in groups of 2, 3 or 4 plants with 60 cm path between each group of rows. Plants are set 30 cm apart in multiple rows. Runners are removed so that the available nutrients may be utilized by the mother plant. This system is the best for growing day-neutral and overbearing varieties. The cost of production is more in hill system. The yield is less but fruits are larger in size.
ii. Spaced-Row System:
Runners are not removed. The number and spacing of new plant is regulated. The mother plants are set 30 to 75 cm apart in rows one meter apart. It helps in the increase of the size of the plant and fruit yield. Three to four plants may be allowed to develop from each runner.
iii. Matted-Row System:
This system is commonly followed in India and considered best for June bearing cultivars. The mother plant may be spaced 30 cm x 90 cm apart in rows 120 to 150 cm apart. Runners allowed to develop so that the plants occupy a space of 90 – 120 cm. The yield depends on the number of plants and spacing between plants and rows. Leaves can be moved off after harvest to eliminate diseased foliage and facilitate weed control and mulching.
Harvesting and Handling of Strawberry:
The strawberry plants starts fruiting after 3-4 months of planting. The fruit ripens from end February to April in the plains and during May and June at higher elevation like Kashmir, Nainital and Mahabaleshwar. Three successive crops can be taken but yield and quality deteriorate after two seasons.
The fruits are harvested along with the caps still attached and with their stalks when 50 percent of the surface has attained red colour. The fruits harvested at 75 per cent red colour, develop full red colour within 1-2 days at 21°C temperature. For sending to longer distant market, berries are harvested immediately after reaching full colour. For processing purpose, fruits are picked firm ripe with one to two third of the surface showing colour. For local markets, fruits are picked with cap and stem of about 12 mm length. Strawberries are allowed to ripen on the plant fully as they do not continue to ripen after harvest.
Strawberries do not mature uniformly, as such harvesting should be completed in many pickings. The fruits should be picked up daily in warm weather and 2-3 times a week under cold conditions. Picking operation should be completed before noon to avoid heating to berries. Picking should be done in the early hours to avoid spoilage during transportation and storage. After harvest, fruits should be kept under shade to avoid damage due to excessive heat in the open field. The strawberry fruits decay within 2-3 days of harvesting under natural conditions.
The taste of berry depends upon the sugar, acid and aroma which are associated with inherent characters and environment conditions. The berry is rich in vitamin C and its content increases as the ripening advanced. Sugar content increases and acidity decreases until berry attain full ripe stage. Sugar/acid and tannin ratio is termed as a good index for judging stage of ripeness.
The strawberry is a non-climacteric fruit. The respiratory peaks are reached at full to overripe stage. Senga Sengana variety takes 30 to 40 days from full bloom to maturity. Different varieties of strawberry produced an average yield 50 – 60 q/ha but higher yield upto 8 q/ha can be achieved. Still higher yield upto 250 q/ha may be achieved by following standard practices and growing recommended cultivars.
Pre-cooling of fruits at 4°C immediately after harvesting is very useful practice in extending life in cold store. The fruits after pre-cooling should be transported in refrigerated van for sending to the markets. The fruits should be packed in perforated CFB cartons with paper cuttings as cushioning material.
The fruits can be stored upto 10 days in cold storage at 32°F. The shell life of Senga Sengana variety at 6°C was found to be 8 days with 20 per cent carbon dioxide. The fruits stored at 3°C in oxygen or at 5 – 20 per cent carbon dioxide remained is good condition for 10 days. All the concentration of carbon dioxide reduced rotting due to Botrytis.