Everything you need to know about growing a papaya tree! Learn about: 1. Botany of Papaya 2. Climate and Soil Required for Growing a Papaya Tree 3. Orchard Cultural Practices 4. Propagation 5. Planting Operation 6. Flowering and Fruiting 7. Sex Expression and Identification 8. Harvesting and Handling 9. Diseases and Insect Pests.
Botany of Papaya:
Papaya belongs to the family caricaceae- a small, somewhat anomalous family with 4 genera and 31 species of which three are in tropical and subtropical America and one in Africa. The genera and the number of included species are, Carica- 22, Facaratia- 6, Farilla- 1 and Cylicomorpha- 2. The edible fruits are found only in Carica papaya. Other species include Carica chilensis, Carica goudotiatia, Carica monoica and carica pubescens. Carica candamarcensis (mountain papaya) grows to a height of about 2.4 m, can withstand low temperature and thrives well at an elevation between 1500-2000 m.
Papaya is dioecious but hermaphrodite forms occur. The stem is hollow and soft-wooded. It is usually un-branched while young but at later stage upright shoots are developed on its terminal growth due to its obstructions.
The leaves are palm like with long stalked. Flowers are fragrant axillary panicles. The fruit is fleshy berry. The shape of fruit from pistillate flower is ovoid-oblong to nearly spherical and from hermaphrodite flower it is pyriform cylindrical or grooved.
The skin of papaya fruit is smooth, colour is green but turning yellowish or orange when ripe. Flesh is orange or reddish orange, sometimes it is yellowish in colour, central cavity 5 angled. Seeds are many in a fruit depending on climatic conditions and variety. The seeds are spherical in shape, black or greyish, wrinkled enclosed in gelatinous sacrotesta formed from the outer integument. About 20 seeds weigh one gram. Botanically, the fruit type is berry and mesocarp is the edible portion of the fruit.
Climate and Soil Required for Growing a Papaya Tree:
Papaya is a tropical fruit. It requires warm and humid climate and can be cultivated upto height of 1000 metres above sea level. The temperature below 10°C affects adversely on growth and development of fruits, thus delayed maturity and ripening. At this temperature, the fruits cannot develop flavour and also causes poor taste. Dry climate characterised by a meagre rainfall tends to add to the sweetness of fruit whereas wet climate with heavy rainfall tends to reduce the sweetness.
Papaya can be grown successfully all over plains of north India. However, areas free from frost during winter and scorching heat and desiccating winds during summer are highly suitable for its cultivation. Young plants must be well protected against frost. They should be covered with transparent plastic envelops, Sarkanda, straw thatches or any other covering material from November to February against frost damage.
Papaya cannot tolerate hot summer or frost. The optimum range of temperature is 22-26°C for papaya. Annual rainfall should range between 1500 to 1800 mm and it should be evenly distributed. It cannot stand in water-logged conditions and need protection against winds. For successful cultivation, papaya requires comparatively high temperature coupled with low humidity and adequate soil moisture.
Papaya can be grown on a wide range of soils but for better results, a well-drained soil, rich in organic matter is desirable. It is a shallow-rooted plant, highly sensitive to wet feet. Water stagnation, even for a short time, may kill the plant.
Hence soils with shallow water table or which are subject to stagnation of water should be avoided. Medium black and alluvial soil are also suitable. The pH of the soil should be within 6-7. Generally, calcareous and stony soils with poor organic matter are not suitable.
Orchard Cultural Practices for Growing Papaya:
i. Irrigation:
Adequate irrigation helps in rapid fruit development and also to obtain regular fruit yield. Papaya cannot tolerate wet feet. Heavy irrigation should, therefore, be avoided as otherwise the papaya trees may suffer from root-rot. In well drained soils, irrigation at shorter intervals during the early crop stages results in good establishment and also encourage better plant development.
Generally, papaya crop is irrigated at 4-5 days intervals in summer and 8-10 days in winter depending upon climate and soil conditions. The ring system of irrigation is better because it prevents irrigation water from coming into direct contact with the stem, thus preventing collar rot.
ii. Intercropping:
The short duration vegetables like radish, tomatoes, cabbage, cauliflower, onion, chilies can be grown as intercrops during the pre-bearing period. The intercrops should be maintained in such a way that they are competing with the main crop. No intercrop should be grown when the plants are in bearing stage. Papaya itself is a popular intercrop with fruit trees. In mango, litchi and pear during first 6-7 years, one or two rows of papaya between the tree rows can be grown profitably. Papaya does not interfere with the main crop because it produces the fruits only for 2-3 years.
iii. Weed Control:
Weeding is necessary and should be done regularly to keep the field weed free. In the field with grown up plants, the inter-space remains covered well with the top growth which helps in checking weeds. Two hand diggings one in the beginning of rainy season and other in January-February are necessary for papaya plantation every year. Application of fluchloralin or butachlorine @ 2kg/ha as pre-emergence herbicide two months after transplanting check the weeds for 4 months.
iv. Manuring and Fertilization:
Papaya is a heavy feeder and responds well to fertilizers. In Punjab, the plant is manured @1.25 kg of fertilizer mixture i.e., Urea, superphosphate and muriate of potash in the ratio of 1:2:1/3 twice a year i.e., during February and August. Well rotten farmyard manure is applied @ 20 kg per plant every year in December.
A fertilizer trial conducted at IIHR, Bangalore showed the importance of all the three nutrients for high yields. But the effect of phosphorus on yield was pronounced than that of either nitrogen or potash. 500 g of potash per plant/year was the best fertilizer dose and 250 g of each nitrogen and phosphorus gave a yield of 186 tonnes per hectare in the crop life of 28 months. This dose was applied in six split applications.
Propagation of Papaya:
Papaya is propagated entirely from seed. The conventional methods of vegetative propagation like cuttings, grafting, buddings etc. have not proved useful for one reason or the other. Seeds used for raising the seedlings should be fresh as their viability is lost in about 45 days. The seedlings can be raised both on raised beds in polythene bags.
i. Preparation of Seed-Bed and Raising of Seedlings:
The seedbeds are prepared on well-drained soil where the farmyard manure is thoroughly mixed. Generally 40 sq. meters area is sufficient to raise seedlings for transplanting one acre and for this much area one quintal of well rotten farmyard manure is recommended. The seedbed should be 2 meters long, 1 meter wide and 15 cm high above the ground level.
The seeds are sown in the second week of July to third week of September. However, the nurserymen should sow the seed in two, three lots of 15 days interval. This will help in regulating the plant sale.
Seeds before sowing are treated with 3 g of Captan per kg of seed. About 150 g seed is enough to raise seedlings for one acre. The seeds are sown 2-3 cm deep and 15 cm apart. The distance from row to row is also kept 15 cm. A light irrigation is given immediately after sowing the seed. Give the subsequent irrigation when the beds are still in ‘vatar’ condition.
ii. Aftercare and Transplanting of Seedlings:
The seeds germinate in 2 to 3 weeks. When the seedlings have emerged, drench the nursery beds with 0.2 per cent Captan (200 g in 100 litres of water) to prevent the damping off young seedlings. Repeat the drenching of nursery- beds after 4 days, if necessary.
One month after the emergence, the seedlings attain the height of about 15 cm and they are recommended for transplanting in the field.
Top dressing of seedlings in nursery with urea or ammonium sulphate should be avoided as this encourages damping of disease and the development of tall and lanky seedlings which are not suitable for transplanting.
iii. Raising the Seedlings in Polythene Bags:
Papaya seedlings raised in polythene bags can stand transplanting better than those raised in seed beds. Perforated ploythene bags of 25 x 10 cm size with 100 gauge thickness can be used for sowing the seed. About 8 to 10 holes of 1 mm diameter are made on the lower part of the polythene bags for drainage. These bags are filled with a mixture of farmyard manure, soil and sand in equal proportion. Two or three seeds are sown in one bag and after germination only one seedling is retained.
These seedlings in the polythene bags should be treated with Captan (0.2%) after their emergence. The transplanting in this case is done along with polythene bags. Only care taken in this case is that the bags should be ruptured at the bottom while transplanting.
Planting Operation of Papaya:
The best time for papaya planting is either July-September or February-March. After through preparation of land, pits measuring 50 cm x 50 cm x 50 cm should be dug out at spacing of 1.5 m x 1.5 m (4400 plants per hectare) and kept exposed for a few days. These should be refilled with a mixture of top soil and well rotten farmyard manure. To each pit add 10 ml of chlorpyriphos 20 EC mixed in 2 kg soil as protection against white ants. When the seedlings have attained a height of 15-25 cm, transplant three seedlings per pit (10-15 cm apart) and apply irrigation.
After flowering, which usually takes place within 5-6 months, only one female or bisexual plant per pit is retained. Rests of the male plants are pulled out. However, well scattered male plants (one for every 10-15 female plants) may be retained for pollination purposes.
The planting distance of 2.5 to 3.0 metre is also recommended. The varieties like Co-1, CO-2 and Solo at 1.8 x 1.8 m, Coorg Honey Dew and Washington at 2.4 x 2.4 m and Pusa Nanha at 1.25 x 1.25 m distance can be planted.
Flowering and Fruiting in Papaya Tree:
The species Carica papaya is found to flower throughout the year. The inflorescence is axillary in position. Peak anthesis was found between 5 and 6 AM. The stigma receptivity was found to be maximum on the day of anthesis. The inflorescence of Washington papaya emerged 45-48 days after transplanting. The male flower appears in the axil of the 24th leaf and that of female in 18th to 20th leaf.
Female and male flowers developed within 32 and 42 days, respectively, after bud initiation. The flower opened between 8 and 11 A.M. Anther dehiscence was completed within 18 to 36 hours before the flowers opened and the stigma become receptive a day before the flowers opened, remaining receptive for 6 days.
The pattern of fruit growth in papaya followed the double sigmoid type. Depending upon the cultivars, the papaya took 145 to 165 days to attain ripe stage from the date of flowering. The colour break stage was characterised by an increase in vitamin A and proteins.
Sex Expression and Identification in Papaya:
Sex expression in papaya is very complicated phenomenon. Storey identified 8 working categories as staminate, teratological staminate, reduced elongata, elongata, carpelloid elongata, pentandria, carpelloid pentandria and pistillate. He further stated that Carica papaya has 3 basic sex forms viz. Staminate, pistillate and andromonoecious.
The pistillate plant is stable, while staminate and endromonoecious plants may be either phenotypically stable or phenotypically ambivalent going through seasonal sex reversals during which they produce varying proportions of staminate, perfect and pistillate flowers. Staminate flower is produced by male plant. Teratological flower is produced by sex reversing male plants. Reduced elongata, elongata, carpelloid elongata, pentandria and carpelloid pentandria are produced by hermaphrodite plants. Pistillate flower is produced by female plant.
Changes in the sex expression are accelerated by environmental factors such as low temperature to produce perfect flowers on the male plant. Fertile hermaphrodite types also have some pistillate flowers which may show male tendency in summer and female tendency in winter. A large difference between day and night temperatures can produce more female flowers than normal. Long day and high temperature has been reported to promote the formation of female flower in Coorg Honey Dew.
The application of growth regulators has been found to change sex in papaya. GA3 spray at 50 ppm in Co-1 increased the femaleness. It was reported that SADH treatment proved very effective in Co-1 for the control of height, acceleration of flowering and fruiting at lower node, increase in fruit set and yield.
TIBA100 ppm spray to papaya seedlings increased the femaleness. Application of GA3 on Coorg Honey Dew increased the production of hermaphrodite and staminate flowers, caused a two fold increase in vitamin C contents but reduced the seed number, fruit size and pectin content.
Ethephon @ 240-960 ppm and chlorflurenol @ 20-80 ppm induced intersexual and female flowers as well as male flowers on genetically male plants of Honey Dew cultivar. GA at 25 ppm and ethrel at 100 ppm on 100-125 days old seedlings tended to produce more females. Defoliation has been reported to induce maleness.
Sex Identification in Papaya:
It is difficult to identify the correct sex in dioecious type of papaya varieties until their floral emergence.
The use of peroxidase enzyme system for the identification of sex in papaya was tried at Cuba. Peroxidase zymogram patterns established by polyacrylamide get electrophoresis of extracts of leaf, petiole and root tissues from adult plants of 4 clones differed with sex of the plant and a similar differentiation could be recognized in Juvenile plants. More bands were present in the zymograms of male plants than the female plants. On this basis, hermaphrodite plants may not always be distinguishable from female plants.
The results of sex expression in Bangladesh revealed that the level of most amino acids has been similar in both male and female except for proline which is present in female plants only and cysteine which is absent in female plants. The level of tryptophan in female has been twice as high as in male plants.
Protection against Frost:
Papaya is very much susceptible to frost damage during winter. It is, therefore, utmost necessary to provide adequate protection against frost in winter under north Indian conditions. This can be done by covering the plants with rice straw or Sarkanda thatche or with white polythene bags of the size of plants in first winter. In home gardens, protection against frost hazard can be provided by planting papaya trees sheltered by walls. Furthermore, papaya plantations need to be protected against strong winds by providing effective windbreaks of Shisham, popular, etc.
Harvesting and Handling of Papaya:
Papaya trees tend to set too many fruits. Such crowded fruits do not get proper space and light resulting in their poor development and poor quality. Thinning of fruits while they are still of small size, is therefore advisable, so that the remaining fruits develop to proper size and are of good quality.
Papaya trees set fruits within 8-10 months of their planting. In another 4-6 months, depending upon the season, the fruits develop to proper size. In North India, fruits ripen during spring and summer. In hills, it is restricted to three to four months from February to May, because it requires a warm climate during ripening.
High humidity and comparatively high temperature during ripening period may not be conducive to development of attractive colour in fruits which may remain pale green even when ripe. When fruit attains ripening, the colour changes from green to yellowish green. To avoid bird damage, harvest the fruits immediately when mature. The fruit is considered ready for harvesting when the latex of the fruit becomes almost watery. Papaya is a climacteric fruit. The individual fruit is harvested with hands. Fruits are not allowed to fall on the ground or come in contact with the soil while plucking.
The yield of papaya varies considerably due to fertility of the soil, cultural practices and variety. The average yield ranges from 30-50 kg per plant. An average yield of about 40-50 tonnes per hectare in the first year and about 20-25 tonnes per hectare in the second year in obtained.
After harvesting, the fruits to be consumed locally should be stored in a single layer of straw until they become mellow. For distant transport, it should be packed in bamboo baskets with rice straw to avoid bruising. The fruit becomes suscpetible to fungal disease like- Colletotrichum gloeosporioides. It can be checked by immersing the fruits in hot water (50°C) for 20 minutes. Papaya fruit was classified as climacteric. It can be ripened artificially by dipping the fruits in 500 ppm ethephon during the end of December under Punjab conditions.
The fruits attained golden yellow colour after 4 days of treatment. The ripening was characterised by an increase in the activities of invertase, cellulase, pectinmethylesterase, catalase, peroxidase, adenosine triphosphatase, acid phosphatase, polyphenol oxidase and mitrochondrial glutamate dehydrogenase and falling levels of amylase, ribonuclease, mitochondrial adenosine triphosphatase, NADH diphorase and malic dehydrogenase and of the RNA, DNA; protein and mitrochondrial protein contents.
Room temperature (28-30°C) was found to be practically unsuitable for storage of fruits. A temperature of 20°C was found optimum both for ripening and satisfactory storage. The fruits get susceptible to fungal attack above 20°C, whereas, the onset of climacteric was delayed at lower temperature. Controlled atmosphere storage in 2% oxygen and 98% nitrogen at 10° C has been found to extend the storage life by a few days. Post-harvest decay of papaya fruit can effectively be prevented by dipping the fruits in Aureofungin at 1000 ppm.
Diseases and Insect Pests of Papaya:
The common diseases of papaya are:
(i) Stem rot, foot rot and collar rot caused by Pythium spp., which can be controlled by cutting off the infected parts, painting with an antiseptic solution, namely, 4% or 5% solution of Lysol or 50% Carbolic acid, protecting with coal tar and providing proper drainage.
(ii) Leaf curl caused by virus, which can be controlled by improving drainage and destroying, affected plants.
(iii) Fruit rot caused by Gloeosporium spp., which can be controlled by spraying with Burgundy mixture.
(iv) Mildews caused by Oidium caricae and Ovulariopsis papayae affect leaves.
The common insect pests of papaya are:
(i) Stem borer (Dasyses rugosellus), which can be controlled by cutting and destroying affected parts.
(ii) Fruit flies (Dacus diversus and D. cucurbitae), which can be controlled by poison bating, by keeping in flat containers a poison baiting, by keeping in flat containers a poison bait (20 g Malathion 50% W. P. or 50 ml of Diazinon + 200 g of gur or molasses in 2 litres of water).
(iii) Ak Grasshopper (Poecilocerus pictus), which can be controlled by spraying 0.1% BHC + 0.1% DDT (W.P.).
(iv) Cotton whitefly (Bemisia tabaci), which can be controlled by sowing resistant varieties, by spraying the crop fortnightly with 0.02% Phosphamidon, Monocrotophos, Methyl demeton, starting with the appearance of the pest (2-3 sprayings may be necessary).