Everything you need to know about growing a plum tree! Learn about: 1. Botany of Plum 2. Origin of Plum 3. Climate and Soil 4. Orchard Cultural Practices 5. Propagation and Rootstocks 6. Pollination and Thinning 7. Planting Operation 8. Flowering and Fruiting 9. Training and Pruning 10. Harvesting and Handling.
Botany of Plum:
Plum belongs to the genus Prunus, the sub-family Prunoidae and the family Rosaceae.
The important species of plum are as follow:
1. Prunus Domestica L- European Plum
2. Prunus Salicina Lindl- Japanese plum
3. Prunus Insititia L- Damson plum
4. Prunm Cerasifera Ehrh- Cherry plum
5. Prunus Americana- American plum
European plum is used for making prunes and various products.
Japanese plum is most common plum for fresh production. Damson plum is used for preparation of Jam, Jellies and preserve. It is also used as a rootstock for plums. Cherry plum is also used as a rootstock. American plum are wild small trees and produce small edible fruits which are used for preparation of various products.
The Japanese plum is strong small tree with glabrous parts, mostly with brown shinning twigs. The leaves are oblong-obovate or oblong-ovate, not prominently rugose, abruptly but prominently pointed, closely blunt serrate, dull, usually shinning above and glabrous beneath. The flowers are white, two or three from each bud but appearing clustered on the spurs. The flowering starts in the second week of February and the tree come to full bloom after 7-10 days of first flower appeared.
The cyme with flowers is closely crowded on a very shorter peduncle and with pedicels of about equal length, hence, termed as cymose (Fascicle) inflorescence. The fruit-setting starts in the second week of March. It is a drupe or stone fruit and the exocarp is a thin skin. The mesocarp which is the edible portion is thick and fleshy. The hard stony endocarp contains seed.
Origin of Plum:
About 40 per cent of the area under plums in India is confined to Kashmir. Two types of plum are cultivated in India. European plums (Prunus domestica) are cultivated at higher elevations and are polyploids. The Japanese plums (Prunus salicina) are at lower elevations and in the sub-montane areas. Most of the European plums are self- fruitful, whereas the Japanese plums often require cross- pollination. The choice of varieties for planting should be made by keeping this fact in view.
However, the important Japanese varieties, Santa Rosa and Beauty, are self-fruitful, and can be planted alone. There are several varieties of plum. The important amongst them are Santa Rosa, Grand Duke, Beauty, Plum Red, Mariposa, Kelsey, Wickson, Burbank and Victoria. The prolific-bearing varieties of poor quality grown in the plains are Alucha Yellow, Alucha Red and Titron.
In Punjab local selections Kala Amritasari and Golden Lalri are promising. Exotic low chilling varieties introduced in Punjab are Fla-1-2 and Fla-1-2 (Sutlej purple) which is self-unfruitful but compatible with Kala Amritsari. Average yield Fla-1-2 is 30 kg/plant. Fruit colour turns bright crimson at maturity.
Plum is generally propagated by shield-budding on seedling of wild apricot (Zardalu) or on peach. On heavy sticky soils, plum root-stock is used. The cultural practices are similar to those for peach. Plum requires plenty of irrigation during the fruiting season. The bearing habit of the plum is variable.
Several varieties of European plum bear on spurs and require practically no pruning. The Japanese varieties bear a profuse crop on shoots and require more severe pruning. Pruning should be regulated in such a way that the tree makes 30 to 50 cm of extension growth every year.
In Himachal Pradesh, 10 kg FYM, 50 g N, 25 g P and 60 g K for every year age of plant upto 10 year with no further increase, has been recommended. Nitrogen is applied in two split doses, once in spring before flowering and the remaining one month later.
In the plains of Punjab, application of 200 g N, 75 g P and 200 g K per tree with a basal dose of FYM at the rate of 35 kg/tree is applied in December. Half of N with full dose of P and K one month before flowering and the remaining N after one month of fruit set are recommended.
The Japanese varieties require more fruit-thinning than the European ones. The variety Beauty requires most severe thinning and Santa Rosa only light thinning. Fruit-thinning is done in April and May before the hardening of the pits. DNOC (473 ml dissolved in 100 litres of water) is recommended for flower thinning and is sprayed at 60 to 75% full bloom stage. Carbaryl (Sevin) at 1000 ppm applied at full bloom stage also gives optimum thinning.
Unlike peach, the plums should be harvested when almost ripe to get the best fruit quality. However, for distant markets, the harvesting is done a few days in advance.
Climate and Soil Required for Growing Plum:
The cultivars of Japanese plum require comparatively less of winter chilling i.e. about 700 and 1000 hours below 7.2°C. Most of the Japanese plum cultivars are resistant to winter cold and thus can be grown in more northerly regions of the Northern Hemisphere. The bloom period of plum tends to get delayed on the northern slopes thus helping them to escape spring frost injury.
The Japanese plums do very well in the low and mid hill regions, ranging between 650 and 1650 metres above sea level. Plum require 100-125 cm of rainfall well distributed throughout the year for good growth and fruit production. A few varieties of Japanese plums with chilling requirement below 300 hours are also growing successfully in the sub-montane tracts of the Punjab and Haryana.
Some varieties of plum can be grown successfully even in the warmer region of the plains. This region is marked by an extreme summer temperature reaching 45°C and very low relative humidity that is abruptly changed in first week of July by arrival of cool monsoon rains.
In winter, the night temperature may touch 0°C with occasional ground frosts. Plants get 250 to 300 chilling hours. Plum orchards are prone to damage by high wind velocity and must be protected by planting wind break trees.
Cool winter and warm summers are suitable for its successful cultivation. The location of a plantation on the road-side, where adequate transport facilities are available, prove advantageous both in establishing the orchard and in disposing of the crop.
The Japanese plum can even do well on inferior soils having shallow water table and high pH. However, for good growth and longer life of the plants, well-drained medium to deep loam soil with pH between 5.5 to 6.5 is most suitable.
Availability of ample good quality irrigation water is of primary importance while selecting site for plum plantation. Plum trees will fail to produce commercially acceptable crop if they suffer from water deficit. Plum propagated on peach rootstocks grow better on sandy loam soils whereas the heavy and wet soils are suitable for plants propagated on Kabul Green Gage rootstock of plum.
Orchard Cultural Practices for Growing Plum:
i. Irrigation:
The water requirement depends upon the age and size of the tree, type of soil, climatic conditions and cultural practices being followed. The young plum plants upto the age of 3- 4 years need irrigation at 4-5 days interval during summer months starting from April to June.
The irrigation should be avoided during flowering and fruit-setting stage. During April and May frequent irrigations at an interval of 4-5 days should be given for proper development of fruit size and quality. Irrigation should be stopped at the colour break stage to avoid heavy fruit drop.
However, when there is rainless spell light watering may be given. In Santa Rosa plum, irrigation at 50% field capacity at an interval of 12 days in May and 8-9 days in June is considered beneficial for better yield of high quality fruits. In mid-hills six irrigations in a season are sufficient for plum orchard.
ii. Intercropping:
Intercropping can be successfully practiced during the non-bearing period of the trees and should not interfere with the fruit trees. Need-based manures and fertilizers, irrigation and plant protection measures should be given independently to the fruit trees and intercrops. The short-statured, shallow-rooted, leguminous crops like moong, mash, pear, gram, cluster been etc. can be sown as intercrops. Intercrops like wheat should not be sown in plum orchard as it need frequent irrigation during winter.
iii. Weed Control:
In plum orchard of Himachal Pradesh, several monocot weeds like Cyperus rotundus, Commelina nudiflora, Digitaria sanguinalis, Setaria glauca etc. and dicots like Amaranthus viridis, Chenopodium album, Medicago sp. etc. were recorded. Bromacil and atrazine at 2.5 to 7.5 kg/ha were found effective to reduce the weed population.
Terbacil at 3 kg/ha and simazine at 4 kg/ha in plum orchards also found effective in checking weed. Both these herbicides also increased N, K and Ca content of leaf. In 12 year old Santa Rosa plum orchard diuron and atrazine at 4 kg/ha in April as pre-emergence and gramoxone at 2 l/ha or glyphosate at 800 ml/ha as post-emergence proved effective in controlling weeds.
iv. Manuring and Fertilization:
The plum trees must be manured and fertilized judiciously for vigorous and healthy growth and optimum yield of good quality. In Punjab, for one year old plum tree, 6 kg farmyard manure, 30 g N, 15 g P and 36 g K is recommended. Similar amount of farmyard manure and chemical fertilizers should be fed every year up to the age of 6 years. Thereafter, the quantity of farmyard manure, N, P and K should be kept constant at 36 kg, 180 g, 90 g and 216 g, respectively. Farmyard manure as well as phosphatic and potassic fertilizer should be applied in December. The nitrogenous fertilizer should be split into two equal parts. Apply half dose of nitrogen in spring before flowering and remaining half one month later after fruit set.
At Ferozepur (Punjab) 200 g N, 75 g P2O5 and 200 g K2O resulted in largest and heaviest fruit in Kataru Chak cultivar.
In Himachal Pradesh, one year old plum is given 70 g nitrogen, 35 g phosphorus and 100 g potash besides 10 kg of FYM. Thereafter, the dosage are increased at the rate of 70 g N, 35 g P, 100 g K and 5 kg FYM for each complete year of plum trees in the orchard. The fertilizer dose are stabilized at the age of seven years and 40 kg FYM, 500 g N, 250 g P2O5 and 700 g K2O is applied to per plant.
In Jammu and Kashmir, plum trees of 10 years age and above are applied 450 gN, 150 g P2O5 and 750 K2O per plant.
Foliar application of urea @ 0.5-2.5 per cent for correcting nitrogen deficiency have been reported.
Zinc Deficiency:
The deficiency of zinc is frequently observed in plums growing in sandy soils during the summer month. Leaves on terminal parts of branches become narrow, small with interveinal chlorosis. On growing tips, leaves show rosette form. The deficiency cause dieback of twigs and fruits become hard and tough. It can be corrected by foliar sprays containing 3 kg zinc sulphate and 1.5 kg unslaked lime in 500 litres of water as and when the deficiency symptoms are observed on plants.
Boron Deficiency:
Due to boron deficiency fruits remain small and misshapen. Corky spots develop on fruits and they cracks. Leaves become dark green and boat like. Terminal buds fail to develop. Under severe deficiency, die back of shoots occur. The deficiency can be corrected by spraying 0.1% Boric acid in June.
Propagation and Rootstocks of Plum:
Plums are generally propagated through hard-wood cuttings. In case rootstocks are to be used, budding and grafting method are employed for its propagation. Plum is raised on seedling root stock of wild apricot (Zardalu) and Myrobalan B (Prunus cerasifera) clonal rootstock. In Punjab, the cuttings of ‘Kabul Green Gage’ plum are used as rootstock for heavy and wet soils.
The peach seedlings are recommended for sandy loam soils. Myrobalan B is mainly multiplied through mound layering. This rootstock can also multiplied through hard wood cuttings treated with 2500 ppm IB A for 10 seconds and planted in open field during January – February.
Raising of Rootstock:
(a) Through Seed:
In Himachal Pradesh, the seeds of wild apricot (Zardalu) are collected from fully ripe fruits. After drying, the seeds are treated with Bavistin @ 3 kg/kg and stored at temperature of 38 – 45°F and RH 20 per cent. In order to break dormancy, the seeds are stratified in moist sand for 45 – 50 days in 30 – 45 cm deep pits dug in cool and shady place in January. Water soaked seeds are put in 3 – 4 cm thick alternate layers of sand and kept moist during the period of stratification. The stratified seeds are sown in nursery beds at a depth of 6-10 cm in rows 25 – 30 cm a part with a distance of 10 – 15 cm from seed to seed.
After sowing, beds are covered with 10 cm thick hay mulch to protect the germinating seedlings from direct sun, heavy rains and spring frost. Light irrigation is given after sowing to avoid desiccation of stratified seeds. When seedlings attain a height of about 5 cm hay mulch is removed. In one year about 90 per cent seedling become buddable.
In Punjab, the plum stones are extracted from the ripe fruits and stratified in die field or in the wooden boxes. For field stratification, the seeds are sown during November in rows 30 cm apart and distance of 60 cm is left after every two rows. The seeds within a row are sown at a distance of 10 cm. Stratification of seeds in the boxes is done in the beginning of December by keeping the seeds and moist sand in alternate layers. The sand should be kept moist without making it too wet or saturated. Stratification can also be done in shallow pits dug in the field.
The seed in these can be placed in alternate layers with moist sand. The pits should always be prepared at a higher level, so as to avoid chances of accumulation of water which reduces the seed germination. Stratification is complete when the hard shell is broken and the plumule has emerged from the stone.
The stratified seed is sown during the end of January or first week of February in rows 30 cm apart with seed to seed distance of 10 cm. The light irrigation should be given immediately after sowing the seed.
(b) Through Cuttings:
Plum rootstock can be propagated from stem cuttings. For this purpose, cuttings of Kabul Green Gage plum are prepared during the first week of December and are kept for callusing for about a month. These are planted in the beds preferably during the first fortnight of January. The cuttings are planted at a distance of 15 cm in rows which are 30 cm apart. The rooted cuttings are budded in the following May-June or grafted in December-January.
(c) Clonal Rootstock:
Myrobalan B is multiplied through mound layering (stooling). The rooted layers of clone are planted in well prepared stool beds in December at a distance of 30 cms in rows and 60 cm apart. Numerous suckers come out from the layers are covered by 2 – 3 soil mounding before monsoon. Suckers are ringed near the base during rainy season and treated with 750 ppm 1BA for quick and better root initiation. Rooted layers are separated in December and lined out in nursery buds for further grafting.
Vegetative Propagation:
i. Hard Wood Cuttings:
The rooted cuttings of Kala-Amritsari cultivar can be used directly without budding. The percentage of their successful establishment can be enhanced by dipping the basal portions (5-7.5 cm) of hard-wood cuttings for about 24 hours in 100 ppm solution of IBA. The cuttings taken from sub-apical portions, planted after dipping in IBA and callusing for about a month give higher percentage of success. The time of preparation of cutting is from end of December to end of January.
ii. Budding and Grafting:
Budding by shield or T method is performed in April and July- August. The plants budded in April become saleable in January but those budded in July- August can only be sold after one and half year i.e. next January.
The propagation by cleft and tongue grafting is performed when the stock and scion are still dormant (December-January). Cleft grafting is generally performed when the stock is thicker than the scion. The rootstock which is left while budding during July-August can be grafted in the coming January which will be ready for sale in the next winter. In Himachal Pradesh, grafting is done in February. Chip budding done during mid-February also gives good success.
iii. Simultaneous Grafting/Cuttings:
The plum can be propagated simultaneously by grafting on un-rooted cuttings of Kabul Green Gage by dipping the basal portion of cutting in 100 ppm solution of IBA for 24 hours during first fortnight of January. The plants from the cutting/grafts are available for planting after one year in the month of January.
Pollination and Thinning:
The Japanese plum cultivars grown commercially require pollination to set satisfactory crops. Most Japanese plum cultivars are self-unfruitful and require cross-pollination. Some cultivars like the Santa Rosa and Beauty are partially self-fruitful and may bear heavier crops when planted among other cultivars.
Self-fruitfulness is not a constantly stable character and may vary from year to year and area to area. The cultivar Santa Rosa is self-fruitful in India and in some areas of the USA, where it gives heavy yield when planted in solid blocks. However, in some northerly located areas of California, and Canada, Santa Rosa requires cross- pollination by bees from other cultivars..
Kala-Amritsari is the most widely grown plum cultivar in sub-tropical areas. It is a self- fruitful but in controlled pollination studies its yield improved up to 23 per cent when pollinated with Titron. Kataru Chak is partially self-fruitful cultivar but the yield improved up to 13 per cent if pollinated with Kala-Amritsari.
Fruit set by open pollination ranged between 15.3 per cent in Kataru Chak to 27.8 per cent in Kala Amritsari. Fruit set by self-pollination is reported 11.6 per cent in Kala-Amritsari and 8.2 per cent in Kataru Chak.
To improve the prospects of the plum cultivation, it is essential to improve the marketable size and quality of the fruits. There is generally excessive fruit set in plum. If all the fruits are retained on the tree, their size as well as quality may deteriorate and such small sized and poor quality fruits may not fetch good price in the market.
Thinning is more desirable on mature trees making small annual growth than on young vigorous plants. Trees growing on light soils, deficient in moisture and nutrients, would also need for fruit thinning. The Heavy bearing cultivar of plum like Kala Amritsari normally need fruit thinning to minimise the danger of limb breakage.
Thinning may also be resorted when good sized uniform fruits are needed for canning industry and fancy trade. Thinning should be done after natural fruit drop in April. This operation should be completed before the hardening of the stones within fruits.
Hand thinning is commonly practiced. In this, first shake the branches slightly in order to dislodge the fruits which are likely to drop off naturally. If there is still surplus fruit, then start thinning from top to the bottom of the branches. Hold the stem of the fruit to be removed between thumb and second finger and pull it off gently.
The main point to be kept in mind while thinning is to remove all the small, undersized, misshaped, insect or disease attacked fruits. For obtaining well coloured fruits of good size, the retained fruits should have a spacing of 5-8 cm apart depending upon variety.
Foliar spray of 200 ppm ethephon and 1000 ppm carbaryl at full bloom is very effective for blossom thinning.
Planting Operation for Plum:
The plants do not need any earth ball and are lifted from the nursery with bare roots. They can be lifted with the help of a spade by digging deep trenches. The soil sticking to the roots should be removed by shaking the plants gently. Trimming of the exceptionally longer roots is done to avoid injury during transportation. These plants are then tied in bundles of suitable sizes for easy handling. Plants of one years’ growth after propagation should be preferred, as fewer roots are injured in the processes of lifting and replanting and the desired framework can be attained by heading back the tree from required height. Trees older than two years should not be selected for planting.
Plums should be planted in January when the plants are in the dormant condition. The area is laid out and pits of 1 M x 1 M x 1 M are dug about a month before planting.
Pits are refilled with fertile top-soil mixed with 40 kg of well-rotten farmyard manure per pit. Add 15 ml of chlorpyriphos 20 EC mixed in 2 kg soil to each pit to prevent attack of white ants. Apply irrigation soon after setting the plants in the pits. The plum plants may be planted 6 metres apart from row to row and plant to plant in square system, thus accommodating 275 trees per hectare.
Plum is also planted as a filler trees is mango, litchi and pear orchards during the first fortnight of January. The plants of Kala Amritsari are also transplanted in the orchard of Satluj Purple as pollinizer in the ratio of 25: 85 plants per acre. Alternate plants of pollinizer are planted in the every second row of Satluj Purple for effective pollination and improving fruit set in orchard.
High Density Planting:
Satluj Purple plum trees can also be planted at 6 x 1.5 m distance with modified leader system and summer pinching (10 – 15 cm). This practice ensure high yield of better quality fruits.
Care of Young Plants:
The newly planted young plants, being very tender, need lot of care and attention for their better survival and growth. They should be watered at frequent intervals. However, heavy irrigation should be avoided as stagnation of water in their basins may do more harm than good. The main stem should be cut back to the desired height for the scaffold branches to develop properly and to keep proper balance between the root-system and the growth of the stem.
The young plants need staking so as to make them grow upright and straight. The supports should be of bamboo or other wooden logs and should be well fixed in the soil. The lower portion of their trunk should be white-washed to afford protection against sunburn. The provision of a thick row of tall trees alternating with small ones as effective windbreaks is very essential in order to check the adverse effect of strong winds.
Flowering and Fruiting in Plum Trees:
The flowering in Japanese plum in Himachal Pradesh varied from 11-17 days which started on 5 March and ended on 21 March. In most of the plum varieties grown under sub- tropical conditions flowering starts in the second fortnight of February and last upto first week of March.
Alu Bokhara is the late flowering varieties and bloom in the first fortnight of March. The presences of abnormal and imperfect type flowers do not materially affect the cropping as about 90 per cent of the flowers are hermaphrodite.
Pollen viability and germinability ranged from 30 to 90 per cent and 30 to 70 per cent respectively in different cultivars. The stigma become receptive one day before anthesis and remained so till three days after.
The growth pattern of plum followed a double sigmoid curve. The fruit weight continued to increase and specific gravity decreased from fruit set till maturity. As the picking season advanced an increase in the total soluble solids with a corresponding decrease in the acidity of the fruit was observed.
Training and Pruning of Plum:
The plum plants are trained according to growth habit of varieties and vigour of the root stock. Generally, plum trees are trained to open centre system. In sub-tropical climate, the trees are trained according to modified leader system and the plant is headed back to the height of 90 cm ground the level after planting in the field. The plants sprout in February and produce numerous shoots during spring and summer months and continue growing until about the beginning of October. During the first dormancy of the plants in the field, select 4-5 laterals which are usually quite satisfactory but the one most favourably located around the main stem to make a proper framework.
The remaining branches present on the central axis should be removed. At this stage, the central terminal branch is called the leader. The lowest branch on the stem should be about 45 cm from the ground. During second year, plant grows in height, produces secondary branches on the selected primary limbs and new branches above the first year extension. The training imparted to the third year old trees is designed to maintain the proper balance between the main scaffold limbs and secondary branches.
The position of the laterals maintained during the previous growing season should not be disturbed during the third growing season. During this period water sprouts arid undesirable twigs should also be removed. During fourth year, the leader should be headed back at a point where a suitable outgrowing lateral is present so as to check the height of the plant.
In open center system, the top of the plant is headed back to 60 cm at the time of planting to stimulate the growth of lateral branches. During first summer 3-5 scaffold branches around the main stem are selected. The lowest scaffold should be about 30 cm above the ground level and the others scaffolds should be 15 cm apart in spiral order. In the first dormant pruning, the central leader is headed back and scaffold branches are allowed to grow whose about one- third growth is removed.
In second dormant pruning 2-3 well spaced branches are selected on each primary scaffold whose one-third to one-fourth portion are pinched off. In third year, training consists of heading back and thinning of unwanted branches. Training is completed in fourth year and only light pruning with heading back of branches is done.
Plum bears on one-year growth as well as on short spurs. To encourage fresh growth and to maintain a system of healthy spurs, light annual pruning should be done in January. It consists of the removal of thin and crowding twigs and branches within the tree.
Criss-crossed, lengthy branches, dried and diseased branches should be thinned out to admit sunlight in the tree centre for the development of better colour of fruits. Besides, water sprouts or suckers arising from the crown part of the tree should also be cut regularly. After every 4-5 years of fruiting, heavy pruning of the tree is done by heading back the lengthy branches about half of their length.
In Himachal Pradesh, Santa Rosa plum require 25-30 cm annual extension growth for proper fruiting which consists of 25-30 per cent thinning along with 1/3 to 1/2 heading back of shoots.
Harvesting and Handling of Plum:
Plum is a delicious fruit which ripens during summer months when other kinds of fruits are not available in plenty. It is a climacteric fruit and does not attain full ripe edible quality on the tree at harvest. Fruits should be picked at proper stage of maturity. It is precocious and starts yielding fruits within 2-3 years of planting.
The fruit reaches ripe stage in 12 weeks after fruit- set. The peak season for plum harvest in sub-tropical climate is from first week of May to end of May in different varieties in Punjab and adjoining areas and June-July in Himachal Pradesh.
On the basis of days from full bloom (DFFB), picking dates of plum can be standardized. The optimum picking of cv. Santa Rosa is determined 94 ± 3 DFFB. The varieties like Beauty, Frontier and Alu Bokhara should be picked after 87 ± 2, 108 ± 2 and 102 ± 2 DFFB, respectively. Such predictions would be valid for areas with relatively constant summer temperature or for species in which very high summer temperatures do not hasten fruit maturity.
Harvesting of Kala-Amritsari plum around 4th June i.e. after 84 days of fruit set under sub-tropical conditions of Abohar is suggested. At that time TSS should be around 13.0 per cent. The best indices for judging the maturity of plum are that specific gravity should be less than one with deep purple red colour of the fruits in Titron and Santa Rosa and light brown in Kala-Amritsar.
Plum fruits should be picked at ripe but firm stage from the tree for local consumption. However, for distant market, fruits are picked when these have developed 50% colour on the skin and should be firm. This keeps them in good condition during transportation and reach in the market in a firm and attractive condition.
The grown up tree of plum yield about 30-50 kg of fruits per tree in sub-tropical climate and 60-70 kg of fruits in mid-hills.
Plum fruits are picked with hand in several pickings, as the entire crop does not ripen uniformly at a time. While picking care should be taken that spurs are not damaged. Care should also be exercised not to tear the flesh of the fruit or to destroy the natural bloom.
If the fruit is jerked in a direct pull from the spur, the fruit stalk may get torn out and the flesh may become ruptured. While picking the fruit give a gentle twist and let the stalk remain attached to it. Never permit threshing of branches with sticks for facilitating harvesting. Small baskets lined with Paper cloth or polythene should be used for placing the fruit during harvest.
The grading should be regularly practiced for getting market value of the fruit. Before packing sorting should be done to remove under-ripe, under-sized, over-ripe and damaged fruits. Plum fruits are graded according to fruit size in 3 grades under Agmark system of grading.
The fruits should be packed for sending to the distant market immediately after picking as plum fruits soften rapidly after picking. The fruits should be packed in 5 kg wooden boxes instead of, in bamboo baskets to avoid losses in transportation.
To prevent the fruits from injury, interior of wooden box should be lined with newspaper sheets on all sides and paper strips as padding at the bottom. The fruits are placed in layers. After each layer make a partition of paper strips over lined with newspaper sheet. Top layer of the fruit is covered with a cushion of paper strips and newspaper sheet and finally the lid of the box is nailed.
Shelf Life:
The perishable nature of ripe plum fruit poses a serious problem for its storage, transport and marketing. The main reason for its limited cultivation in the subtropical areas is the poor keeping quality of its fruit. Storage in a fresh condition for extended period without loss in quality is, therefore, very pressing problem. Effective preservation in fresh condition is mainly governed by harvesting of fruits at right stage of maturity and post-harvest treatments.
The ripe fruits of Kala-Amritsar plum could be stored for 4 days in paper bags at room temperature after treating with 3-6% wax-emulsion. The fruits remained in good conditions upto 30 days in the commercial cold storage (temperature 30-35°F with relative humidity of 85- 90 per cent), when treated with 3-6 per cent wax-emulsion for 30 seconds and stored in perforated polythene bags of 100 gauge thickness.
Post-harvest dip in 4% CaCl2 for 2 minutes increase the storability to Santa Rosa for 12 days at ambient temperature. Fruits of Kala-Amritsari plum can be stored for 55 days and of Satluj Purple for 30 days in the commercial cold storage (temp. 3.3°C and RH 85-90%) after treating with 10 ppm GA3.
The Satluj Purple plum fruits harvested at colour break stage, followed by post-harvest treatment of calcium nitrate (2%) solution for 5 minutes, can be stored for 4 weeks in cold storage (0 to 1°C temp at 90 – 95% RH) with post storage shelf life of 2 days at ambient temperature.