Commercial Cultivation of Rose (Rosa hybrida)

The Life Of Roses

Family: Rosaceae

Introduction: Rose is the topmost commercial cut flower crop in the international market. It is the most widely grown and traded cut flower. It is acclaimed as Queen/King of flowers. Roses can be cultivated on open land, but for cut flower production these are grown under controlled conditions of the greenhouse and the flowers exhibit the best quality attributes required for the market. The plants are perennial thorny bush. The present day rose (Rosa hybrida) combines all desirable qualities such as productivity, attractiveness of bud, fragrance, a variety of colours and forms of the typical species of Rosa.

Cultivars:

Red: Upper class, Passion, First Red, Grand Gala (thornless), Red Torch

Yellow: Galileo, Royal Yellow, Taxi

Pink: Upper Class Pink, Adamma, Billie Jean

White: Peaceful

Green: Dubai, Tendaji, R.chinesis viridiflora

Blue: Applause (genetically engineered)

Propagation:

Commercially roses are multiplied by T-budding and stenting. Some root stocks are Rosa indica, Rosa multiflora, Rosa canina and Natal Briar.

Methods of propagation

1. Budding It is the most popular and successful method for multiplying roses. It provides a larger number of plants than cuttings, layering or grafting, as a single shoot of the desired scion furnishes a number buds for budding. Rooted cuttings of stock or seedlings with roots are used as wks. Budding is done 25-30 cm above the ground level. On the selected rootstocks, the buds are inserted into a T-shaped incision and then tied with suitable wrapping material or pothylene sheets /tape, adhesive tape, binding rubber strip. It takes 3-4 weeks for the bud to make a union. The new shoots from top portion of stock above the union are cut off and the polythene tap is removed.

 

2. Cutting Propagation of roses by cuttings is done to raise root stocks for grafting or budding. This method is also used for multiplying vigorous types of cultivars, domestic roses and all other landscape roses. Climbers, ramblers, polyanthas and miniature roses does quite well by this method. This is the easiest and least expensive method. Usually one season old matured cuttings with 12-15 cm length (3-5 nodes) of pencil thickness should be used as cuttings. Usually cuttings are taken at the time of pruning from October - January.

 

3. Stenting It is the advanced and quickest method of rose propagation. In this method budding is done on cuttings (local unrooted rootstock) and kept in IBA (500 ppm) for 15-20 minutes. After that these budded cuttings are planted for rooting in mist chamber. Rooting and bud union takes place simultaneously which saves the time.

 

Climate: The ideal temperature range for rose cultivation is 15 to 27ºC. Most commercial rose cultivars are best grown at 15.5ºC night temperature. Lower temperature, around 15 to 16º C improves flower quality and high day temperature, about 27º C, reduces stem length. The ideal humidity range for the rose is around 60% to 65% (RH). The micro jet irrigation system and misting systems in the polyhouses helps to control the humidity level.

Soil: For successful cultivation, soil should be well drained, having porous structure and slightly acidic reaction. Soils with slightly high humus (organic matter) content are preferred.During raised bed preparation, first of all the good garden soil should be sterilised with chemicals or solar sterilization is done. The soil is thoroughly mixed with well decomposed farmyard manure along with basal fertilisers. Moisten it with water in sufficient amount. It is necessary that the soil is loose and humid but not too wet or muddy. In polyhouses, sometimes the bed consists of earthen/plastic pots. On an iron stand, the pots are arranged at specific distances, forming beds.

Planting: Budded plants are the starting material for rose cultivation. According to variety and growth habit, rose plants are planted on raised beds in double lines accommodating 6-7 plants/m2.  Place the plants in position, at the required distance, with the roots straight down (no bent roots) and refill the furrows with the loose soil that came out of the furrows and press tightly. Avoid drying of the roots. The depth of the plant should be such that the budded part is placed at the soil level, or at a maximum of one cm above, after refilling the furrows. It is important that roots are covered in the soil. Holes can cause the root to dry up and die. Under fully automated/temperature and humidity control polyhouses , roses can be planted any time of the year. However for naturally ventilated polyhouses the planting time is as under:  Low hills:  October to November, Mid hills   :  October-November, February-March and High hills:  March-April

Irrigation/ Watering the plants: After planting, the plants have to be watered immediately. In the first week, watering has to be done with sprinklers or with a hose pipe. This has to be done as many times as needed so that the surface does not become dry. During the first two months, the plants have to be watered frequently, because they do not have much roots. After about two months, where there are enough roots, irrigation can be slowly changed to the normal irrigation rate. Usually drip system of irrigation is preferred because of more economization of water and less build up of relative humidity and the resulting disease outbreak

 Building of Young Plants/ Bending:

First Growth: Soon after planting two to three eyes per branch will sprout. They will grow until flowering in five to six weeks. These shoots must not be cut or bent, but left upright. When most of the buds show colour, knock off the buds.

Second Growth: After knocking the buds, the second growth will come to flower after four to five weeks. By then, the vegetation will be 50 to 60 cm high, wait until the maximum of the branches are showing big buds, nearly colouring.

Bending/Green Bending: Bending is necessary for keeping enough leaves on the plants and the leaves are important for the production of sugars. From a plant, a minimum of four stems, either flowers or blind shoots, must be bent. When bending, it is important to take off the buds. The place where to bend is as close to the one bush as possible (maximum 5 cm), without breaking the branches. To avoid breaking, it is advised to do the bending in the afternoon and to create two 45 degree bends rather than one 90 degree. The bending should be such that the tops of the stems are below the horizontal. It is important for the apical dominance of the plant.

Pruning and Flower Regulation: Roses can tolerate hard pruning also. Pruning is the practice followed for obtaining flowers as per our requirement. Pruning when done during the third or fourth week of October to produce rose flowers for the Christmas season. The same operation produces the second flush of flowers in February for Valentine’s Day. Most of the commercial cultivars take about five- and a- half to six weeks from pruning to produce flowers during summer and about eight weeks during winter. Removal of dead, dry branches and maintenance of plant architecture is also an important aspect of pruning.

Disbudding and de-shooting: It is the practice of removing undesirable buds. For most spray type varieties, the center crown bud is to be removed and in hybrid Tea roses only one or at best two buds should be allowed to flower upon each shoot so as to have a large size bloom. Simultaneously, the soft shoots arising from the leaf axils should be removed from time to time.

Weeding:  It is the removal of undesirable plants from the field and can be controlled manually, mechanically or chemically. Organic and plastic mulches are used to maintain the moisture content and restrict the growth of weeds in the field

Stage of Flower Harvesting :

•             For local market : When outer one/two petals start unfurling.

•             For distant market : Fully coloured tight buds.

  White, pink and yellow cultivars are harvested earlier to red as red may not open if harvested  at  tight bud stage.

 Harvesting of cut stems starts 38 to 42 days from pruning during summer and upto 55 to 60 days in winter depending upon the variety. The stage of harvesting depends upon the cultivar and distance to the market. Yellow coloured types are generally harvested at the tight bud stage for export. Harvesting should be done early morning or late evening, so that less preconditioning/precooling is required. Immediately after harvest, the cut flowers should be kept in a preservative (8HQC) solution at 2º C for about three to five hours. Water used for making treatment solution should have an acidic pH (below 6.8).Harvesting should be done on the five leaves from the bottom, on the stem of the first new growth. Roses should be harvested at the tight bud stage. Roses cut too early may also contain very little carbohydrates and may not open. Besides, due to insufficient hardening of the neck region, the peduncle may not be able to support the weight of the bud, which droops in the neck region. This is referred to as ‘bent neck’. The stage of harvest also varies greatly with the variety, distance to the market place, prevailing temperatures and consumers satisfaction. Stems should be cut leaving at least two 5- leaflet leaves on the stem.

Especially, some varieties like ‘First Red’ which have long thorns and hence should be handled with extra care, otherwise the thorns may damage the leaves and petals on the other stems and spoil the quality of the blooms. After harvesting, the stems should be put in buckets containing water.

Qualities of Cut Stems:

• Long stemmed varieties are graded from 40 cm onwards with a difference of 10cm, whereas short- stemmed varieties are graded from 40 cm-65 cm with a difference of 5 cm.

• Leaves should be dark green and healthy. There should not be any yellowing due to micronutrient deficiency. Leaves should also be free from dust, chemical residue, chemical injury, spider mites or powdery mildew, etc

•The flowers should not be bullhead, to open, too light, with bent neck, damaged by thrips or botrytis, etc.Bud size should be representative to the variety.

Grading:

•The cut stems are graded according to stem length. The flowers with cut stem length 60-90 cm and above are graded as ‘A’, whereas flowers with shorter stem length are kept in a category  Grade ‘B’. Flower yield: 250 flowers/m2/annum

Packaging and Transport of Flowers: The graded stems are made into bundles of 20 each and tied loosely with rubber bands. The buds should be wrapped with 2-plysoft corrugated paper and tied loosely with a rubber band to secure the buds in position. The wrapping paper should project at least 2-3 cm above the bunch to protect the buds from thorns or from coming in contact with box.The leaves from the lower 4-5 cm portion of the stems are removed and stems put in buckets containing chlorine (50 ppm), aluminium sulphate or citric acid (300 ppm). The bunches are packed in pre-cooled 5-ply teleboxes of fibreboard. The flowers are transported to the nearest markets in refrigerated vans.

Diseases and Pests:

1. Die- Back (Diplodia rosarum)

As the name indicates, the disease causes death of the plant from top to downwards. It is generally observed after pruning. Blackening of twigs below the pruned surface occurs, which at times extends further down, killing the whole plant.

Control: Pruning cut should be slanting. The pruned cut is to be applied with fungicidal paste.

2. Powdery Mildew (Sphaerotheca pannosa var. Rosae)

The fungus appears whenever the days are warm and nights are cool. Almost all the aerial parts of the plants are generally affected and one finds white powdery growth of the fungus particularly on the lower side of the leaves. Flower buds when affected fail to open and are damaged.

Control: Proper hygiene should be maintained. All fallen leaves and other plant debris should be removed and destroyed.

3. Black Spot (Diplocarpon rosae)

This is a fungal disease which causes serious problem in dull cold climate of the temperate region. The disease is characterized by dark brown, circular spots with fringe borders, present on both sides of leaflets. Since the black spot fungus is located under the protecting cuticle, no fungicide can kill it without destroying the leaf.

Control: All fallen leaves and other plant debris should be removed and destroyed.

4. Rust (Phragmidium spp.)

Rose rust is considered as a serious disease of rose and is most common in warm and humid areas. The disease is characterised by the presence of reddish- orange pustules on leaflets and sometimes on petioles.

Control: All fallen leaves and other plant debris should be removed and destroyed.

5. Grey Mould (Botrytis cinerea)

This disease prevents the blooms to open. Buds turn brown and decay, individual petals turn brown and shrived. Infected parts may become covered with grey to greyish brown mycelium which often sporulates profusely.

Control: All fallen leaves and other plant debris should be removed and destroyed.

 PESTS:

1. Aphids: Flowers when attacked become malformed. The aphids can be easily controlled by spraying Malathion (0.1%) or metasystox (o.1 to 0.2%) or rogor (0.1 to 0.2%).

2. Thrips: Thrips are very minute, long and slender insects which inhabit the under surface of tender leaves and suck sap from leaves and flower buds. The chemicals used for aphid control are also effective in controlling thrips.

3. Red Spider Mite: These are minute, polyphagous pests found in large colonies on the underside of leaves covered with fine silky webs. As a result of their feeding, white specks appear on the leaves and these specks coalesce and appear as white patches. Ultimately, affected leaves become mottled turn yellow and fall. The damage is more pronounced during warm and dry season. Frequent spray with sulphur helps to control this mite.

4. Red Scales: A number of scale insects infest roses in the greenhouse and in the garden. Each scale represents an individual insect which sucks out the plant sap. The tiny insects occur in thousands and the affected branches become dry. The menace can be removed by rubbing the scurfy encrustations with a used tooth brush or a cotton swab dipped in methylated spirit.

 Physiological Disorders

 (1) Blind Shoots

The normal flowering shoot on a greenhouse rose possesses fully expanded sepals, petals, and reproductive parts. The failure to develop a flower on the apical end of the stem is a common occurrence. Such shoots are termed as blind shoots. The sepals and petals are present, but the reproductive parts are absent or aborted. Blind shoots is generally short and thin, but it may attain considerable length and thickness when it develops at the top of the plant. This may be caused by low temperature, insufficient light, chemical residues, insect, pests, fungal diseases and other factors.

 (ii) Bull Heads or Malformed Flowers

The center petals of the bud remain only partly developed and the bud appears flat. They are common on very vigorous shoots, particularly bottom breaks, and it is possible that there is a lack of carbohydrates to develop the petals. The cause of bull heading is yet unknown, however, thrips infestation will also cause malformed flowers. Also at low temperature, some varieties will form bull heads.

(iii) Bent Neck

 Premature harvesting is the core problem of bent-neck in roses. The stem right under the bud not strong enough to carry the weight of the growing bud/flower. When the stem bends in this way, the vascular bundles are pinched shut and the flower's water supply is cut off. The leaves me other hand, remain healthy. Premature harvesting also makes the tissue more sensitive to lack of water. If loss of moisture due to evaporation is insufficiently compensated for by water absorption the stem will bend at the most vulnerable/softest and least woody point, especially when Vascular blockage also plays a role. The degree of susceptibility to bent-neck varies among cultivars. Excessive artificial lengthening of daylight hours in the greenhouse, during winter months, can cause the stomata to lose their ability to close. Evaporation will then continue at a rapid pace, particularly at high temperatures in the stores and at the home of the customer.

 

Prevention

• Harvest the roses at the appropriate level of maturity.

• Cut at least 5 cm off the stem to remove blockages.

• Use post-harvest products such as 8 HQC, AVG, Chrysal, Flora life, Oasis during transport

and retail phase

 (iv) Colour Fading

The off-coloured flowers are seem to be a problem with some yellow varieties. In these varieties the petals may be green or a dirty white instead of a clear yellow. Raising the night temperature several degrees will reduce the number of off-coloured flowers. Occasionally the pink or red varieties develop bluish-coloured flowers. This is very often associated with use of organic phosphate and various other kinds of insecticides.

(v) Limp Necks

The area of the stem just below the flower “wilts” and will not support the head. This may be due to insufficient water absorption; cutting off the lower 1 to 2 inches of stem and placing the cut stem in water at 37°C will revive the flower.

(vi) Blackening of Fose Petals

This is caused by low temperature and high anthocyanin content. GA, treatment causes accumulation of anthocyanin in petals of Baccara roses. This effect was more pronounced at low temperature (20°C at day and 4°C at night) than in higher temperature (30°C at day and 20°C at night).