Tuberose: Harvesting and Diseases | Flowers

After reading this article you will learn about:- 1. Harvesting, Packing and Marketing of Tuberose 2. Method of Extraction of Tuberose3. Important Insects, Pests and Diseases 4. Diseases.

It is commonly called as Rajni Gandha (Hindi, Bengali), Gul-e-chari, Gul-e-Shabab (Urdu), Nishigandha (Marathi), Nishi Gandhi (Malayalam) and Sempangi (Tamil) and scientifically—Polianthes tuberosa and belongs to family Amrylladaceae.

Tuberose has long, narrow, light green leaves. Plant grows about 25-30 cm tall. The flowering stalk is 75-100 cm long having 25-50 florets spike. It produces, waxy, white, highly fragrant single semi double or double flowers on a long spike which open from base to the top.

Single variety has been named after the place of growing as Mexican single, Calcutta single, Hyderabad single, Coimbatore single, Bangalore single, etc. Tuberose blooms during summer, rainy season and autumn. Thus, it becomes very important cut flower of summer and rainy season of India. Its flowers are also used as cut, loose flower for making garlands, bracelets or for hair do.

Single white flowers are highly fragrant and hence, are used to extract its valuable essential oil which is sold on premium. Its essential oil is rich in geraniol, nerol, benzyl alcohol, eugenol, benzyl benzoate and methyl anthranilate.

Due to this compound, flowers emit a delightful fragrance and are source of tuberose essential oil. These compounds are present in oil glands which are deep seated in petal and hence, solvents like hexane are used to extract the oil.

White flowers of tuberose can be coloured by dissolving coloured dye in vase water like Bromocresol green and Bromophenol blue which will impart different shades of blue colour. Phenol red imparts yellow colour and erythrosine red will impart rose colour to flowers. Different shades and intensity of colour will depend upon the concentration and quantity of chemical used.

Origin:

It is native of Mexico from where it reached to different parts of world during 16th century when Spanish conquered it. At first it reached Europe than to Africa and Asia. Its arrival to India is not well documented but Britishers might have introduced it. Now, it is a commercial crop of France, Spain, Morocco, South Africa, Israel, New Zealand, U.S.A., tropical and sub-tropical areas of India and Ceylon.

Area and production:

Tuberose is well adopted and grown commercially in various parts of India. It is prominently grown in West Bengal—Bargan, Golaghat, Midnapur, Panskura, Ranaghat, Thakur Nagar; Karnataka—Mysore, Bangalore; Andhra Pradesh —East Godavari, Guntur, Chitoor, Nellore, Visakhapatnam, Krishna districts; Tamil Nadu—Coimbatore, Madurai; Uttar Pradesh—Meerut, Saharanpur, Muzaffarnagar; and in limited areas of Haryana and Punjab. In all total area under tuberose in India is estimated to be about 12,000 ha.

Species and Cultivars:

Polianthes is a monotypic genus and is closely related to Bravoa. There are about a dozen of species of Polyanthes but they are not clearly distinct. The only close relative of P. tuberosa is considered to be Polyanthes gracilis. Other species are P. palustris, P. durangensis, P. longiflora, P. platyphyla, P. graminofolia, P. geminiflora, P. blessii, P. pringlei, P. sessiliflora, and P. nelsonie, etc.

The haploid number of chromosome of tuberose is 30 of which 5 are large and remaining 25 are small. Seed setting in tuberose is quite erratic in single flowered cultivar whereas it is not observed in the double type.

The variegated cultivars, however, exhibit high degree of seed setting. The exact reasons of poor seed setting are not known. It is not due to any defects in the formation of the pollen grains or development of the embryo sac. It might be due to lack of pollinizers because flower are not colourful and attractive.

Cultivars:

There are four type of varieties viz. Single—it contains one row of petal; semi double—it contains two to three rows of petals; double having more than three row of petals; and variegated—in these leaf margins are variegated which there highly suitable for landscape planting.

1. Single Flowered:

The cultivars have single row of petals. Floral buds are greenish white whereas flowers are waxy white. Loose flowers are used for decorations and floral arrangements. Flowers are highly fragrant and, hence, are used for extraction of essential oil which is present at about 0.08-0.11%. Seed setting is observed. Single types are identified with the name of locality like Mexican, Calcutta, Pune, Hyderabad, Coimbatore, and Bengaluru.

2. Rajat Rekha:

It has been developed through mutation breeding at NBRI, Lucknow. Leaves are variegated with slivery white streak along the middle of leaf blade. Flowers are single and oil content is about 0.089%. In garden, it is planted for its variegated leaves and flowers.

3. Shingar:

This variety has been developed from a cross between single × double. The flower bud is slightly pinkish tinged. Florets are bigger than Calcutta single. The average yield of loose flowers is about 15 tonnes/ha which is 40% higher than Calcutta single. It is considered resistant to Meloidogyne incognita nematode. Therefore, it is being preferred by growers.

4. Prajwal:

It is also a hybrid between single × double. Its spikes are tall and stiff. Flower buds are slightly pinkish in colour but flower are waxy white. The individual flowers are large and yield is about 12 tonnes/ha. It is grown for loose flower as well as for cut flower purpose.

5. Semi-double flowered tuberose:

In these type flower petals are in 2-3 rows. Flowers are white.

6. Vaibhav:

This is a cross between Mexican single × IIHR-2. The flower buds are greenish in colour. Flowers are white. Spike yield is comparatively higher. It is recommended for cut flower production.

7. Double flowered tuberose:

As the name indicates, flowers have more than three rows of petals on long and sturdy spikes. Flowers open slowly. Therefore, it is highly suitable as cut flower. It has pinkish tinge at the top of flower buds, flower colour in white. The ‘Pearl’ variety does not open well.

8. Swarna Rekha:

It is a mutant of double type developed at NBRI, Lucknow through gamma radiation. Leaf margins are golden colour. Flower buds are pink but flowers are white and double.

9. Suvasini:

It has been developed by crossing between single × double. Flowers are double, white, bold and spikes are longer. Highly suitable for cut flower production. It yields about 25% more than the Pearl.

Climate:

Tuberose is a half hardy bulbous crop and happily grows in mild climate. It can tolerate wide range of climatic conditions and areas having a range of 20-35°C temperature are considered good for its successful growing. For its luxuriant growth and high productivity the mild temperature of about 30°C with high humidity is most ideal.

The temperature above than 40°C reduces the productively and quality of spikes. Much lower temperature i.e. 1-2°C with ground frosts kill the vegetative parts of the crop completely. However, sprouting and flowering is normal in ratoon crop with the onset of spring.

Soil:

Tuberose is a bulbous plant; hence, loamy and sandy loam soils having pH of 6.5 to 7.5 with good aeration and drainage are highly pertinent for its successful cultivation. It has been observed that it can tolerate higher degree of pH i.e. up to 8.2 to 8.3. Its cultivation can be extended in marginal and unproductive soils affected by salinity and alkalinity. The soil should be rich in organic matter and good water holding capacity for proper growth of tuberose.

Preparation of field:

The field should be well prepared by giving 2-3 ploughings and incorporating 40-50 tonnes/ha of well rotten farm yard manure before planting. The application of 100 kg N and 400 kg P₂O₅ and 200 kg K₂O/ha is found to be optimum which should be applied before planting the crop along with 8 kg of thimet or 2.5 kg carbofuron/ha should be mixed to protect the crop of tuberose against nematode.

Planting time:

Tuberose is generally planted in February-March (East India) and March-April (North India). In the hills it is planted in April-May. In South India, the crop is planted in July-August. Under Bengaluru conditions, the planting can be done round the year but April-May planting is good for better crop.

Bulb selection and planting:

The size of bulb, its diameter and weight reflects the storage of food material which will be utilized for the growth, flower production and subsequent production of new bulbs. In tuberose, the production of daughter bulbs and flower production go simultaneously and hence, sufficiently good sized bulbs should be used for planting the crop. On an average the bulb size of 2-3 cm is good for raising healthy crop. But relatively larger bulb i.e. 3.1-3.5 cm weighing about 40-50 g exhibit better result and produced good quality spikes.

After field preparation, the field is divided into plots leaving the path and water channels. Bulbs are planted in the field at the distance of 20 × 20 cm and at 4-5 cm deep. Little more wider distance of 30 × 30 cm is followed in Maharashtra. Close planting at the distance of 15 x 15 cm has been found satisfactory at many locations including Assam. After planting field is irrigated lightly.

Manuring:

Tuberose is heavy feeder and very exhaustive crop and thus responds well to the applied organic and inorganic nutrients. Fertilizer application of 200, 400 and 200 kg N, P₂O₅ and K₂O per ha, respectively is recommended for quality flower production and bulb production.

Half of N and full dose P and K to be applied before planting and remaining half dose of N to applied one month after planting. This can be increased or decreased depending upon fertility of soil. From Assam, it has been reported that the application of 80-40-60 g/m² of N, P₂O₅ and K₂O in plant crop and ratoon crop was found highly beneficial in terms of flower production and bulb production of single variety of tuberose.

Irrigation:

Tuberose requires sufficient moisture for its growth and quality flower production. It is advised that a light irrigation should be given before planting which helps in early sprouting and growth of plant. Too much moisture at the time of sprouting of bulb result into rotting of bulbs. Similar conditions during flowering affect the quality of spikes adversely.

The frequency of irrigation depends upon soil types, weather conditions and stage of growth. In general weekly irrigation is required during April-June. Irrigation interval during July-September depends upon rains and their intensities whereas during October to March irrigation at the interval of 10 days keeping the rains in view is deficient to meet its requirement.

Weeding:

It is advised to keep the tuberose field free from weed otherwise they compete for nutrient and moisture with the main crop. Since the tuberose is in the field for full 1-3 years and different kind of weeds appear season wise.

Hand weeding is laborious, time consuming and expensive. Generally after each irrigation, weeding is done. Hoeing is also done to loose soil and destroys the weeds. Pre-planting application of atrazine @ 3.0 kg/ha-has been found effective in controlling weeds in tuberose.

Harvesting, Packing and Marketing of Tuberose:

Depending upon the purpose and the use of tuberose flowers, harvesting is done accordingly. For loose flowers, individual flower is plucked regularly which are used for various purposes whereas for cut flower the spike is cut from the base so that longer spike is available. These operations are done in cool hours either early in the morning or in the evening keeping the harvest of spike taken for the travel of these spikes.

Similarly the stage of harvest of spike is decided upon distance of travel. For local market and immediate purpose spikes are harvested when two-three rows of basal flowers are open. For distant market, spikes are harvested when basal flower just going to open. Loose flowers are generally packed in bamboo baskets, holding about 10-15 kg flowers and are sent to the market. These are sold by weight.

The quality of cut spikes are judge according to the length of spikes, length of flowering zone, number of florets, quality of florets. These cut spike are bunched in round bundles of 100 spikes. Basal portion of the spikes wrapped with newspaper. To avoid any injury to flowers and buds, the whole bundles is wrapped in soft, white tissue paper or perforate polythene of 300 gauges.

A holding solution of 2% sucrose + 300 ppm aluminum sulphate was found best for the post-harvest life and quality of cut spikes of tuberose cv Shringar. Another useful combination is 1% sucrose + 300 ppm citric acid + 50 ppm calcium nitrate at 4°C for 48-72 hours to improve the vase life of spikes. These spikes can be stored at 4°-7° for 5-7 days.

Lifting and curing of bulbs:

At the time of complete maturity growth ceases completely, leaves become yellow and dry out. At this stage irrigation is withheld and after two weeks, clumps of bulbs are dug out from the ground. The bulbs are separated out and grouped according to their size. Cleaned and graded bulbs are stored on shelves for curing.

The position of these bulbs is changed after two weeks to prevent fungal attack and rotting. Then bulbs are stored in cool and shady place at about 18°C for four weeks before planting which result in production of good quality of bulb and flower spikes of subsequent crop. Longer storage at 30°C or above before planting advances flowering but quality of spikes and bulbs deteriorates.

Flower and concrete yield:

Flower production depend upon climatic conditions, soil type, its fertility level and agronomic practices followed, etc. and hence, different level of production has been reported from various parts of India. Under optimum conditions single tuberose yields about 5,00,000 flower spikes/ha or 10.5 tonnes/ha of loose flower. In a cycle of three years, first two years flower yield is high and in third year it is comparatively lower. In one year about 9.2 to 10 kg concrete/ha can be obtained and in turn 1.75 kg of tuberose absolute can be obtained.

Method of Extraction of Tuberose:

The simple method of steam distillation for extracting the volatile oil of tuberose cannot be adopted as tuberose do not yield the essential oil on steam distillation. Hence, the solvent extraction method is employed. Freshly plucked fully opened flowers in cool hours of the day (before 8.00 a.m.) are used.

The purified hexane is a colourless liquid with a boiling point of 60-80°C. The flowers are immersed in purified hexane for 30 minutes. The complete extraction of the perfume from the flower can be ensured by slowly rotating the extractor having flowers and solvent for about 20 minutes. After the complete extraction of the perfume from the flowers, the solvent is filtered and concentrated at a constant temperature at 70°C.

At this temperature solvent evaporates and condensed for reuse, leaving the perfume and other plant waxes. To purify further the remaining vapours of solvent containing perfume, wax and pigments is distilled in a vacuum distillation unit where the complete removal of solvent takes place, leaving floral concrete.

In any unit, four components are there:

(1) Extractor,

(2) Evaporator,

(3) Condenser and

(4) Vacuum distillation.

Important Insects, Pests and Diseases of Tuberose:

Aphids:

These are very small size insects feed on flower buds and on growing tips. These can be controlled by spraying 0.1 per cent spray Malathion or Rogor.

Thrips:

These feed on leaves, flowers stalks and flowers and suck the sap and ultimately damage the crop. These can be controlled by spraying 400 ml of Rogor. 30 EC (dimethoate) in 80-100 L of water per area when the attack starts and repeat after 15 days if necessary.

Red spider mites:

Yellow stripes and streaks appear on the foliage due to attack of mites. Spraying with endrin 9 kg of 10% wp/100 gal of water has been effective in controlling mites.

Root knot nematode:

It is caused by Meloidygyne incognita, and has been observed that root knot nematodes reduce crop yield considerably and make the plants highly susceptible to the attack of Fusarium oxysporium sp. dianthi. Various methods like crop rotation, treatment of bulb before planting (dip. bulbs in 0.5% nuvacron 40 E.C. for half an hour) or treatment of soil with Basamid @ 40 g/m² or addition of neem leaves in the soil is recommended.

Recently it has been reported from IIHR, Bangalore that neem based formulation of Pochonia chlamydosporia, (verticillium chalamydosporium) (40 g @ 10⁶ CFU/g) and Trichoderma harzianum (40 g @ 10⁶ CFU/g) per 2 × 2 m sized plots before planting and subsequently once in 4 months decreased the incidence of root knot nematode and wilt disease complex significantly. These treatments increased the number of flotes per spike and spikes/plot, significantly.

Application of 8 kg thimet or neem cake @ 1 tonne/ha controls nematode infestation. Besides, the use of nematode free planting material and hot water treatment of bulbs at 57-58°C for 30 minutes is recommended. Further, the population of nematode in the field can be kept under check when intercropping with marigold is followed.

Diseases of Tuberose:

Botrytis spots or leaf blight:

This disease is caused by Botrytis elliptica and causes serious damage to the leaves. It can be controlled by spraying 0.2% Blitox.

Alternaria leaf spot:

It is caused by Alternaria polyanthii. Faint concentric rings appear on mid rib of leaves but rarely near the margin of leaves. The leaves become necrotic and dry up with the infection. It can be controlled by spraying plants with 0.2% of Dithane M-45.

Stem rot sclerotial wilt (Sclerotium rolfsii):

Main symptoms are the appearance of spots of green and brown round spots on the leave and leaves become yellow and ultimately dry up. The fungus ultimately attacks the roots and infection gradually spreads to bulb and collar portion of the stem which causes rotting. Drenching soil with brassicol (0.1%) or thiram (0.2) or Bavistin (0.5-1%) is effective in controlling the disease. If necessary, repeat at the interval of 20 days till it controls.