In India, tuberoses are cultivated for the production of flower spikes and loose flowers on a commercial scale for the domestic market. The flowering of tuberose starts 3 to 3 1/2 months (80 to 100 days) after planting and flowering time is July onwards. August-September is the peak period of flowering. Tuberose flowers all the year round. Depending on the purpose, harvesting is done by cutting the spikes from the base or single flowers are harvested as they open day by day.
For marketing of cut flower spikes, the tuberose is harvested by cutting the spikes from the base when 1-2 pairs of flowers open on the spike. Spikes are harvested at budburst stage preferably in the morning before sunrise or late in the evening by clipping with a sharp knife or secateurs that gives a clean cut. About 4-6 cm basal portion of the scape has to be left to allow the growth of bulb. For loose flower purpose individual flowers which grow at the horizontal position on flowers stalk are plucked early in the morning by 8.00 a.m.’
After harvesting the main crop, the flower stalks are headed back (cut to the base) and the plots should be well- manured and irrigated. About 3-4 ratoon crops can be taken from a single planting. For the proper growth and development of plants, fertilizer dose as given in the main crop should be applied in two equal split doses in January-February and April. All other cultural practices should be done as in case of main crop. There is early flowering in ratoon crop as compared to main crop. The ratoon crop results in more number of spikes but reduces number of florets, length of spikes and weight of flowers.
Therefore, ratoon crop should be used only for loose flowers or oil extraction purpose. In temperate climate, during November – December, when temperature drops, leaves of the plants turn yellow and die and plants undergo dormancy. Digging of bulbs should be done at this stage. With the increase in temperature the crop regains growth from the previously planted bulbs which is termed as ratooning. For ratooning in tuberose, the yellowing plants should be twisted from the ground level which leads to early maturing of bulbs.
Lifting, Curing, and Storage of Bulbs
Harvesting stage of tuberose bulb is important for storage of bulbs and their growth. The bulbs are harvested when the flowering is over and plant ceases to grow. Bulbs reach maturity at about 40-50 days after flowering and at this stage, the leaves become yellow and dry. At this stage, irrigation is withheld and the out the bulbs. The leaves are cut off at the ground level and the bulbs are dug out. After digging, the bulbs are lifted out and adhering earth shaken off neatly and thoroughly. The offsets or bulblets are then separated out by hand, which are used as seedstock for the next season. The bulbs are then graded based on the size into mature (> 1.5 cm diameter) and immature (< 1.5 cm diameter).
Cleaned and graded bulbs are placed on shelves to dry or cure. To hasten curing, artificial heat of 27o to 35o nC may be applied. The bulbs must be stirred or have their position changed every few days to prevent fungal attack and rotting. Curing can also be done by tying the bulbs in bunches and hanging them on frames and walls. The bulbs are also treated with 0.2 per cent Bavistin or mancozeb powder to prevent their rotting. An ambient air temperature of at least 18oC for four to six weeks or exactly six weeks at 30oC stimulates the yield of commercial sized bulbs. Longer storage at 30oC advances flower spike yield but the quality of spike deteriorates and the bulb number decreases.
Flower production varies with cultivar or variety and depends upon bulb size at planting time, density of planting, cultural practices adopted and climatic condition prevailing in the area. Flowers are ready for harvest in about 3 to 31/2 months after planting. One hectare of tuberose plantation yields 4 – 5 lakhs of spikes per year for cut flower purpose. In case of single varieties, 14-15 tonnes / ha of loose flowers may be harvested. In addition, 20-25 tonnes / ha of bulbs and bulblets may be harvested at the end of 3rd year.Crop duration: 2 ½ to 3 years.
Post Harvest Management
Immediately after harvest, the lower portion of the cut spikes should be immersed in water for prolonging the vase life of spikes. The spikes are made ready by removing the unwanted leaves to minimise the transpiration loss for sending to floral markets. Further, pulsing of spikes at low temperature (100C), for about four hours with the ends immersed in water, is helpful in prolonging life of spikes to be sent to distant markets.
A holding solution consisting of sucrose 2 % + Al2 (SO4)3 300 ppm is best for increasing the post harvest life and quality of cut spikes of tuberose.
Grading and handling
The flower spikes for cut flower purpose are graded according to the following quality attributes viz.,
• Spike length
• Length of rachis
• Number of flowers per spike
• Weight of spikes and
• Quality of individual florets.
The straight and strong stem of uniform length and uniform stage of development are preferred. Flowers should be free from bruises and diseases and pests. The individual florets for loose flower purpose are graded according to their size.
The fresh flowers can be stored at 10oC for 5 days.
- Central Coastal Agricultural Research Institute, Ela, Old Goa, Goa