Cut flower quality and longevity are influenced by pre and post harvest practices. Nearly 20-40% of the cut flowers produced are lost due to faulty harvesting, post harvest handling, storage, transportation and marketing. These losses can be reduced by careful harvesting, post harvest handling, temperature management, sanitation and judicious use of floral preservatives.
Maturity of the cut flower mainly decides its post harvest life. The flowers must reach certain stage of development before harvesting. Most of the cut flowers are harvested in the early morning or late in the afternoon. Flowers are harvested with sharp knife or secature.
Harvesting is done at the tight bud stage when the colour is fully developed and the petals have not yet started unfolding.
The spikes are cut in tight bud stage when colour has fully developed in the mature unopened buds leaving 4 leaves on the plant.
Standard carnation flowers are harvested when the outer petals unfold nearly perpendicular to the stem. Spray types are harvested when two flowers open and the remaining buds show colour.
Standard flowers are cut soon after the disappearance of green colour in the centre of the flowers and the center petals are fully expanded. Pompons are cut when they are fully developed. Spray types should be cut when the central flower is open and the surrounding flowers are well developed and the varieties which shed pollen badly will have to be cut before they become unsighty. Cutting the stem while the flowers are slightly on the “green” side is preferred because it offers a better quality product for the customer. The stems are harvested by pulling them out and breaking of the root system leaving it behind in the bed/field be ploughed into the soil when bed/field is prepared for next crop.
Flowers are harvested when they are fully open as the flowers cut prior to their maturity will wilt before reaching the wholesaler.
Flowers are harvested when the spathe completely unfurls and the spadix is well developed. Harvesting the blooms, when one third of the flowers on the spadix mature, change of colour can be observed that moves from base to tip of spadix. At this stage the flowers are harvested. Harvesting has to be done during cooler parts of the day i.e.) early morning or late evening In general the cut blooms are placed in water held in plastic buckets immediately after cutting from the plant. Delay in keeping in water allows air entry into the stem and causes blockage of the vascular vessels. Cut flowers after harvest should be shifted to pre cooling chambers in refrigerated vehicles having 2-4°C temperature as they deteriorate most rapidly at high temperature. After reaching the cooling chamber, another cut is given above the previous cut in roses, whereas in orchids lower 0.75 cm of the peduncle is cut. In gladioli, 2.5 cm diagonal cut is made to expose maximum capillary tissues for absorbing more water.
Pre cooling removes field heat rapidly from the freshly harvested cut flowers. Precooling lowers respiration rate, water loss and ethylene synthesis. Most of the time, greatest loss occurs due to delay in precooling. Generally two methods of cooling are followed. The first one is room cooling and the other one is forced air-cooling. In room cooling, the flowers are held in buckets which are placed in a cooler. In the forced air cooling system, the flowers packed in perforated boxes are subjected to cool air blasts for a specific period in a closed room to remove field heat. The flowers take 20-30 minutes for cooling in forced cooling depending on the flower type and initial temperature in the box. Proper temperature (1.7°C to 4°C) and relative humidity (90-95%) maintenance are critical to the success of precooling, otherwise the flowers will dessicate.
Postharvest handling practices for important cut flowers
Roses must be placed in a bucket of water inside the polyhouse immediately after harvesting and transported to cold storage (2-4°C). The length of time depends upon the variety and quality of the roses.The flowers are graded according to the length. It varies from 40-70 cm depending on the variety and packed in 10/12 per bunch
After harvest, the flower stems have to be trimmed at the base and should be immediately placed in a bucket of preservative solution of warm and deionized water. A good preservative solution for carnations should be acidic (pH 4.5) with 2-5% sucrose and a biocide not phytotoxic to carnations. After keeping in preservative solution for 2 to 4 hours, flowers should be placed in a refrigerated room at 0-2°C for 12-24 hours. The flowers can be stored for two to four weeks before marketing. For this, the flowers have to be packed in cartons lined with polyethylene film. These cartons should have sufficient vent holes. The full cartons should be pre-cooled with out lid. The plastic is then loosely folded on top of the stems and the lid is closed. These cartons are stored in cool chambers designed to maintained 0°C with good air circulation and a constant relative humidity of 90-95%.
After harvest, the stem have to be cut at equal length (90 cm is the standard), bunched in five putting a rubber band at the base and sliding them into a plastic sleeve and putting the bunches in plastic buckets filled with water. Early morning on the day of shipment (or night before) the bunches can be packed in boxes.
Harvesting is done when outer 2-3 rows of disc florets are perpendicular to the stalk. The heel for the stalk should be cut about 2-3 cm above the base and kept in fresh chlorinated water.
Since most orchid flowers are long-lived on the plants, they should not be harvested until needed. If these are to be cut they should be stored at 5-7°C. At this temperature most orchid flowers can be stored for 10 to 14 days. Plastic film storage is attractive and can be utilized.
Packaging is another important aspect in the flower trade. An ideal package should be airtight, water proof, strong enough to withstand handling and small in volume. Many ways are followed to pack orchid flowers. Cymbidium spikes are often packed 100 flowers to a box. Standard florist boxes are used for the packing of Cattleya floors. HawaiinDendrobium is packed in 4 dozen sprays per box. Keeping of a wet cotton at the cut end of the flower stem which is wrapped with a polythene wrapper helps to maintain humidity.
Immediately after arrival, the lower 0.75 cm of the peduncle is cut off, and the flower is inserted into a fresh tube of water containing preservative. In case of spray type of orchids, the basal 2.5cm of the stem is cut upon arrival, placed in warm water at 38°C with a preservative and hardened off at 5°C. Foliar application of aluminium chloride at 500ppm, ammonium molybdate at 100 ppm or boric acid at 1000ppm increased the vase-life of Oncidium.. Hydroxyquinoline resulted in additional bloom opening of the flowers and also increased the vase-life.
Flowers can be easily stored at 13°C for 2-3 weeks. The flowers, which are harvested when 3/4th of the length of the spadix colour changes, lasts longer than the other flowers which are harvested either early or late. The average vase life depends upon life of flowers range between 12-24 days depending upon the cultivars. Anthurium is packed in cartons lined with impervious polyethylene sheeting of adequate length and width so that, when packed, the sheet can be folded over to prevent the moisture of the dampened flowers and packing material from dampening the box itself. Newspaper is used to line the carton, and shredded newspaper is used to cushion spathes that are arranged in rows facing opposite directions. Each individual spathe is wrapped and tucked with un-printed newspaper or other white paper.