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Harvesting and Post-harvest handling of flowers

By NDIRITU NJORA and ANTHONY MUTAI

According to industry experts, it takes about 10 years of sweat to deliver a flower to the market. From breeding to trials to commercialization then consumer acceptability a journey through which out of thousands of  the initial seed, only one might cross the tape to deliver a two to three-week vase life of beauty. It is those last weeks that matter most. Between harvesting the flower and purchase by the end consumer, one mis step can boomerang on the 10-year investment.

Where does the last mile begin? We asked Michael Gathage, a grower at Oserian Development Company? Are you asking about the harvesting procedures? We don’t know, was our prompt response, which Gathage, a seasoned grower laughed out loud about. Yes, he said, harvesting with laid down procedures. Tell us about the procedures. Gathage took a pair of scissors and with a surgeon’s precision demonstrated how to cut a flower stem when it is ready for harvesting. But before the cutting, a few other things are considered.

 Harvesting flowers is a science, he told us. It begins at the cut stage. “Different flower varieties have different cut stages, and determined by client requirements. The right cut stage is determined by harvesting flowers in advance and placing them in a vase room to monitor behaviour and vase life. If the flower droops it is not the right cut stage. The flower should open anytime from seven to fourteen days. Once the cut stage is determined, the grower can then grow the flower commercially on a large scale.” Says Gathage.

Harvesting of flowers is done twice daily at Oserian, in the morning and in the evening for uniformity. This may as well be thrice a day according to the number of flowers that are ready and available to be harvested.   A forecast done on the previous day helps determine what flowers to harvest, climatic conditions of the previous day are also checked.

The supervisor does a briefing during harvest on what is required.

“White varieties are more sensitive to damages, and are harvested using a sledge.” He furthers adds. Harvesters are required to use a special set of secateurs which must be clean and sharp to swiftly cut, hold the flower and put them in their arms in one movement keeping the stem intact. The tool is disinfected by constantly dipping it into a sanitizer to prevent the spread of bacteria to the stems  which pose a risk of blocking the uptake of water causing premature wilting.  

There are three key factors considered when harvesting flowers – shape, colour and the ring. Shape is different in each variety. The colour of the petals shows the flower is ready. The ring of the flower refers to the size of the flower. The petals must be slightly open and not too tight. The cut point is determined by market demand with high demand the cut point is upwards when branching while when the demand is low the cut point is downwards.

Harvesting follows the cultural activities which are done by skilled personnel at the right stage. During this point, all the cut flowers are collected in clean buckets filled with a post-harvest solution that contains food for the flowers. The harvest is transported to the pack house receiving bay, off loaded from the mode of transportation and placed in a shaded environment.

At Oserian, geothermal electric tugs have replaced trucks and every other minute they are seen snaking in and out of the pack house reception after discharging flowers. The tugs are part of the farm’s green energy initiatives aimed at reducing carbon footprints for a safer environment.

As the flowers arrive at the pack house reception, they are dipped in a calcium hypochlorite solution which protects them against botrytis. All roses are dipped in the solution due to susceptibility to the disease. Once dipped, shaken to remove excess water and after 15-20 minutes.taken into the cold storage chain where temperatures of 4 degrees Celsius  slow down metabolism to prolong  vase life. After being in storage for four hours, they are then graded as per clients’ specifications.

The standard operations procedures (SoPs) at the pack house change after every hour. Flowers found to have defects do not make it to the grading stage. The quarantine area in the pack house checks for pests and diseases above 10 %.  The most commonly checked diseases are botrytis, powdery and downy mildew, mites and damages. They also check on the mixed cut stage and wrong profile where reception records must mach with harvesting state details. Every bunch received is traceable to the greenhouse of origin and the staff who handled it and the time.  

Post-harvest activities, include cooling, defoliation, cleaning, sizing, sorting, bunching, packing, storing and shipping. The main objectives of post-harvesting activities is to keep the flower stems cool, avoid loss of moisture, avoiding physical damages to the buds and slow the metabolic activities.The quality of the stem flower is largely determined by the post-harvest activities.

Pests and Diseases

Due to the challenges of pests and diseases in flowers, breeders are increasingly developing varieties that are resistant.

“The most common pests and diseases in the flower farms at harvest are botrytis which mostly hits  when its rainy, or in high humidity.  To manage botrytis, we ensure there is minimal humidity among plants by providing good air circulation, we practice modified irrigation in cases where we have infected flower heads we remove them to prevent  spread of diseases.” Says Gathage.

 Thrips also pose a big threat to the flowers, traps are set to attract the pests that are known to like the colour blue. The traps are also laced with glue which traps the pests preventing them from reaching the flowers. Besides this, Integrated Pest Management (IPM) is used to fight pests whereby a predatory mite known as Phytoseiulus is released into the plantation to eat destructive pests such as the red spider mites. These phytoseiulus get rid of the pests and leave the flowers intact thus no chemical sprays are used in pest control.

story page 16-18 on the Aug- Sep Issue

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