To study the harvesting and post-harvest handling of cut flowers

Horticulture Guruji

Exercise 10

To study the harvesting and post-harvest handling of cut flowers

HORT 222

A cut flower may be defined as a flower or an inflorescence containing more than one floral unit in the opened or unopened state which is harvested and marketed for ornamental purposes. Cut flowers in general are highly perishable commodities and highly vulnerable to huge post-harvest losses.

Most of the cut flowers complete their life cycle in two distinct phases. The first stage is flower bud growth and development of the flower to full opening. The second stage is maturation, senescence, and wilting. Handling techniques to enhance cut flower longevity must achieve two seemingly conflicting purposes, promotion of growth process in the first stage and retardation of metabolic processes leading to senescence in the second stage.

 

Harvesting:- Harvesting is the process of detaching flowers from the plant in a scientific way using sterilized equipment. For this, the maturity indices of the various cut flowers are to be known. Flowers cut prior to their maturity indices may wilt before reaching wholesalers. Harvesting should be preferably done in the evening.

 

Maturity indices of various cut flowers

Sr. No.

Cut Flower

Harvesting index

1

Rose

One petal unfolds

2.

Carnation

Petals just unfold

3

Gerbera

When the outer 2 rows of disc florets open perpendicular to the stalk.

4.

Chrysanthemum

When ray florets are fully opened and disc florets are visible in the centre of the flower head.

5.

Marigold

Fully opened flowers

6.

Tuberose

Basal pair of florets open

7.

Gladiolus

When the basal floret shows its petal colour.

 

Post harvesting chain of cut flowers

Conditioning

Conditioning or hardening is a simple process where the flowers are kept or made to stand loosely in a big container of water so the air circulates around the stems. The main purpose of this treatment is to restore the turgidity of cut flowers after they have suffered from water stress during handling in the field, greenhouse, or during storage and transport. Flowers can be conditioned in the dark so that their stomata will close, reducing the amount of water loss by transpiration. Conditioning is achieved by de-mineralized water supplemented with germicides and acidified with citric acid to pH 4.5-5.0 but with or without sugar. Hydration is improved when water is de-aerated or acidified or when welting agent like Twin 20 at the rate of 0.01-0.1% is added. Flower stems should be placed in warm water or in a preservative solution in plastic jars at a depth of 2-4cm and held at room temperature or in cold storage for several hours.

Chemicals for conditioning flowers:-

No.

Cut Flower

Floral Preservative

1

Chrysanthemum

AgNo3 (25ppm) + sucrose (50g/l) for 16 hours at 21o C

2

Carnation

STA 0.5 millimolar +Sucrose (70-100g/l) for 20-24 hours

3

Rose

Citric Acid (500ppm) in cold storage at 0-1oC

 

Pre-cooling:- Packed or unpacked flowers have to be pre-cooled before storage or shipment. The time between harvest and pre-cooling should be as short as possible. Forced air cooling is most effective in removing the field heat from flowers. Pre-cooling is done by forced air cooling or cooling to bring down the temperature to 1oC in a short period.

 

Pre-cooling temperature is suitable for flower crops:-

Flowers

Pre-cooling Temperature (oC)

Chrysanthemum

0.5-4.0

Carnation

1

Gerbera

2

Gladiolus

4-5

Rose

1-2

 

Pulsing:- The absorption of a chemical solution containing sugar and germicides through the lower cut portion of flower stems is known as pulsing. This treatment should be performed under the temperature of 20 – 25oC at a light intensity of 2000 lux. Pulsing may be used by growers, wholesalers, or retail florists to extend the subsequent vase life in water. Pulsing is of great value in prolonged life, promoting opening and improving colour and size of petals of cut flowers.

 

Chemical for pulsing of different cut flowers:-

No

Flowers

Chemical solution

1

Rose

Sucrose (4-6%) for 12 hours or sucrose (3%) for 18-24% hours, Silver thiosulphate (0.5mM) for 45 minutes;

2

Gladiolus

Sucrose (20%) for 16 hours

3

Carnation

Sucrose (10-15%) or Physan (200ppm) for 16 hours

4

Chrysanthemum

Sucrose (5%) for 16-20 hours.

 

 Impregnation:- Impregnation of cut bases of flowers with a high concentration of Silver nitrate (AgNo3) or Nickel chloride (NiCl2) or Cobalt chloride (CoCl2) for 10-15 minutes greatly improves the longevity of several flowers. Here, the Ag++, or Ni++ or Co++ ions stay at the base and protect from microbial blockages.

Grading:- Damaged or diseased blooms have to be discarded. Diseased flowers will contaminate others. Hence only good quality flowers should be stored.

Grading is also done based on size, flower quality and also based on the standards recommended for various cut flowers.

Bunching:- Flowers should be bunched before storage and tying should be firm but not too tight. If flowers are too tightly crowded in storage, mould growth is favoured and rapid cooling is retarded.

Wrapping:- Just before packing the flowers in cartons, flowers are wrapped individually in thin polythene sleeves. Roses are wrapped in butter paper sheets or waxy sheets.

Packing:- Packing is done to protect flowers from physical damage, water loss, and external conditions during transport. Packing can take many forms from flower cups up to sleeves, boxes, bulk bins, sea, and air containers. An ideal packing should promote low respiration and low transpiration. Two types of packing can be done;

Wet packing:- In wet packing, stalks have a piece of moist cotton at the cut end of the flower, or the spike is kept immersed in a test tube containing vase solution.

Dry packing:- In dry packing, flowers are as such stored in polythene covers. Dry-packed flowers require quick pulsing treatment.

Cold Storage:- The cold storage of cut flowers facilitates adjustment of flower supply to market demands, enables accumulation of large quantities of flowers for distant shipments, and makes it possible to prolong the period of flower sale. Low-temperature treatment during storage of cut flowers reduces the entire metabolism in tissue, slows down the respiration, transpiration, ethylene production, and activities of fungi and bacteria.

  1. Wet storage, where flowers are kept during storage with their bases in water for short period, and
  2. Dry storage, fresh flowers are harvested in the morning, graded and sealed in plastic bags or boxes for longer periods.

Ideal storage temperature for cut flowers

Crop

Dry storage temp OC

Wet storage temp OC

Rose

0-1

4

Chrysanthemum

0.5-0

Gerbera

2

4

Carnation

0.5-0

4

 

All Types of Horticultural Crops