Articles

Post Harvest Management of Carnation

Dr. R. Chandra

In many countries, carnation is one of the most popular cut flowers and of highest economic importance in the floriculture industry. Cut flowers of carnation are used in two forms i.e., the standard type in which carnations have one flower on a stem and the spray type in which carnations have multiple flowers on a stem. In recent years, spray type carnation flowers have become popular because they can be grown with less labour and meet modern consumer’s demand. Indian places having cool climate like Kashmir, Kullu Valley, Kalimpong, Bangalore etc. are most suitable areas for the production of cut flowers which may be exported to Europe and U.S.A. Postharvest management chain needs to be strengthened and standardized for minimizing losses and maintaining quality blooms the following heads have to be considered.

• Harvesting stage
• Pre cooling
• Grading
• Storage
• Pulsing
• Packaging
• Transport
• Retail florist care & handling
• Sleepiness

HARVESTING STAGE:

Postharvest stage is the most important stage which decides the market. As convention paintbrush stage is the desirable stage for harvesting. But now-a-days tight buds are also preferable for distant market.

BUD OPNEING: Beyond ‘paint brush’ stage.

1. A.   Standard Carnation:  

To increase number to flowers of commercial quality, we may harvest carnation at different bud stages. For standard carnations, bud opening through chemical treatment makes it possible to obtain an additional crop from nursery even though cultivation period has ended. In such a situation, a number of small buds which are unable to open in water remain on the plants. Also, harvesting flowers at the buds stage correlates the development of new buds on plant and thus produces the additional crop.

Flowers of commercial quality may be obtained from even “green pea” size buds, although these flowers have smaller diameter and shorter vase life than those from buds harvested as more advanced stages of development. Flowers of excellent quality may be obtained from mature tight buds and from buds at the stage, the two stages most suitable for long term storage. Immediately after harvest, buds should be placed in an opening solution. They should not be placed in water or left dry.

Standard carnation flowers should be carefully graded according to length and bud size and tied bunches of 20-25 flowers. Stem ends should be re cut just before they are placed in the opening solution. Shallow container should be use to hold bunches of buds vertically without crowding and to facilitate access of light to the leaves.

If large numbers of buds are to be open simultaneously, sets of containers connected by tubes and equipped with a device for controlling the level of the opening solution may be used. The level of the solution in the container should not exceed 5cm. Solution containing Ag NO₃ (50ppm) + 8-Hydroxy quinoline citrate (200ppm) + sucrose (70ppm) may be used.

Carnations cut at the ‘tight buds’, ‘cross’ and star stage develop to the commercially desirable point after 9-10, 6-7 and 2-5 days respectively depending upon the temperature and the quality of the plant material. Smaller buds require a longer period for opening. Specifically buds cut at the “green pea” stage require 18 – 21 days and at the bud cut at ‘hazelnut’ stage require 15-18 days. The chemical solution used for bud opening remains active for 7 days. Thus at needs to be replaced each change of solution, stem ends should be re cut.

1. B.    Spray Carnation:

Spray carnations harvested when one flower on a stem shows colour may be opened under the same conditions as standard carnations by using the some chemical solutions.

PRECOOLING:

It is the low temperature treatment to cut flowers after harvest to remove field heat, thus lowering the respiration rate and increase in vase life. For carnation, the pre cooling temperature is 1⁰C  Bhattacharjee (1995).

GRADING:

Society of American florists set following inspection criteria for carnation cut flowers.

• Bright, clean, firm flowers and leaves
• Fairly tight petals near the centre of the unopened flowers
• Symmetrical of flower shape and size
• No split or mended calyx
• No lateral buds or suckers
• No decay or damage
• Straight stem and normal growth
• No sleepy appearance

Grades:

Four important factors decide the grade of flowers (i.e. Blue, Red. Green – Fancy, standard & short respectively) viz:

i)                    Minimum flower diameter

ii)                  Minimum length

iii)                Stem strength

iv)                Defects

Grade	Minimum flowers diameter (mm)	Minimum length (cm)
Blue (Fancy)	Tight  –  50 Fairly tight  –  62 open  –  75	55
Red (Standard)	Tight  –  44 Fairly tight – 56 open – 69	43
Green (short)	Tight  –  none Fairly tight  –  none	30

(iii) Stem strength:  Shall be determined by holding the stem horizontally at a point 25 mm above the minimum length for the grade, and the deviation of the flower head shall not be more than 30⁰C below the horizontal place with the natural curvature of the stem down.

(iv) Defect: Blue grade shall consist of fully symmetrical brown heads, singles, and sleepy appearance, splits, discoloration, insects, diseases and other damages. It shall have straight stem.

Red grade, other than diameter of flower and length of stem, it shall have the some requirement.

STORAGE:

Open flowers standard carnations:

Flowers harvested at ‘paint brush’ stage can be stored dry in moisture retentive boxes at – 0.5 to 0 ⁰C for 3 – 4 weeks. Fully open flowers are better stored in a floral preservative solution at 3-4 ⁰C because lower temperatures may cause injuries and discoloration of the petals in some cultivars, especially when the storage period is longer than 2 weeks. Prior to prolonged storage, either dry or wet, flowers should be treated with Silver thiosulphate (STS). During wet storage, high R H of 90-95% should be maintained, and flowers must be shielded against direct streams of cold air from the cooler.

Bud cut standard carnations:

          Carnation to be subjected to prolonged dry storage should be harvested at the stage of matured, large but tight buds with calyxes filled with petals just beginning to appear on the upper portion (i.e. at cross stage). Such buds may be stored as long as 5 – 6 months (except for cultivars of yellow colour) it the quality of harvested stem is very good. Flowers harvested when partly open, at the ‘star’ stage when petals emerge about 0.5 cm above the calyx, may be storage up to 8 weeks. Flowers desired for storage should be free of diseases and pests.

All the heads should be kept on the same level to allow equal access of tight to the buds during their opening after storage. Stem ends should be re cut at he same point near the base to ensure their submergence to equal depth is a floral preservative solution.

Flowers desired for prolonged storage should be protected against gray mould by spraying just before harvest or by dipping whole flowers in a fungicide solution for a few second just after harvest. Buds then should be conditioned in a solution containing STS and 70-100 g/L (7-10%) of sucrose. Conditioning may be carried out in cold storage at 0-1 ⁰C using a solution warmed to 40 ⁰C in which flower stem are submerged 3-5 cm. Buds should remain in the conditioning solution 20-24 hours.

If conditioning is conducted at a higher temperature (i.e. 10-20 ⁰C), the solution does not need to be warmed, but after conditioning, the flowers should be transferred to cold storage and cooled to 0-1⁰C. In order to prevent the development of gray mould and other diseases, flowers which have not been preceded and flowers which are still wet must not be packed.

The buds should be packed at a low temperature, close to 0 ⁰C, wrapped in paper and then placed in foil bags and tightly sealed inside. The optional temperature for storing carnation is 0-0.5⁰C. After storage, packages containing flowers should be kept in a room at 8-10 ⁰C for 2-3 hours to avoid temperature stress. Flowers should then be unpacked and transferred to a warmer room. Stems should be re cut 3-5 cm from the base and buds placed under proper conditions for opening to the commercially accepted stage.

Spray Carnation:

They are stored similar to standard carnations. However, the storage period is shorter for spray carnations. Without chemical treatment, spray carnations may be stored in water or in moisture retentive boxes up to 2 weeks as – 0.5 ⁰C to 0 ⁰C. Spray carnations harvested in the bud stage, when one floral on the stem shows colour, may be stored dry for 2 months in a cold room if handled in the some manner as standard carnations.

Storage method sand conditions

          Maximum storage period of carnation cut flowers in different methods are as follows:

• Dry storage period:- storage temperature 0-1⁰C, Maximum storage period  16-24 weeks.
• Wet storage period:- Storage temperature 4 ⁰C, Maximum storage period  4 weeks.
• Controlled Atmospheric storage/Modified Atmospheric storage:- CO₂ (5%), O₂ (1-3%), storage temperature 0-1⁰C storage period 30 days.
• Low pressure storage:- Hg (40 – 60 mm), low temperature 91 days.
• Cold storage (4⁰C) 10 days.

PULSING/LOADING:

Pulsing is the Postharvest treatment of cut flowers (before packaging and transport) with sucrose, anti ethylene and anti microbial compounds, which causes the flower fresh till it reaches to consumer. Here concentration of sucrose is important. For carnation sucrose (20%) concentration for 12 – 16 hour at 20 ⁰C, 2000 lux light intensity is the optimum for pulsing or loading (Singh and Hussain, 2001).

PACKING:

• Carnations are packed in corrugated cardboard container (CCC).
• The CCC size is 122 cm x 50 cm x 30cm, which contains 800 carnation cut flowers.
• The boxes or container should be well insulated and should have a lining of vapour barrier like polythene lining to help in maintaining high relative humidity inside the package.
• Bunches of 25 flowers are then placed in these boxes with one half of the total number of bunches oriented on each end of the container.
• Close packing of flowers helps to minimize the distance for heat exchange between flowers and container.
• Newspaper layers are placed between the flower layer to maintain high humidity and then, when the container across the box to cover the flowers completely.
• A strip of wood is inserted laterally in the middle of the box, forced downwards and stapled in to place to stems during shipping.
• The lids are fixed to the box by taping or twining it. Sometimes the top lid is made partially or completely transparent for viewing the flowers without disturbing them.
• Ethylene scrubbers containing KMnO₄ may be kept, inside.

TRANSPORT:

• Both standard and spray carnation cut flowers are suitable for dry transportation over a period of several days.
• Cool chain system (low temperature) is important during transportation to slow down respiration, transpiration, slating of bud opening etc.
• For rapid cooling of cut flowers various systems like blowing fan forced cold air over open boxes, pushing cold air through vented boxes, vacuum cooling etc. can be adopted.
• Humidity during transportation should be maintained at the level of 95-98%/
• Merely two pollinated carnations in a box can considerably decrease the longevity of other so KMnO₄ may be used in ethylene scribblers during packaging.
• Trunk shipment: – for shorter than 20 hours.
• Air shipment:– Quickest, flowers should be treated with STS (ethylene decreasing) Costly.
• Sea Shipment – Take more time, preferably, cheap.

RETAIL FLORIST CARE AND HANDLING:

Unpacking and Reconditioning:

Unpacking should be carried out with due care and attention. If the flowers ever transported at an optimal temperature, they should simple be unpacked and placed in water or floral preservative solution. If the flowers were transported at too low temperature, they should first be checked for chilling injuries. Uninjured flowers should be placed in a cold room at 5-10 ⁰C for 12-24 hours. Afterwards, they should be transferred to higher temperature and repacked. Such treatment prevent temperature stress and helps flowers to recover minor injuries.

After unpacking the flowers should be placed in racks appropriately designed to protect them against crowding. Lowermost leaves should be removed so they will not decay in the vase water. Outermost petals if injured may be carefully removed. Stem-ends should be cut at a slant in order to increase the area so contact between the surface of the stem and water and thus to improve water uptake. Cut flowers (wilted) thus may be conditioned to maintain turgidity.

Floral Preservatives:

Sucrose may be given according to the need. But treatment with STS is important. Preservative solution (AgNO₃) [broken down by light] causing brown stem end should be avoided.

1. Temperature: Cut flowers stored in the florist shop at 4-5 ⁰C.
2. Humidity: About 90% humidity should be maintained to prevent wilting of petals.
3. Light:  Light intensity of 100 lux is maintained to prevent of leaves but not important here.
4. Ethylene: In florist shops, ethylene polluted air combustion gases, plastic flower, polythene foils which may give off ethylene should be avoid. There should be proper ventilation. If required flowers should be treated with STS.

SLEEPINESS:

In every step sleepiness of carnation should be avoided.

Causes:

• Exposure to ethylene gas
• Water stress
• When flowers stored for a longer period
• When exposed to high temperature
• When flowers were kept in cold storage for some time and then brought out for grading and packing during which flowers got warmed.

Control:

• Cooling of flowers at – 0.6 to 0.0⁰C before shipping.
• Rapid cooling of flowers in packing helps to reduce the water loss and prevent sleepiness.

SUMMERY:  For sending quality carnation cut flower to consumer level we should have strategies viz; harvesting at paintbrush stage or tight (distant market), Pre cooling at 1⁰C, growth of flowers (55 cm minimum stem length, flower dia, 7.0 cm & straight stem), dry stored at 0-1⁰C or wet storing at 4⁰C or CA storage, at 5% CO₂, 1-3%, O₂, temperature at 0-1⁰C, or  low pressure storage, at 40-60 mm Hg; pulsing with 10% sucrose and ant ethylene solution, packaging 35 flowers in each bundle in 122 cm x 50cm box size and their proper reconditioning & care at florist shop. By these post harvest management or cut flowers no dust, we will catch the consumer’s eye for carnation.