Cut flowers and florist plants/greens

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Cut flowers and florist plants/greens

Description / shipment and storage / Risk factors

1.1 Introduction

International trade in flowers and plants is far more extensive than most people imagine. Most people know that The Netherlands play a large role in this trade. In fact, most people think of flowers – especially tulips – when they think of Holland. But tulips are not the only crop grown in Holland. Dutch growers produce an extremely varied selection of floral produce. And variety is to a high degree the foundation of the competitive nature of this sector of the Dutch economy.

Holland has become the world’s largest cut flower and pot plant exporter. But this small country is also the world’s largest consumer of domestic flowers and plants.

How did Holland achieve this prominent position as an exporter? First of all, Dutch agriculturists believe in cooperation. Researchers, training information services, producers and distributors all work together. Agriculture often is held up as an example to other sectors of the nation’s industry.

The degree of cooperation may be stronger in floral trade and production. Especially the cooperative auctions play an important part in floricultural sales. Holland is located near the most important markets, and, via auctions, offers a wide variety of high quality floral products, included imported varieties, all year. The liberal approach of the Dutch toward competition has heightened its impact on the international floral scene. Researchers, producers and exporters do not set out to compete with developments elsewhere in the world but try to use them to their own advantage. Many sectors of Dutch industrial life have been chosen to beat their competitors, rather than join them. This strategy of confrontation is not the style of the floral sector, which has always been characterised by a more liberal attitude. Cooperation is tailored for the advancement of those involved. This cooperation is evident not only in production and research but also in trading. The untrammelled growth of international trade, boosted by the creation of the European Community, has contributed to the rapid development of production and export of flowers and pot plants. The cooperative auctions have seized opportunities presented by these circumstances and a unique situation has come into being. Not only produce of member-producers is auctioned but, in addition, a wide assortment of flowers and pot plants from all parts of the world is siphoned through the system. Especially during the period that unfavourable climate prohibits growing some varieties in Holland. In this way a complete range of floral products is always available from the auctions. This is unique and set floriculture apart from other sectors of the agricultural industry. Export wholesalers are able to supply almost a complete range of products throughout the year, even during the winter. And this is very attractive to customers.

The traditional export market for Holland is neighbouring Germany, as well as other European countries. In recent years there has been healthy growth in trade with distant markets such as the USA, the Middle Eats, and even Japan, Australia and Hong Kong.

The close cooperation that characterises the Dutch floral industry, combined with continual improvement of the sector, justifies the hope that the industry will take an active role in current international developments. The Aalsmeer flower auction occupies a prominent place in the international flower and plant trading.

2.2 Botany

Plant materials from a wide range of taxa are grown and harvested as cut flowers or florist greens; these include ferns and lycopods, gymnosperms and angiosperms. Because of this diversity, these guidelines include a general review of post harvest requirements for cut ornamentals, followed by brief summaries of the requirements of a range of the most common materials used in commercial floriculture. The references cited are usually the most recent report on a particular crop, and therefore provide an entrée to the literature that is the basis for the recommendations.

2.3 Quality characteristics and criteria

Cut ornamentals are complex plant organs, in which loss of quality of stems, leaves, or flower parts may result in rejection in the marketplace. In some ornamentals, loss of quality may result from one of several causes, including wilting or abscission of leaves and/or petals, yellowing of leaves, and geotropic or phototropic bending of scapes and stems. In evaluating factors that affect the life of ornamentals and how to maximize their market life, it is important first to understand the diverse causes of quality loss.

Growth, development and aging. The whole plant and its individual organs are an integral part of the plant’s life cycle. Even when there is no senescence of floral organs or leaves, continued growth can result in quality loss: e.g., in spike-type flowers that bend in response to gravity. Flower senescence. The early death of flowers and greens is a common cause of quality loss and reduced vase-life for many ornamentals. Flowers can be divided into several categories on the basis of their senescence. Some flowers are extremely long-lived, especially in the Asteraceae and Orchidaceae families, while others are short-lived, including many of the bulb crops, like Tulip, Iris, and Narcissus. Wilting. Extended life for cut ornamentals depends absolutely on a continuing and adequate supply of water. Rapid wilting of shoot tips, leaves, and petals results from an obstruction of the water supply through the cut stems. Leaf yellowing and senescence. Yellowing of leaves and other organs (buds, stems) is commonly associated with the end of display life in some flowers; alstroemeria being an important example. Leaf yellowing is a complex process that may be caused by a range of different environmental factors. Shattering. Abscission and loss of leaves, buds, petals, flowers, or even branchlets is a process called ‘shattering’, and it is a common problem in cut flowers and potted plants. Very often, this problem is associated with the presence of ethylene in the air, but other environmental factors may also be involved.

2.4 Factors affecting postharvest quality

Maintaining the freshness of cut flowers and other ornamentals requires an understanding of the factors that lead to their deterioration. Variety. Many commercial cut flowers and cut greens are patented cultivars, characterized by specific attributes such as colour, form, disease resistance, and size. Sometimes, breeders fail to consider other commercially important attributes. For example, some of the modern alstroemeria cultivars have wonderful flowers, but their display life is short because of rapid leaf yellowing under commercial conditions. There is relatively little published information comparing the postharvest life of different ornamental cultivars.

Postharvest factors. What goes on in the greenhouse or field is an important determinant of the quality and life of cut flowers and foliage. Disease free plants that were properly irrigated and fertilized will produce flowers that look better and perform better in the vase. However, the large leaves on roses grown under supplementary light with CO2 fertilization make them more susceptible to postharvest wilting. Food supply. Starch and sugars stored in the stem, leaves and petals provide much of the food needed for cut-flower opening and maintenance. The levels of these carbohydrates are highest when plants are grown in high light with proper cultural management. Carbohydrate levels are, in fact, generally highest in the late afternoon: after a full day of sunlight. However, flowers are preferably harvested in the early morning, because temperatures are lower, plant water content is higher, and a whole day is available for processing the cut flowers. The quality and vase-life of many cut flowers can be improved by pulsing them immediately after harvest with a sugar solution. Pulsing is done by standing the cut flowers in the solution for a short period, usually less than 24 hrs., and often at low temperature. Typical examples include tuberose, where storage-life and opening are dramatically improved; gladiolus, where flowers open further up the spike, are bigger, and have a longer vase-life; and sweet peas, where vase-life was improved. Sugar is also an important part of the bud-opening solution used to open bud-cut flowers before distribution, and as part of the vase solution used at the retail and domestic level. Potted plants are able to provide their own food supply through photosynthesis if they are held in adequate light conditions.
Light. The presence or absence of light during storage is generally not a concern, except in cases where yellowing of foliage is a problem. The leaves of certain cultivars or chrysanthemum, alstroemeria, marguerite daisy and other crops can yellow if stored in darkness at warm temperatures. The blackening of leaves of cut Protea nerifolia flowers can be prevented by maintaining them in high light or by giving them a sugar pulse. This suggests that the problem is induced by low carbohydrate status in the harvested inflorescence. Water supply. Cut flowers, especially those with large leaf areas, lose water and wilt very rapidly. They should be stored above 95% RH to minimize water loss, particularly during long-term storage. Water loss is dramatically reduced at low temperatures, another reason for prompt and efficient cooling of cut flowers and potted plants. Even after flowers have lost considerable water (for example during transportation or storage) they can be fully rehydrated using proper techniques. Cut flowers will absorb solutions without difficulty providing there is no obstruction to water flow in the stems. Air embolism, plugging with bacteria, plant debris or dirt, and poor water quality reduce solution uptake.

1. Air embolism. Air embolisms occur when small bubbles of air (emboli) are drawn into the stem at the time of cutting. These bubbles cannot move far up the stem, so the upward movement of solution to the flower may be restricted. Emboli may be removed in many ways; e.g., recutting the stems under water (removing about 2 cm), ensuring that the solution is acid (PH 3 or 4), placing the stems in a vase solution heated to 40°C (warm, but not hot) or in an ice-cold solution (0°C), placing the stems in deep (>20 cm) water, or treating the flowers with a detergent ‘pulse’.

2. Bacterial plugging. The cut surface of a flower stem releases the contents of the cut cells (i.e. proteins, amino acids, sugars and minerals) into the vase water. These are ideal food for bacteria, yeasts and fungi, which grow rapidly in the anaerobic environment of the vase. Slime produced by the bacteria, and the bacteria themselves, can obstruct the water-conducting system. This problem must be addressed at every step of the postharvest chain by:

  • Using clean water for making postharvest solutions.
  • Cleaning and disinfecting buckets.
  • Using white buckets – dirt is easier to see in a white bucket.
  • Including a biocide in all buckets and vase solutions. Ca(OCl)2, NaOCl (‘Clorox’), A12(SO4)3, and salts of 8-hydroxyquinoline are commonly used bactericides. An acidic solution also inhibits bacterial growth.

3.Hard water. Hard water frequently contains minerals that make the water alkaline (high PH). Water movement in flower stems is drastically reduced when the water is of high PH. This problem can be overcome either by removing minerals from the water (by using a deionizer, still, or reverse osmosis system) or by making the water acid (ca. PH 3,5). Citric acid is commonly used as a safe acidulant.

Water quality. Chemicals commonly found in tap water are toxic to some ornamentals. Sodium (Na), present in high concentrations in soft water, is toxic to carnations and roses and will cause salt burn (burning of the leaf tips and margins) in potted plants. Fluoride (F) is very toxic to gaillardia, gerbera, gladiolus, roses and freesia. Fluoridated drinking water contains enough F (about 1 ppm) to damage these flowers. Growth Tropisms. Certain responses of cut flowers to environmental stimuli (tropisms) can result in quality loss. Most important is geotropism (bending away from gravity) and phototropism (bending towards light). Geotropism often reduces quality in spike-flower crops like gladiolus, snapdragon, lisianthus, and gerbera, ecause the flowers and spike bend upward when stored horizontally. These flowers should be handled upright whenever possible. Mechanical damage. Physical abuse of cut flowers and foliage results in torn petals, damaged leaves, broken stems. Obvious injuries are undesirable for aesthetic reasons, and disease organisms can more easily infect plants through injured areas. Additionally, respiration and ethylene evolution are generally higher in injured tissues, further reducing storage and vase-life.

2.5 Horticultural maturity indices

Minimum harvest maturity for most cut flowers is the stage at which harvested buds can be opened fully and have satisfactory display life after distribution. Many flowers are best cut in the bud stage and opened after storage, transport or distribution. This technique has many advantages, including reduced growing time for single-harvest crops, increased product packing density, simplified temperature management, reduced susceptibility to mechanical damage and reduced desiccation. Many flowers are presently harvested when the buds are starting to open (rose, gladiolus), although others are normally fully open or nearly so (chrysanthemum, carnation). Flowers for local markets are generally harvested much more open than those intended for storage and/or long-distance transport. Cut foliage is harvested when the uppermost leaves are fully expanded to avoid postharvest wilting of the shoot tips.

2.6 Food supply

The high respiration rate and rapid development of lower buds and flowers indicate the need for a substantial carbohydrate supply to the flowers after harvest. Starch and sugar stored in the stems, leaves, and petals provide much of the food needed for cut-flower opening and maintenance. These carbohydrate levels are highest when plants are grown in high light conditions and with proper cultural management. Carbohydrate levels are generally highest in the late afternoon, after a full day of sunlight. However, flowers are preferably harvested in the early morning, because temperatures are low, plant water content is high, and a whole day is available for processing the cut flowers. The quality and vase life of many cut flowers can be improved by pulsing them after harvest with a solution containing sugar. The cut flowers are allowed to stand in solution for a short period, usually less than 24 hours, and often at low temperature.