1. Conditions During Production
2. Stage of Development During Production
3. Availability of Food for Respiration
4. Light
5. Temperature
6. Water and Cut Flowers
7. Floral Preservatives
8. Plant Growth Regulators
9. Insects and Disease
10. Handling Damage
11. Storage
12. Miscellaneous Chemical Effects
13. Floral Foams
14. Toxicity of Flowers to Humans
15. More Information
1. Conditions During Production
Although it appears obvious that the circumstances under which plants are grown can influence the life of flowers cut from them, very little data are available to substantiate this presumption. In general, any condition, be it nutritional, moisture, or light intensity, which induces the growth of lush, soft tissues, may predispose harvested- flowers to infection by disease organisms and invasion of insects. This has been documented in Chrysanthemum and Carnation. Temperature is also a factor. Lowering the night temperature during the last few weeks of production has, in the case of Poinsettia, been shown to improve the lasting quality of cut Poinsettias.
2. Stage of Development at Harvest
The longevity of many cut flower species is related to the stage of their development at the time of harvest. Vase life is usually shortened when flowers are harvested at relatively advanced stages of development, but there are exeptions to this, such as for instance, Narcissus, which appears to do best when harvested open, and Anthurium, which must be beyond a certain stage of development for best keeping quality.
Many flowers will last longer when cut at very early developmental stages, and a large number of species do exceedingly well if harvested in the bud stage, and opened in special opening solutions (ie. standard chrysanthemums, carnations, lilies, etc.) .
Bud cutting has a number of benefits aside from allowing a longer period before the onset of senescence. Flower buds are less damaged by gases such as ethylene than are open, mature flowers. In addition, open blooms are more easily mechanically damaged in transit and require more care in handling than buds. There are also varietal differences, in ability for cut buds to open properly. Most iris varieties, for instance, will develop if cut when a small amount of color extends above the sheath, but one variety (Professor Blaau) must be harvested at a more advanced stage, when the edge of one of the petals has opened, in order for the flower to properly develop in an opening solution.
3. Availability of Food for Respiration
All living things require a source of food, which, when consumed in the process of respiration, will provide a source of energy for maintenance and development. Cut flowers are no different. When attached to the plant, the flowers are supplied with a constant source of food in the form of carbohydrates produced by photosynthesis. After cutting, however, this food source is no longer available if flowers are kept in low levels of light. If no external food is supplied to cut flowers, they will usually last longer if they are harvested after a period of photosynthesis, such as would occur in the afternoon, after exposure to light, rather than in the morning, when a large amount of food is exhausted after an evening of darkness. Cut flowers use sugar as a food source.
Practically speaking, the best way of insuring that a sufficient supply of sugar is available is to include some in the vase water. The sugar enables buds to develop properly and attain larger sizes, in addition to increasing cut flower longevity. Sugar may be dissolved in the water at concentrations of 4 to 7%, to be fed constantly, or else fed in a pulse of 5 to 12% overnight. Flowers pulsed in this manner are then usually transferred to plain water for the remainder of their life. The foliage of some flowers, such as alstroemeria and roses, may become yellowed or burned by excessive sugar uptake. This may be remedied by first hydrating the flowers in a solution without sugar, and then placing them in a floral preservative, or else by using a lower concentration of sugar in the floral preservative.
Very little research has been done to examine the effects of light on cut flowers, since it not known to drastically affect their longevity. It is known that exposure to light of bud-cut flowers promotes intensity of color when they are opened, and inhibits yellowing of foliage during storage of several species. However, there is almost no data on the effects of light on vase life.
The rate of senescence or aging in flowers which are held in water is directly proportional to the rate of respiration, which is dependent upon the temperature. High rates of respiration can lead to rapid depletion of carbohydrates. This means that holding at a higher temperature will result in a much shorter vase life for flowers in water. Refrigeration is used by florists so that utilization of carbohydrates in respiration is retarded, giving the consumer the greatest value possible. Unopened cartons of flowers generate quite a bit of heat, even in cool areas, since the heat generated by respiration has no chance to be dissipated. Therefore, flowers must be brought to storage or holding temperature as quickly as possible, and proper refrigerator temperatures maintained. Of course, addition of carbohydrates to the vase water minimizes the problem of carbohydrate depletion at elevated temperatures.
Some species, especially those from the tropics, can sustain chilling damage if refrigerated at 40-45F (4-7C). Where appropriate, proper holding temperatures for specific crops are noted as follows:
6. Water and the Hydration of Cut Flowers
Stem Blockage and its Causes:Blockage by Air in the Stem
When stems are normally cut, air is drawn into the stems for a short distance. These air plugs, or embolisms, can prevent the normal movement of water through the stem when the flowers are placed in water. This loss in ability to take up water can be minimized by placing stems in slightly acidified water (pH 3-4) or by recutting stems under water. Using warm water at about bath temperature, 100F (38C) also decreases the formation of embolisms.Physiological Blockage
With very few exceptions, the amount of water taken up by a flower declines with time. The cause for this decrease in ability to take up water is known as called 'Physiological Blockage'.Physical Blockage by Microorganisms
The effects of bacteria and fungi can often be seen when one allows foliage to remain in the vase water to rot, fouling and clouding the solution. Microorganisms like these thrive and multiply on plant tissue, and are taken up into the stem and form a physical barrier to water uptake, and consequently, the flower wilts and dies. These microbes can use sugar very efficiently for food, and since the addition of sugar to the vase water makes flowers last longer, it is obvious that the addition of sugar to the holding solution would result in rapid growth of microorganisms, which would be drawn up into the stem to cause an obstruction to water movement. The consequence is rapid wilting of flowers. In order to prevent blockage by microbes, a biocide is always included hen sugar is added to the water. The simplest floral preservative contains sugar and a biocide, and in addition to these, floral preservatives usually contain other compounds as well, in order to further enhance flower quality. The most common biocide is 8-hydroxyquinoline ci::rate (HQC), which retards the growth of microbes. and is fairly safe to use with most species of flowers, although it is toxic to some species. HQC is slightly acid, which enhances water uptake. The normal concentration for using HQC is 200 ppm. Household bleach (5.25% sodium hypochlorite) has also been used as a bio-cide, at 20-50 ppm. It is effective in reducing odors in solutions containing stock (Matthiola) , but the chlorine odor itself is also somewhat objectionable.To Top of Page Properties of Water
If at all possible, it is wise to use water from which salts have been removed by passing it through a column or with the use of reverse osmosis equipment; the resulting water is known as deionized water (DI).
Water which is somewhat on the acid side (about pH 2.5-3.5) is taken up by flower stems much more readily than alkaline ater. Since the water supply in many areas contains minerals which make the water -,er, 'hard' or alkaline, hydration of flowers in these areas often presents a problem.
Alkaline water is frequently acidified by addition of citric acid or aluminum sulfate. Citric acid is cheaper to use, and is most effective. A general rate of citric acid cannot be given because it varies, depending on the type and amount of mineral content of the water. The best way to determine the correct amount of citric acid required to bring the any tap water to a pH of 3.5 is to make a stock solution of citric acid and add small amounts to the water or preservative, checking the pH after each addition, until a pH of 3.5 is attained, and to make a note of the total amount of stock solution used. Hard water generally requires from 300 to 500 ppm of citric acid.
Aluminum sulfate is less desirable as an acidifier, and may even be phytotoxic at low pH. Hydroxyquinoline citrate (HQC) lowers the pH somewhat, and should be included in the water when determining the rate of citric acid, if HQC is also to be used in the holding solution.
In the event that these chemicals are not available, the juice of one lemon in one liter of water will usually lower the pH to about 3, if the mineral content of the water is low. High alkaline hard waters requires larger quantities of lemon juice. In a pinch, a small portion of lemon juice concentrate will do the job.
Water uptake is also governed by the temperature of the solution. At 100F (380C) water is less viscous, and is taken up by flowers much more readily than at a temperature of 36F (2C).
Aluminum sulfate is less desirable as an acidifier, and may
even be ph,,totoxic at low pH.
Hydroxyquinoline citrate (HQC) lowers the pH somewhat, and should
be included in the water when determining the rate of citric acid,
if HQC is also to be used in the holding solution.
In the event that these chemicals are not available, the juice of one lem-c>n in one liter of water will usually lower the pH to about 3, if the mineral content of the water is low. High alkaline hard waters requires larger quantities of lemon juice. In a pinch, a small portion of lemon juice concentrate will do the job.
Water uptake is also governed by the temperature of the solution. At IOOF (38C) water is less viscous, and is taken up by flowers much more readily than at a temperature of 36F (2C).
Numerous commercial preservatives are available for use in increasing the lon_zevity of most cut flowers. Most of these preservatives do an excellent job of improving vase life. It is important that directions for their use be closely followed in order for them to act effectively.
There is no single preservative which gives optimum results with all flowers. Like individuals, cut flowers vary in their requirements, and each should be treated differently.
Certain chemicals, called Plant Growth Regulators, have the property of being able to control plant growth and/or development:. Some of these chemicals are manufactured synthetically, whereas others (The Plant Hormones), are synthesized or produced by the plants. The following plant growth regulators have been reported to affect the aging and longevity of cut flowers:
(1). Ethylene
Ethylene is an odorless, colorless gas which decreases the longevity of cut flowers by hormonally causing them to wilt rapidly (ie. carnations), promoting the shedding or shattering of petals (ie, snapdragons) , or by otherwise damaging the petal tissue (ie. orchids). Not only is it found in the atmosphere as a product of incomplete combustion, but it is also produced by aging plant tissues such as ripening fruit, and by senescing flowers, themselves.
Flowers vary in their sensitivity to ethylene, but those that are sensitive may be killed by concentrations as little as less than 1 part per million in less than 12 hours exposure. To avoid the detrimental effects of ethylene, keep flowers away from gas leaks, smoke, ripening fruit, and other aging flowers. Holding and working areas should also be well ventilated.
Sensitivity to ethylene is also reduced at lower temperatures, so it is important to bring flowers to their holding or storage temperature as quickly as possible, and to prevent heat from building up in unopened shipping car-tons.
Treatment with silver thiosulfate has been found to eliminate or at least reduce the effects of ethylene on numerous sensitive species of cut flowers, even when they are exposed to the gas.
(2). Auxin
There is data which indicate that endogenous auxins exert control over cut flower aging processes, but almost nothing is known of commercial applications of this information. However, it is known that small concentrations of auxins such as 2,4-D, which is a synthetic herbicide, can rapidly kill cut flowers. Containers which have been used for holding any sort of weed killers should therefore never be used for cut flowers.
The curving upward of the tips of some of the spike types of cut flowers such as snapdragons, which are held in a horizontal position, is caused by gravity, and is an auxin-mediated effect. These flowers should always be stored in an upright position. Even short periods held horizontally will be e to cause stems to bend.
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Flowers are susceptible to injury from insects and disease organisms during production. Such injury reduces their quality and longevity. After harvest, cut flowers are predisposed to infection by Botrytis or 'Gray Mold', particularly if moisture drips or condenses on flower tissue surfaces. Unventilated stored flower cartons which are left in the heat and then chilled will contain large quantities of condensed moisture, which usually results in spoilage caused by 'Gray Mold'. Excessive storage at the proper temperature can also lead to the same disease.
Injury to cut flower tissue can decrease vase life by making tissues more susceptible to infection by bacteria and fungi. Affected flowers are caused to produce large quantities of ethylene, which in turn can promote rapid floral senescence.
In many instances, an increase in cut flower storage time results in a subsequent decrease in vase life. Flowers are at times pulsed with silver thiosulfate and/or preservative prior to storage to increase vase life. Conditions in storage depend upon the cultivar; some are stored dry, some in .ater or a preservative solution, and other culti,ars do equally well hether stored wet or dry. The proper temperature, relative hmidity, and moisture barriers used are important factors, and each should not be overlooked in order to achieve best results. Proper storage handling techniques will insure maximum life for most cut flowers, but it must be remembered that there is a limit of time for storage of each flower type with satisfactory vase life performance.
12. Miscellaneous Chemical Effects
Fluoride has a detrimental effect on plants in the lily family,
causing scorching of leaves. Cut flowers in this family are also
affected by fluorine, which is found as an additive to most drinking
waters. Floride is most damaging at low pH, which is best for
optimum water uptake. It is therefore best to avoid waters having
high fluoride contents.
The sap exudate from the bases of stems of some flowers also influences
the vase life of other species held in the same container when
drawn up into the vascular tissues. This has been observed to
be the case with Narcissus, which exudes a sap that shortens the
life of a number of other cut flowers.
Anchorage of stems has always presented a problem to floral designers, but the availability of open celled floral foams has done much to solve this problem by allowing positive placement of flowers in a material which is conducive to good water uptake and lasting qualities.
To insure proper performance, foams should be thoroughly soaked in solution without leaving air pockets, which develop when the foam is held under the surface of the water. Instead, allow the foam to float on the solution surface, gradually absorbing the solution. Don't try to accelerate absorption.
Make sure that stem bases are in contact with the foam. If a flower is inserted too deeply, it is always best to remove and reinsert the flower, and not merely partially withdraw it from the foam which would leave a gap between the foam and the base of the stem.
Most flowers benefit by uptake of a floral preservative. Floral foams should always be soaked in a preservative when used with such flowers which are normally treated with preservatives.
Recent tests have indicated the presence of substances in floral foams which cause a reduction in vase life. Some brands contain higher levels of these substances than other brands. The effects of these substances may be minimized by soaking the foam in floral preservative, rather than in plain water.
Many excellent brands of floral foams are now being marketed. It is a wise practice to compare the longevity of flowers in a preservative solution in a vase with similar flowers in a foam soaked in the same preservative to determine whether there is any decrease in longevity as a result of using the foam. If a large difference is observed, another brand should be tested, until one is found which gives a longevity reasonably similar to that found in fic-ers in a vase solution.
14. Toxicity of Flowers to Humans
Ailments sometimes occur as a result of handling flowers. A glycosidic substance found in Tulips and Alstroemeria has been identified as the cause of a type of dermatitis which can be quite incapacitating, giving rise to a classical syndrome known as 'tulip fingers'.
A skin rash called sporotrichosis can also contracted by contact with a fungus which thrives in wet floral storage areas. Simple skin afflictions may also occur from allergenic reaction to various substances derived from plant tissues, or from contact ith pesticide or herbicide residues.
Florists who develop skin rashes should take steps to set up a barrier by dusting hands with talc, and putting on surgeons' rubber gloves, or by coating the hands with a sealing coating material.
Several excellent sources are available for obtaining information on increasing longevity of Cut Flowers. These are:
Flower and Plant Care Manual, by George Staby, put out by the Society of American Florists
Postharvest Handling and Storage of Cut Flowers, Florists Greens, and Potted
Plants, by J. Nowak 
and Ryszard Rudnicki,
Timber Press
Specialty Cut Flowers, by Allan Armitage, Timber Press.
Cut Flowers, Prolonging Freshness, by John Sacalis, Ball Publishing, Batavia, IL.