Water: Hard water, like tap water, is regularly used in a vase solution for cut flowers. Hard water contains minerals which make it alkaline. Alkaline water does not move readily through cut flower stems and can substantially reduce vase life. One can overcome this problem by using distilled or de-ionized water or by acidifying the water. Commercial flower preservatives usually contain enough acid to acidify most hard water.
Cut flowers have a high surface-to-volume ratio. As such, they lose moisture much more readily than many other perishable commodities. To prevent this loss, keep flowers at a relative humidity above 95%. This micro-climate could be maintained by applying a fine mist with a squirt bottle and keeping flowers away from heated surfaces or open lights.
Cut flowers readily wilt but can be rehydrated without difficulty if there is no obstruction to water flow. Water moves through whole plants by a negative pressure generated by evaporation of water from the leaves. When cut flowers do not take up water, the cause can usually be traced to one of the following: air embolisms, poor quality water, bacterial plugging, and physiological plugging. Water is transmitted in the stem via very fine tubes and is always under tension. When a stem is cut, tension is released and a small bubble of air ¡V an embolism ¡V enters each conducting tube. These bubbles lodge near the cut and will restrict water flow to the flower when it is placed in a vase of water. There are three ways to remove embolisms: (i) hold stems under water and remove about one inch; (ii) acidify the vase solution to pH 3.2 - 3.5; or (iii) heat the vase solution to 104„aF.
Shelf life of cut flowers can also be improved by adding sugar to vase solutions. However, sugar enhances growth of fungi and bacteria, but these organisms could be controlled by inclusion of a couple drops of bleach into the solution. Fungi and bacteria, as well as substances they produce, can rapidly clog the fine tubes of the water conduction system. For this reason, it is important that flower vases be cleaned regularly and that vase solutions be treated with biocides ¡V chemicals which prevent growth of micro-organisms.
When a flower stem is cut, the cells at the cut end may attempt to close (suberize) the wound. In nature, this response might help prevent infection; but in cut flowers, such physiological plugs can restrict water flow and thus shorten vase life. Regular recutting of stem ends prevents the suberization effect.
Temperature: Flowers are alive even when excised from the mother plant. Like animals, they need to breathe or respire. The respiration rate of a product determines its transit and post harvest life; the higher the temperature, the greater the respiration and vital heat increase. Reducing the flowers¡¦ temperature dramatically reduces respiration, growth and aging. The optimum storage temperature for most commonly cut flowers is close to 32„aF. However, chilling sensitive crops such as anthuriums, tropical orchids and ginger flowers cannot be kept below
50„a-54„aF.
Food: Many flowers are best harvested at the bud stage. Stored starch and sugar from leaves and petals provide the energy for flower opening. This is why good growing conditions, proper nutrition, and high light to build food reserves are so important to post harvest flower quality. Quality and vase life of many flowers can be further improved by supplying more food ¡V sugar ¡V after harvest. Sugar is routinely used to open bud-cut flowers before distribution and is included in most flower preservatives.
Ethylene gas: Ethylene gas is a naturally-occurring plant growth regulator produced in high concentration by ripening fruits, vehicle exhausts, and cigarette smoke. However, certain flower crops, especially carnations, die rapidly if they are exposed to minute concentrations of ethylene gas. Therefore, arrange flower positioning to minimize ethylene exposure. Ethylene effects can also be prevented by holding the product at low temperatures and by treating very sensitive commodities (carnations) with silver thiosulphate salt (STS).
Maturity and Harvest: As mentioned previously, many cut flowers can be harvested in the bud stage and opened after storage. Buds, of course, must be physiologically mature. At that stage, harvested buds can be opened fully and have a satisfactory display life. Flowers should be harvested in the early morning when temperatures are lower and plant water content is high. At no time should you place flowers on the ground. Such a practice is a fruitful source of bruising and fungal infections.
Handling: The most important key to quality maintenance of cut flowers is careful handling; Tender Loving Care! Bruising and other mechanical damage not only detract from the appearance of the product but are good avenues of entrance for decay organisms.
