Temperature: It's one thing to know the proper storage temperature for a particular crop as listed in this manual. It's quite another to maintain flowers and plants at this temperature. Even if a cooler operates at the right temperature, crops themselves may rest at a different temperature. Thus, proper storage temperatures and effective heat exchange are required.
The cooler temperature should be within plus or minus one to two degrees of the ideal flower/plant storage temperature. Check the average cooler temperature by measuring the water temperature in a five gallon bucket held in the cooler. All coolers should have at least two thermometers to obtain temperature ranges within the cooler. Use one thermometer as a control for the other.
Standardize thermometers at least once per year. A thermometer placed into a mixture of excess crushed ice and water should read 32 degrees Fahrenheit or 0 degrees centigrade.
Relative humidity: Generally, flowers like maximum relative humidity in a cooler. A simple approach is to specify a minimum temperature differential - "TD" in refrigeration jargon-between the coils and cooler air temperature at set point. The smaller the TD, the higher the relative humidity. A good TD is about five to eight degrees Fahrenheit. Coolers with low TDs cost more than the more common ones with TDs in the range of 10 to 15 degrees.
As important as low TDs are to a flower store, the subject is "Greek" to most individuals not in the refrigeration industry. To fully understand the importance of having low TD, discuss this subject with local refrigeration personnel.
Special equipment to add humidity to cooler atmospheres can sometimes be beneficial. Be sure that free water does not develop on the flowers and plants. In addition, if the coils are not matched properly with the humidifiers, the water added will be immediately removed by the coils, resulting in excessive ice formation. Remember, wet flowers and foliage will lead to more disease problems. The trick is to maximize humidity but keep the products dry.
For long-term storage, maintain high relative humidity by wrapping the floral crops in plastic after the products are cooled to their proper storage temperature. Don't worry about the relative humidity in the cooler.
Communicating effectively with refrigeration companies: Refrigeration personnel often use jargon. You need to learn something about refrigeration in order to compare information or bids from competing refrigeration companies. Terms that require special attention are TD (see above), effective BTUs at set point temperature, coil surface area, defrost system (none, timer, hot gas or electric heaters), air exchanges per hour and coolant or Freon type. While knowledgeable about refrigeration, some companies are not knowledgeable about the requirements of floral crops.