Cold storage for cut flowers: temperatures
Cold storage is not a pause button. There is a cold band for most flowers, a warmer one for a second group, and a tropical group that cold damages rather than helps.
The Florist Heaven desk / Chapter 2 of 5
The temperature bands, and the exception that matters
Extension horticulture does not give one storage temperature for cut flowers. It gives three bands, because climate of origin decides how much cold a flower tolerates.
UMass Extension gives three reference points for storage: close to 33F for most flowers, roughly 41F to 43F for some flowers including zinnias and gerberas, and around 50F for chilling sensitive flowers. It states that most flowers hold their quality stored near the freezing point at 33F.
UMass Amherst Center for Agriculture, Food, and the Environment, Harvesting and Handling Cut Flowers. Extension guidance on harvest stage, bucket sanitation, and the microbial cause of blocked stems. Written for growers in the northeastern United States, so treat the crop timing as regional.
The same guidance warns that flowers originating in subtropical and tropical regions develop chilling injury below 50F, with symptoms that vary by species and can include darkening or water soaking of the petals and death of the flower. It names anthurium, bird of paradise, heliconia, and certain orchids among those best stored above 50F.
UMass Amherst Center for Agriculture, Food, and the Environment, Harvesting and Handling Cut Flowers. Extension guidance on harvest stage, bucket sanitation, and the microbial cause of blocked stems. Written for growers in the northeastern United States, so treat the crop timing as regional.
Chilling injury does not look like cold damage while it is happening. It shows up later, after the product has left your studio, which is exactly when you cannot do anything about it.
The practical consequence for a wedding florist is that a single cooler set to one temperature is a compromise, and a recipe that mixes temperate and tropical material forces a decision. Holding the tropical material warmer, outside the cooler but out of heat and light, is a common answer, and it is a tradeoff rather than a solution.
What cold is doing for the stem
A cut flower is still alive and still running its metabolism, with no roots to supply it. Everything it does from the moment it is cut consumes reserves and loses water. Cold slows that down, which is why temperature is the single largest lever you have over how long product lasts.
Extension guidance is explicit that as storage temperature rises, respiration and water loss increase and wilting follows, and that removing field heat quickly is a priority. The general rule it states is that the lower the temperature, the longer the flowers last.
UMass Amherst Center for Agriculture, Food, and the Environment, Harvesting and Handling Cut Flowers. Extension guidance on harvest stage, bucket sanitation, and the microbial cause of blocked stems. Written for growers in the northeastern United States, so treat the crop timing as regional.
For a florist rather than a grower, the equivalent of removing field heat is what happens in the first hour after a delivery arrives. Product that sits in a warm van or on a warm loading area is spending vase life you have already paid for.
Humidity, and why the number is a range
On relative humidity the same extension guidance is candid that the literature does not agree: it reports published recommendations ranging from 75 percent to 99 percent, and explains the mechanism, which is that high humidity reduces transpiration and keeps flowers from drying out.
UMass Amherst Center for Agriculture, Food, and the Environment, Harvesting and Handling Cut Flowers. Extension guidance on harvest stage, bucket sanitation, and the microbial cause of blocked stems. Written for growers in the northeastern United States, so treat the crop timing as regional.
That range is worth noticing rather than glossing. When a published extension source reports a spread that wide, a florist blog stating a single precise humidity figure is not better informed, it is just less careful.
What this means in a working studio
Cold storage capacity is the constraint that quietly decides how large a job you can take, because it decides how far ahead you can build. This is the link between a horticultural fact and a scheduling fact, and it is the reason the timeline chapter and this one belong to the same job.
- Get product cold quickly on arrival rather than at the end of the unpacking session.
- Know which items in the order must not go in the cooler at all, before the delivery arrives rather than after.
- Remember that finished pieces occupy far more cooler volume than the same flowers did as boxed stems, which is usually what runs the space out.
- Assume the cooler is the limit on how much you can build early, and schedule the build against that rather than against bench hours.
How build capacity and cold storage interact with a day that has a fixed ceremony time in it.
Read the timeline chapterA note on where this guidance comes from
The source cited throughout this chapter is extension horticulture material written for growers harvesting their own crop in the northeastern United States. The physiology transfers to a florist holding bought stems, and the crop timing and some of the harvest specific procedure do not. Where your supplier, your varieties, or your climate differ, they are a better guide than a fact sheet written for somebody else's field.
Questions this chapter answers
- What temperature should a florist cooler be?
- Published extension guidance gives bands rather than one number: close to 33F for most flowers, roughly 41F to 43F for some including zinnias and gerberas, and around 50F for chilling sensitive flowers. Tropical and subtropical material including anthurium, bird of paradise, heliconia, and certain orchids can suffer chilling injury below 50F. The source is linked in the chapter.
Sources
Every source below was read before it was cited. Where this chapter states a fact it did not derive, it points here.
- 01Harvesting and Handling Cut FlowersUMass Amherst Center for Agriculture, Food, and the Environment. Extension guidance on harvest stage, bucket sanitation, and the microbial cause of blocked stems. Written for growers in the northeastern United States, so treat the crop timing as regional.