Cut flowers need to be well hydrated to last. They should be kept in a cool place, but the water in their vase right after they are cut should be warm.
Right after Cutting
Flowers absorb warm water better than they absorb cool water. To ensure maximum hydration, place them in a vase filled with water that is about 43.3 degrees Celsius, about the temperature of bath water. Then place them somewhere cool for an hour or two.
Storing flowers at about 1.67 degrees Celsius will keep them fresh longest. Cool temperatures minimise water loss and slow development. Any temperature above freezing but below 40 or 10 degrees Celsius will work well. If the flowers are being displayed in a room warmer than that, putting them in the fridge or another cool place at night or whenever they are not being displayed will prolong their vase life.
Storing flowers in a fridge full of fresh produce may decrease their vase life, as fruits and vegetables release ethylene, a ripening hormone that speeds ageing in flowers.