Ever wonder about the advantage of placing cut flowers in warm water rather than cold water and visa versa? Well, here are some facts that I discovered. Bacteria and fungus grow faster at a high temperature than a low temperature. At every temperature rise of 10C (50F) the growth speed is 3X higher ~ on average. Placing cut flowers in cold water prevents blockage of air that is sucked in from the cut stem that could block the water supply after a flower is cut.
Acidification of the solution is helpful for water uptake. The reason being that most preservatives reduce the pH value of the water. I usually use Floral Life Chrystal Clear, available on-line or at the flower wholesaler. Flower preservative works as a water softener, a pH regulator, promotes water absorption and adds nutrients.
As the water adopts the surrounding temperature, this ambient temperature has significant effect on the evaporation of flowers ( through the leaf). The higher temperature higher evaporation. At ambient temperature 2-4C (35.6 - 39.2F) evaporation is about 1/5 of evaporation at a 20C (68F). Flowers age quicker at higher temperatures and are faster to develop bacteria and fungus.
Some woody stems benefit from cutting "up" into the stem, you can make several incisions into the stem (a cut about 2"long is sufficient) Lilac stems are an example. Other stems such as tweedia, euphorbias are best burned so as not to allow the milky sap to infect the clean water they are to be placed in.
So, it appears that a warm '"bath" is beneficial for our cut stems. Changing the water in the container every other day and making sure that no leaves are below water level are two other things to keep in mind to aid in flower life longevity.