Flowers are a type of plant that many like to cultivate because they are nice to look at. When a flower is growing into full maturity, it is said to be blossoming. The word blossoming can also mean maturing or developing in a promising way. The word blossoming is used here to describe how a business is going. The joke is playing on the word "blossoming" because it describes what healthy flowers do, and a business that shows promise in being successful.
So , how ' s the flower business going ? Oh , it ' s blossoming quite nicely .