Who is a person who grows or sells flowers?
A person who grows flowers (ornimental horticulture) is called a
horticulturist; horticulture is divided into a number of
divisions:
commercial horticulture
ornimental horticulture
retail horticulture
public space management
floriculture etc.
A person who sells flowers is normally called a florist, but may
have a background in design or horticulture.