Florist: Some people like to have green carnations on St. Patrick' s Day. But flowers that are naturally green are extremely rare. Thus, it is very difficult for plant breeders to produce green carnations. Before St. Patrick' s Day, then, it is wise for florists to stock up on white carnations, which are fairly inexpensive and quite easy to dye green.
The overall conclusion of the florist's argument is that there are some people who like to have green carnations on St. Patrick's Day.