Flowers & Seasons
#1 Plum plum #1 Winter winter
#2 Orchid orchid #2 Spring spring
#3 Bamboo bamboo #3 Summer summer
#4 Chrysanthemum chrysanthemum #4 Autumn autumn

The little Chinese Character beside the number is the key! The only problem is almost every manufacturer has their own interpretation of the character, we will call that "artistic privilege". Keep in mind that there are several ways to write a character in China, usually it has to do with the media but there is also an old style and a new style. Sets were made in other countries as well, so if your tiles don't match these symbols - there is part of the explanation. The Chinese were also known to put political statements on the flower and season tiles, these sets are very rare and usually the Bone & Bamboo sets.

If you have "scholars" or "travelers" - make those your seasons. If you have two sets of people tiles - just designate which is which. 
For those who have sets with very ornate or very simple designs ... trying to decide if they are the traditional flowers may be more than you want to worry about.