What is theme and the meaning in the short story, "The Chrysanthemums" by John Steinbeck?

The theme is the general idea or message about human nature or life that a story can convey.

The meaning stems from how details in a story are used to express the overall theme/general idea of the story. 

Often works of literature include many themes and meanings. It adds to the richness of the text.

One theme of "The Chrysanthemums" is passion.

Elisa has a real passion for gardening. She takes great care and time in growing her Chrysanthemums.

When "the tinker" comes by, she feels that he understands her passion when he expresses interest in her gardening skills and her Chrysanthemums.

However, "the tinker" is exploiting her passion to his advantage. She eventually lets him fix a few pots, thus giving him business.

Later as she travles down the road with her husband, she sees the Chrysanthemums she gave "the tinker," tossed on the side of the road. 

While her passion for gardening is still intact, the idea of a connection with someone she felt understood her passion, is gone.