In "The Possibility of Evil," Miss Strangeworth's roses represent her in a number of ways. First of all, like Miss Strangeworth and the rest of her family, the roses are a constant and historic feature on Pleasant Street:
"My grandmother planted these roses, and my mother tended them, just as I do."
As such, the roses have become a permanent feature of the town, just like Miss Strangeworth herself. She has never left the town nor does she ever intend to.
Secondly, the roses look sweet and appealing, just like Miss Strangeworth. "Massed" along the outside of Miss Strangeworth's house, the roses are so pretty that people come from outside of town to admire them. Moreover, wherever they are planted or picked, they leave a sweet smell. Miss Strangeworth, too, has the appearance of being sweet and attractive: she has a "pretty little dimple" on her face, for instance, and "blue eyes." Wherever she goes, people greet her enthusiastically because she seems so sweet and innocent.
Appearances, however, can be deceptive and, just like the thorn of a rose, Miss Strangeworth has a dark side which is expressed through her desire to rid her town of evil.