In "To a Poor Old Woman," which symbolic importance or meaning do the plums take on?

The plums in this poem symbolize comfort and happiness. The old woman is "giving herself" to the plum in her hand which shows that she is completely engrossed in the act of eating it and putting her life into it. Williams also directly says that she is 'comforted' and finds a 'solace' in the plums which show their importance to her happiness.