The image of her aging mother - ‘pale as a late winter’s moon,’ -- conveys the fragility and the inevitability of aging -- highlights the physical changes brought by time and evokes a sense of gentle, serene decline rather than abrupt decay.
The image with the vivid, lively description of young trees sprinting and merry children spilling out of their homes --- contrasts sharply with her mother's stillness and silence --- enhances the sense of her mother's isolation in her old age / the relentless passage of time that spares no one -- life’s transient nature.