The central theme of the poem is the sense of unending grief that is felt when someone we love dies.
MacCaig creates a tone that is almost nihilistic and utterly hopeless in its despairingly bleak outlook.
Nevertheless, there is an occasional glimpse of optimism and beauty contained within the image of the crocus, which is
never carved more gently/ than the way her dying/ shapes my mind.
This seems to imply one of the abiding effects of his grief is that it will forever and indelibly continue to shape and impact on his creative work.