Christina Rossetti's poem "A Birthday" uses imagery of nature and objects made from nature to express the depth of her love. In two stanzas of iambic tetrameter, the speaker compares her heart first to singing birds and fruit-bearing trees, and second to an imperishable rainbow shell and an ornate silk structure, saying her love makes her heart glad beyond even these images. The poem celebrates the deep emotions of love that cannot be fully captured by comparisons to nature alone.