As artistic movements, both Romanticism and Realism spread throughout literary forms across the United States, Britain and much of Europe. While Romanticism refers to a single period in literature, Realism can refer to a specific era as well as a pattern of style that transcends a single time period. Both literary philosophies express themselves differently, especially in poetry.
Availability of Poetry
Romanticism in literature started around 1800 and ended somewhere between 1830 and 1860. The major literary traditions of Romanticism included character sketches, slave narratives, short stories and poetry. Realism, when referring to the official artistic movement occurring between 1855 and 1900, includes very little poetry -- its major literary forms only consist of novels and short stories. When applied as a broader term, however, Realism includes poetry from any era that follows the philosophical tenants of that movement.
Aesthetics
Simply put, both Realist and Romantic poets concerned themselves with external aesthetics, but poems of the Romantic era describe the world as desire dictates it should be, while poems of the Realist tradition describe the world as it actually is. For example, in "Intimations of Immortality From Recollections of Early Childhood," William Wordsworth describes the scenery of his youth as looking like it were "Apparelled in celestial light, / The glory and the freshness of a dream." This presents a standard, dreamy Romantic view. A traditionally Realistic view appears in Shakespeare's "Sonnet 130," when he explains very honestly, "My mistress' eyes are nothing like the sun."
Nature and Society
Romantic poems tend to dwell on sensory experience of the natural world, while Realistic poems describe subjects from contemporary, everyday life, usually focusing more on character than on sensational events. In Wordsworth's "Intimations," he describes natural scenes like "Waters on a starry night" and the trees and flowers in a valley. Shakespeare's "Sonnet 130," on the other hand, focuses on describing a mistress, demystifying the subject by explaining how unlike nature and ideals she appears in lines like "no such roses see I in her cheeks."
Imagination
As a general rule, Romanticism in poetry relies on imagination, emotion and intuition, while Realism in poetry rejects lofty ideals and prefers objective, true-to-life statements over those made using subjective imagination. Wordsworth makes imaginative, spiritual statements in "Intimations," such as "The Soul that rises with us, our life's Star, / Hath had elsewhere its setting, / And cometh from afar." Shakespeare's "Sonnet 130," however, explicitly rejects such imaginative illustrations. In the lines "I love to hear her speak, yet well I know / That music hath a far more pleasing sound," the speaker says that, while he loves his mistress's voice, he acknowledges the truth that her voice does not objectively compare to music.