Step 1: This is a direct, factual question asking for the author of a specific poem.
Step 2: The poem "Martha" is a well-known work in English literature.
Step 3: The author of the poem "Martha," which is about a woman who tells enchanting stories, is the English poet and short story writer Walter de la Mare. He was renowned for his works for both children and adults, often with themes of fantasy and the supernatural.