Dylan Thomas's "Poem in October" was written in Swansea, where he was born, and is a reflection on his birthday. A central theme in this reflection is the profusion and fecundity of nature, and the connection of this place to not only his youth but also the wellsprings of his poetic imagination.
The speaker gives a sense of profusion and richness of nature by enumeration and amplification, listing different aspects of nature as it is revealed in different seasons, and replete with concrete details.
The next major technique Thomas uses is an incantatory rhythm, which is especially obvious if you listen to a recording of his reading the poem aloud. His stanzaic forms, derived from traditional Welsh poetry, create a dramatic musical pattern, emphasizing the rhythms of nature.
Thomas uses alliteration (repetition of consonant sounds) quite frequently. An example would be "heaven/ Woke to my hearing from harbour." This gives a sense of of the connection of different natural elements within the poem, linked together by sound and suggests that poetic consciousness is a matter of creating a language that reproduces in the human imagination the interconnectedness of the natural world.
Thomas's use of compound adjectives such as "mussel pooled and the heron/ Priested shore" emphasize the permanence of certain aspects of nature. If you say "there is a pool filled with mussels on the shore", you emphasize that this is something true now, but which might not be true at another time, but "mussel pooled" suggests that the pools filled with mussels are part of the inherent and permanent nature of the shore.