The first six lines of “Death of a Naturalist” establish the poem’s setting and begin to hint at its themes. The speaker spends these lines describing a “flax-dam.” A “flax-dam” is a small pond or swamp that farmers use to soften flax, weighing them down with “huge sods”—heavy lumps of dirt. They leave the flax in the swamp for several weeks, during which time it starts to rot or “fester” (and some of the flax gets left behind and rots there all year). As a result, the “flax-dam” is a stinky and vibrant natural space.
The speaker uses imagery to convey the smell and sound of the place. The rotting flax “swelter[s]” in the sun every day; it releases “Bubbles” that burble up from the depths of the swamp. And bluebottle flies constantly buzz around it. The “bluebottles” hint at some of the complicated dynamics that will unfold over the course of the poem. They are carrion flies that feast on dead and decaying animals and plants. Thus, they are symbols of death. Their presence here suggests how complicated life is: even as the “flax-dam” is a space of incredibly vibrant life, it is also haunted by death.
Further, the “bluebottles” are hard to ignore. They create a sound so loud that it seems to the speaker to be a “strong gauze of sound” in line 6. In other words, this metaphor suggests their buzzing is so powerful that it seems to be a material, physical thing. And the alliterative /s/ sound in the line—“strong gauze of sound around the smell”—is itself powerful, almost physical. It gives the reader a hint of what the “flax-dam” sounds like. Similarly, in line 2, the speaker uses a sharp, queasy assonant /ee/ sound—in “green” and “heavy”—to capture the rank smell of the swamp.
As line 6 suggests, the poem is powerfully alliterative, full of loud, prominent alliterations. These alliterations recall the kind of poetry written in medieval times in England and Ireland—poetry that used patterns of alliteration as its central formal device. The poem is connected to this deep tradition in English-language poetry; it summons that tradition into the present.
At the same time, however, the poem is written in blank verse, meaning it uses unrhymed lines of iambic pentameter. Blank verse is a distinguished, prestigious meter: it's the meter that Shakespeare and Milton used. But the poem's meter is consistently rough. Arguably, none of these lines are metrically regular. Further, the poem's lines often end with alliterations, like "heart" and "headed" in lines 1 and 2 or "sods" and "sun" in lines 3-4. These alliterative pairs aren't strong enough to count as rhyme—but they do serve to remind the reader that the poem could rhyme, though it never quite makes the leap.
Finally, the poem is also highly enjambed. Only lines 4 and 6 are end-stopped here. The speaker favors enjambment for different reasons in different parts of the poem. Here it conveys the energy and enthusiasm of the speaker’s curiosity about the “flax-dam.” And it also suggests some of the complicated feelings that the “flax-dam” will eventually inspire in the speaker. For instance, the poem’s first line, “All year the flax-dam festered in the heart” could be read as a complete sentence in itself—in which case, the state of the “flax-dam” would be a metaphor for the state of the speaker’s heart. The next line makes it clear that the reader shouldn’t take it that way—but the possibility is tantalizing, and hints at things to come in the poem.