Perhaps one of the most famous and celebrated nature poems of Seamus Heaney is "Death of a Naturalist" - and this poem also gave it's name to the well-known collection by that name. Superficially, the poem details the meanderings of a small boy (who thinks he loves nature) towards a favorite haunt of his in the countryside - a pond. However, on this occasion it seems to be filled with frogs (not a problem usually, but on this day there are more of them and the boy gets up close and personal with the frogs to study them in more detail.) On closer inspection, the boy decides that the sheer number of the frogs makes them appear verminous and threatening and Heaney 'actualises' this with vividly gross imagery and simile techniques ( ie the sound they make plopping into the water, their hideous features etc.) The boy's desire for the idealistic idea of becoming a naturalist dies as he suddenly grows up and recognises the reality of the animal kingdom.
To add to the answer already given, what is very interesting about Heaney is his use of agricultural trope and the landscapes of nature. He seems relate all of that to the vocation of the poet. In Death of a Naturalist, there is a poem 'Digging' where he makes this association very very clear. He calls the poet a digger who digs with his 'squat pen' much like the farmer. He has a collection of poems called 'Field Work' where all the poems, as the title suggests, makes the same comparison between the poet and the farmer. The excavational imagery in Heaney connects with his evocation of the Irish history, Ulster's violent past as in the bog-lands of The Tollund Man.
In a poem like The Father, once again, the poet finds himself face to face with the passing way of agricultural life, associated with the spectral image of paternity, native tradition. Rather than creating a radical break, he will appropriate it.