Inheritance
This poem focuses strongly on what the speaker has inherited from his father and his grandfather. Their work ethics and consistency stand out to him the most; he thinks of how long his father has been doing the same thing over and over, and the strength with which his grandfather dug. When the speaker says he has "no spade to follow men like them," his voice is tinged with sorrow. Yet he feels he has inherited the spirit with which they dug, even if he has chosen a different path. He tries to liken writing to digging, perhaps because breaking away from the tradition makes him feel like an outsider, like he cannot fully understand his father and grandfather. This poem is his attempts to tie himself into his heritage.
Work
Work might be the most important theme in this poem. The speaker focuses on his own craft, as well as the crafts of his father and grandfather. He distinguishes between the different types of digging—for flowers, potatoes, or peat—and much of his language expresses the strenuous nature of the farming work. The speaker does not spend as much time explicating his own craft, but that may be because the poem itself is meant to be evidence of his skill as a writer.
Sustenance
Sustenance appears as a significant theme in this poem. Since his father and grandfather dig for different things, the speaker focuses more on how the work they did that sustained their families than on the particular objects of their labor (though clearly the potatoes and the peat play important roles in the speaker's memory). The bottle of milk that the speaker brings his grandfather emphasizes the importance of sustenance through sources like food, but the speaker's role carrying the milk tells the readers that family plays an important part in the idea of sustenance: sustaining a family is the goal of work, but it is also the foundation upon which every person builds his or her career.
Manual labor
This poem, though its descriptions of farm work are visceral and precise, portrays farm work and digging romantically. Though the work is clearly strenuous, the speaker does not mention the toll it may have taken upon his father and grandfather. This may signify some oversight on the part of the speaker, but perhaps the speaker deliberately focuses on the work ethic and strength of his family members, instead of the cost of those attributes.
