"My son aged three fell in the nettle bed."
The opening line of the poem situates the entire "plot" of the narrative. This is a poem that tells a story about a young son who gets hurt after falling into a bed of weeds characterized by sharp, stinging pointy leaves. This is the originating incident which drives everything that follows. It is like an opening sentence in a short story and it immediately alerts the reader to the type of poem that will follow. It will not be an exercise in style and abstract meaning. It will tell a direct story with a clearly defined message or lesson.
"And then I took my billhook, honed the blade
And went outside and slashed in fury with it
Till not a nettle in that fierce parade
Stood upright anymore"
The consequences of the boy's tumble into the nettles blisters on his skin and tears in his eyes. After the boy has come seeking comfort from his parents and received it, the father reacts. His reaction is to treat the weeds as a menacing, threatening entity not unlike a poisonous snake or a stranger with a gun. The nettles, despite their inability to even move on their own, have become a predator seeking the boy as prey. They must be destroyed and the threat overcome and removed. And so, the father's reaction is to take a gardening tool and turn into a weapon. This quote signifies the father's characterization of himself. He is the protector of his family. The dramatic language engaged here—using words such as "slash" and "fierce" and imagery in which sharpening the sling blade transforms it into honing a sword—also serves to raise the question of whether he is being overprotective.
"My son would often feel sharp wounds again."
By this quote, the closing line of the poem, time has passed and much has happened. Although the father has succeeded in destroying the threat to his son, the victory is only temporary. Within two weeks, they have grown back, and their sharp edges once again present a threat. Any doubts that the father has reacted with absurd overprotectiveness are eased with his final thoughts in which he reconciles himself to the reality that he cannot possibly protect his son against all the dangers in the world.
