Nettles
The most significant and obvious symbol in the story is the nettles. The nettles symbolize all the many things in life that are going to eventually hurt and cause pain to the narrator's son. The nettles symbolize all those things which are pose potential threats in society.
Blisters
Blisters develop on the boy's skin as a result of his encounter with the spiky green spears. This is the injury which stimulates the son's seeking his parents for comfort. The blisters are literal, of course, but also symbolize all the various different ways in which he will experience pain in the future.
The Billhook
The narrator sharpens the blade of his billhook in preparation to attack the nettles. A billhook is basically a sling blade that can be swung with a velocity that allows the sharp edge of the steel to slice right `billhook thus comes to symbolize all the many "weapons" parents have their disposal to seek vengeance upon whoever or whatever has hurt their child.
Funeral Pyre
After slicing the nettles so that none no longer stand vertical, the father takes the extra—and unnecessary—step of burning them. Cutting the nettles down has relieved them of their danger since the father can now simply bag them and dispose of them. The fact that he refers to the burning process as a funeral pyre along with the very fact of his needless act makes it a symbol of parental overprotection.
The Tall Recruits
After having disposed of the specific nettles which harmed his child, the father is faced with the reality that they grow back. The growth of new nettles which present the same danger to his child is symbolic of the fact that even the best parents cannot even protect their children from making the same mistake more than once.
