A game of hide and seek normally ends with a discovery: a laugh, a shriek, a friend tumbling out from behind a bush. Nettle's "Becoming an adult" borrows that familiar shape and then quietly breaks it. The child searches, but what turns up is not a friend at all, and that substitution is the whole poem.
The subject is the moment childhood stops being enough. The poem begins in a garden full of "light" and ends with "the harshness of growing up", and between those two points there is almost no event, only a search. Its central idea is that growing up does not arrive as a ceremony or a birthday. The child discovers it by accident, in the middle of a game, when the people and certainties he expected to find are no longer where he left them. The poem never says who the "hiding friends" are. They might be real playmates drifting away, or they might stand for the carefree self the child is losing. That openness lets almost any reader fill the gap with their own experience.
The construction is plain on purpose. There is no rhyme and no regular metre, only short lines in everyday words, which suits a child's-eye view. The poem opens with a line that reads like a list of keywords, "Child, World, Hide and Seek", almost a map of what follows before the poem itself starts. The child is never named, only "the child", so he becomes a figure anyone can step into.
The best detail in the opening is the word "light", used twice in two different senses. "Light floods the garden" is about brightness. "So light and happy" is about weightlessness, the absence of burden. The repetition makes the two ideas fuse, so that sunshine and carefreeness are one thing. It also sets up the ending, because the opposite of "light" in the second sense is exactly the "harshness" that arrives at the close. The verb "floods" is worth a second look as well. It is generous, but floods are also things that overwhelm and then recede, and that may quietly foreshadow how temporary this brightness is. That is an inference, but the word is a strong choice for a poem about something that cannot last.
The turn comes with the casual "So then", which sounds like a child telling a story and which hides how much has shifted. After it the language begins to circle: "Searches and searches". The repetition imitates the action, and the reader can feel the searching become less playful and more anxious, with the game's rules turning into a real need. Then comes the line break at "But finds instead", which holds the reader in suspense for a moment. In hide and seek, "finds" is the happy word, the point of the game. Here it becomes the cruelest word in the poem, because the child does find something, just not what he was looking for.
The last line, "The harshness of growing up", is the longest and heaviest, and it is the only moment where the poem moves from concrete images to an abstract idea. The garden and the game were things you could see, and this you cannot. Its hard sounds, "harsh" and "growing", also stand against the soft, open vowels of "light" and "floods". Even the pronouns shift: the child's world becomes "his world", as though the loss, once found, becomes personal.
A small speculation about the name on the poem: a nettle is a plant that grows in gardens and stings when you reach into the undergrowth. If the name was chosen deliberately, it fits a poem where a child reaches into a bright garden and is hurt. The poem itself does not mention the plant, so this is only a suggestive echo.
What makes the poem worth reading is its restraint. It does not describe what the harshness is, and it avoids melodrama. A less careful poem might have named the loss. This one trusts a simple game and a single reversal to carry the feeling, although some readers may feel the final abstract phrase tells us what the earlier images had already shown. That is a good question to argue about: does naming the "harshness" strengthen the ending, or does it explain what the silence would have said better?