The narrator of this poem, which is written in two quatrains, describes a corner of the farmyard in which tall nettles cover old farm implements and suggest that he likes it because it is a reminder of mutability (liability to change) and the transience of life.
The first stanza tells us that the nettles tower over the implements, except for the roller handle, as if they want to assert the supremacy of life and hide the fact that even things made from the most obdurate materials are subject to change and will eventually disappear. Yet it is implied, the nettles grown in spring and will die in due course and what is now hidden will be revealed once again.
The words "cover up" mean the nettles "grow over" but also imply "attempt to conceal".
The stanza also poses the paradox that truth can be revealed through illusion. The illusion here is that life is triumphant, as we know that the implements are lying under the nettles and will be revealed once again when the nettles themselves die - and the illusion will be revealed for what it is also.
The "panting" assonance of the short -u- vowels in "cover", "done", "rusty" and "butt", together with the frequent pauses between the items in the list, covey an impression of exhaustion and reinforce the notion of something that is moribund or very near death.
In the second stanza, the narrator explains why he likes this corner of the farmyard most. He tells us that he likes the dust of the nettles - a reminder of mortality - which is never finally removed although temporarily washed off by the showers that may briefly refresh but otherwise make no difference at all (it is an illusion that they do).
He makes it clear that he has unnatural liking for death by saying that he also likes the bloom (covering of fine powder, here representing the fullness of life) on flowers. However, the yoking of "bloom" and "dust", and the dismissive tone of the word "any", suggested that he knows the bloom will disappear also, and the flowers become dust, just as will the nettles when they die.
The longer, more euphonious vowels (I, bloom-prove, flower-shower, sweetness), the inversion of the usual word order in the first line, the mellifluous flow of words, and the repeated admission that he likes certain things, convey an impression of sincerity and warmth, which in turn suggests how much he values the lesson he has learnt from this otherwise neglected and insignificant part of the farmyard.
In this context, then, then it becomes clear that the word "nettles" in the title (nettles are a stinging plant) is ambiguous and refers not only to the plants that are covering the implements but also to the principles of mutability and transience which is hidden by the nettles, and which people find hard to contemplate because it is not easy to accept the inevitability of death.