Ted Hughes's "The Laburnum Top" is a poem about the cycle of life. It begins, in the first stanza, with a description of a tree in autumn. Some of its leaves are turning yellow, and its seeds have fallen. This represents one life fading and another, in the form of the seeds, about to begin.
In the second stanza, a goldfinch arrives with "A suddeness, a startlement," and the tree is brought back to life again. Its branches become busy with "chitterings, and . . . tremor of wings, and trillings," and the entire tree "trembles and thrills." The tree is also described, metaphorically, as "the engine" of the bird's family. In other words, the tree helps the bird and its family to flourish and, as it were, move forward. It provides the bird, and its family, with a place to rest and find shelter. It also provides food, in the form of sap and buds, for example. This stanza represents the co-dependency of life. One life, even (or perhaps especially) when it may be fading, helps another. The old life helps the young life by providing for it, and the young life in turn helps the old life by revitalizing it.
In the third and fourth stanzas, the goldfinch flies away, "towards the infinite," and the tree dies, or "subsides to empty." These stanzas represent death. This ending to the poem also perhaps suggests that there is a spiritual side to life. Indeed, the bird may symbolize the soul of the tree, which animates life (the tree) for a short while and then leaves to return to "the infinite." Without the soul, life, like the tree, is "empty."