The tree and the Night Man collectively serve as the central motif of The Night Gardener. The two are irrevocably linked, and they represent a few things. Together, they embody the book’s theme of The Link Between Desire and Dependency. The tree rises to power because it feeds its own desire for people’s life energy, and the strength it gains from this vampiric act allows it to engulf the gardener who cared for it during his natural lifetime. In the time since, the tree has grown more powerful as the result of absorbing more souls, which it has been able to do thanks to the Night Man’s efforts.

In the legend that Hester Kettle tells in Chapter 31, the gardener begins life as his own person with a lovely garden of flowers. In the reality of the novel, the tree does indeed have the gift-giving ability that the legend ascribes to it; in the legend, the gardener repeatedly asks for eternal life, which the tree grants as long as the man takes care of it. This exchange symbolizes the importance of the old adage that warns to “be careful what you wish for.