The boys are exploring the island at the end of the first chapter when they begin scrambling down a rocky slope. They pause to note the curious bushes that grow here, and Simon says they look like candles. Native to the island, unlike the boys, the bushes seem to cower from the intrusion of humanity:
The bushes were dark evergreen and aromatic and the many buds were waxen green and folded up against the light.
Jack "slashes" at one with a knife and then notes that the boys can't eat them.
The reader learns two things about Jack here. First, he is solely focused on obtaining things from the island for human consumption, no matter the cost. Even though the bushes are not consumable, he still feels the need to destroy them. This quest for destruction will intensify throughout the novel.
The flowers also look like candles, which are typically used to provide light. Light is equated with knowledge and goodness, and Jack lashes out to destroy this. Symbolically, he therefore seeks to live in darkness, eliminating all sources of knowledge and goodness from the island. Again, this theme will continue to develop as the plot progresses.