I generally agree with the answer already given. This episode with the candlebuds is the first time we see these three boys together, and their reactions to seeing this plant are indicators of their behaviors for the rest of the novel.
Simon, the more sensitive one, sees the flowers and appreciates their beauty. He doesn't want anything from them; he simply sees them and takes them at face value. They are beautiful, and he appreciates that about them. This is the same attitude he has toward the other boys on the island.
Ralph, on the other hand, looks at the plant and sees neither beauty nor usefulness. He is dismissive of them--just as he was of Piggy down on the beach. Ralph is practical and rather self-absorbed; he sees things only in terms of their usefulness to him.
Simon has the most extraordinary reaction. He lashes out at the flowers, as if beauty were evil and must be destroyed. His pride has recently been wounded by the vote for leader, and clearly this is a response born of that hurt and frustration. His behavior is a precursor of things to come--wounds both big and small with little or no thought for how his actions might impact others.
This is a simple incident packed with implications and foreshadowings for the rest of the novel.