Since the vine-like plants encompass the entire island and impede the progress of the boys as they explore the pink granite mountain on the island, they may possibly be symbolic of the difficulties that the boys will experience now that they are without adults and must fend for themselves. Like the extending vines, the conflicts that will develop among the boys may lead to a spiritual descent that will later, like the creepers, encompass the island and impede the existence of order and civilized behavior.
That the feral pig is discovered and entangled in these creepers is further indication of the evil import of these entangling vines. For, others may easily become entangled in pervasive evil and savage ways as their absence from civilization extends in the continuing narrative of William Golding's Lord of the Flies.
The creepers in the novel "Lord of the Flies" by William Golding represent,among other things, the choking weeds of the parable in the christian bible where the good news fell as seeds on the ground and were strangled by the weeds of sinfulness. The creepers are strong, sinuous and strangling - like the propensity for naughtiness or even evil within the personalities of the boys. In the same way that the creeping weeds strangle the beauty of the island, the boys' initial efforts to be good and to get organised and share jobs nicely are choked by their own apathy, laziness and selfishness - they just want to have fun. Like the snake in Adam and Eve, the creeping anarchy destroys the boys chances to save themselves both practically and spiritually from harm and evil instead of choosing the good path.
Well it means that they represent the choking weeds and the christian bible where the good news as the seeds fell on the ground. That what it means.