Every summer, goblins leave The Sunless Citadel and come to Oakhurst to sell a ripe, red magical fruit. This fruit seems to be able to heal nearly anything. The goblins also bring a winter fruit, though no one buys it anymore. The winter fruit seems to destroy the health of those who eat it. Attempts to grow fruit from the seeds has thus far failed. The goblins seem to steal the fruit after it grows to a certain height.
Update – Our heroic adventurers now believe that the fruit bushes/saplings uproot themselves and walk away. They believe that the goblins have nothing to do with that. They came to this belief after being ambushed by little stick/bush/sapling creatures in the middle of the night, while camping near the ravine.