After planting the sapling in a hardwood tree patch found in Fossil Island and waiting for it to fully grow, which takes 5,120 minutes (85.3 hours), the plant will grow into a mahogany tree which can be cut to yield mahogany logs (and grant Woodcutting experience). Planting the mahogany sapling yields 63 experience, and checking the health gives you 15,720. When cut down, the tree will automatically regrow after a period of time. The gardener will look after your mahogany tree in exchange for 25 Yanillian hops.