[The Squatter of Amon Rûdh]

Frodo and Sam have a normal, albeit friendly, master and servant relationship at first, but obviously that changes somewhat during the course of LR. In A Long Expected Party, Hamfast Gamgee mentions having been "prentice" to the previous Bag End gardener, Holman. We can presume, then, a more or less formal system of apprenticeships, which would make gardening a trade in the Shire. Actually a family trade, since Holman is Hamfast's first cousin at one remove through his grandfather's brother Halfred. Tradesmen normally expect payment.

It seems that Bilbo was a considerate employer, and he left Hamfast Gamgee some extremely useful items when he departed. It also seems that Bilbo and Frodo after him treated their gardeners with no little respect and consideration, especially deferring to their professional opinions.

Incidentally, there was a chemist's shop in Exmouth (not very far from Sidmouth) in the 1920s and '30s called Holman and Ham. I've often wondered if Tolkien ever saw it on one of his holidays.