James Michener's novel Alaska has a chapter narrating the events of Vitus Bering's 2nd Kamchatka expedition (1730s to 1740s).
In the story, a number of sailors fall ill with scurvy. German naturalist Georg Steller, who accompanied the expedition, finds a kind of grass that he describes as an antiscorbutic[1]. He makes a sort of tea by boiling the grass and urges the (Russian) sailors to drink it. Most refuse, saying, "No German is going to make me eat grass" (roughly -- I don't have the book with me now). And so many of them die of scurvy.
In the real world: I know that Steller did accompany this expedition. I also know that the expedition had a serious problem with scurvy. It killed a number of people, including Bering himself.
But what about the rest? Did Steller really know how to cure scurvy with boiled grass? (It is my understanding that effective scurvy preventives and treatments were not established until around 1750.) Is it likely that sick crew members refused the treatment -- and died as a result -- simply due to nationalism?
[1] Antiscorbutic means preventing or treating scurvy. Today we would say that the plant contains vitamin C.
In the 1993 translation by Frost, Steller states in his journal: "Although I now brought up that fact and asked for a few men to gather up as many antiscorbutic plants as we would need, the gentlemen scorned even this proposal, so valuable to themselves and for which they should have thanked me."
Now, this is on Nagai Island, in August 1741, before the St. Peter wrecked, stranding the Bering expedition, and before Bering dies.
Steller's actions took place before Dr. James Lind's controlled tests regarding scurvy (those beginning in 1747 and published in 1753), but it wasn't until 1795 that the Royal Navy began prescribing lemon juice to crewmen.
How did he come across this idea? Dean Littlepage, in Steller's Island: Adventures of a Pioneer Naturalist in Alaska, states it succinctly:
"In his time with the Itelmen and other Siberian people, Steller had learned how to prevent or treat the disease. With his quick mind, he could not have missed the sharp differences between the indigenous diet and propensity for the disease and that of the members of Bering's expedition. The Native people he had studied ate a diet of mostly fresh food, tilted strongly at times toward pure meat and fat, and they never contracted scurvy; the Europeans ate mostly flour, grain, and dried meat, and during their explorations of the Russian Arctic during the Second Kamchatka Expedition, they died of the disease like mosquitoes in a hard freeze."
Now, there are a lot of problems with taking Steller's account at face value, as Littlepage does. It's important to note that Steller wasn't the expedition's doctor, and his journals and letters are extremely self-serving. He may be taking credit for the actions of others, specifically Mathias Bet'ie (also spelled Betge) who was the expedition's physician.
As Lydia Black writes in her book, Russians in Alaska: 1732-1867, "The journal was compiled by Steller in Kamchatka upon the expedition's return. The available logs are often in disagreement with Steller's assertions."
I have not read Alaska, but I have read about Michener and he did extensive and excellent research for his novels
That aside, one of the prescribed cures for scurvy was called scurvy grass, or what we today call cochlearia, which is indeed rich in vitamin C. Cochlearia is quite tolerant of salt-water and thus can grow in cold climates. It is found in Alaska, so it would be a very likely cure for scurvy in such a book.
I research late 17th/early 18th century sea medicine and it was used for that purpose at least as far back as the printing of the first English sea surgeon's manual in 1617. (John Woodall's the surgions mate.) As you say, the cure wasn't really understood, yet many, many surgeons from the era suggested the problem was dietary and multiple books recommended vitamin C rich foods as part of the cure. (Of course, they also recommended a lot of other things that were absolutely useless in curing scurvy. Most took a sort of 'throwing darts' approach to the problem and hoped one of their medicines would work.)
An excellent book on the topic if you are interested in its history is Stephen R. Bown's Scurvy: How a Surgeon, a Mariner, and a Gentleman Solved the Greatest Medieval Mystery of the Age of Sail, Thomas Dunne Books, New York, 2003.
I also discuss it on my webpage using books from around and before the time period of interest as references: