My new manuscript is historical fantasy with romantic elements set, like The Sergeant's Lady, in the Iberian Peninsula during the Napoleonic Wars.
As is usually the case when I'm in first draft mode, the manuscript is filled with bolded, caps-locked notes to myself to look up some detail before I show it to anyone beyond my circle of critique partners. I'll have my heroine's mouth water over a dinner of roast beef and [SEASONAL VEGETABLE], or an officer arrive with a message from [APPROPRIATE REGIMENT].
One of my recent notes to myself asked me to find a [TREE NATIVE TO PORTUGAL]. I decided that should be a simple enough fact to fill in, so I googled "trees native to Portugal," and started going through the options on the Wikipedia page I discovered. I settled on the cork oak, which I'm pretty sure I mentioned in The Sergeant's Lady, having seen it named in the soldier memoirs that are such a wonderful primary source for the Peninsular War geek. But back then I didn't look up the details. So I did not know that corks come from the bark of the tree, nor that it can be harvested once a decade or so at no harm to the tree, which can live up to 250 years.
Now that I know all that, I'll be thinking of Portugal and my books every time I uncork a bottle of wine.