The Renaudière vineyard is just full of these blue flowers right now. The hot dry weather we had for a couple of months must have been ideal conditions for them. The flowers are one of several that are commonly known as cornflowers.
The plant that flowers this way is actually wild chicory. It's closely related to the salad greens that we call "curly endive" and "Belgian endive" in the U.S. Bitter salad greens like radicchio and escarole are also closely related to it. Wild chicory is native to Europe, but has been naturalized in North America, China, and Australia.
By the way, I'm throwing in this photo of yesterday morning's sky over the vineyard because of how blue it is too. I mentioned hot weather up above, but we're in a cool snap right now. It feels almost chilly outside this morning, and yesterday I had to put on jeans and a long-sleeved shirt before I went out walking with Natasha.
Back to the flowers — why are they called "cornflowers"? It's because they grow on the edges of fields of grain, and the British word "corn" just means grain. In America, "corn" is maize, which is also called "Indian corn." In France, the wild chicory plant is called — surprise! — chicorée sauvage. It's also called chicorée amère — bitter chicory — because its leaves have a bitter taste.
In the middle ages, the wild chicory plant was considered to have magical qualities. It was used to blunt or quell the human libido. In other words, it was understood to be an antiaphrodisiac. The French wikipedia article lists 13 varieties and subspecies of wild chicory. One variety gives the chicory that is added to or substituted for coffee.