hello seedmoney,
those are some amazing photographs.
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I dont know about this particular species, but in general mutations to a white form aren`t very unusual. Some of the first garden plants were white mutants of the wild forms, collected by keen eyed gardeners in the wild. Of almost all garden perennials you can get white cultivars. I remember a pic my brother in law took of a wheat field: billions of red poppy and one white poppy among them. So as long as it doesn`t ruin your color scheme I would just watch it for a while.

bye, Lin

Thanks for your kind words, Lin.
I actually prefer this white variant over the regular "blue" ones. Any idea if the white flowered type will come true from seed? The plant in question is isolated from the others.

that depends on their pollination habit/technique, I once had volunteers of a white Centranthus ruber, all of them white as well; clueless about Dianthus though, self-pollination would make that happen,

bye, Lin.