It’s a passion flower

We noticed this flower growing up the fence in our back yard yesterday. Maria guesses it’s some kind of clematis. I did some online research, but there are about a zillion varieties of clematis, so I wasn’t able to identify it conclusively.

Anyone know for sure?

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Lauri Shillings, whose knowledge of plants and animals never fails to impress me, says it’s a passion flower.

So there.