Answer: The plant we grow as an annual would actually be a perennial in a warmer climate, so perhaps this is what your friend is thinking of. It can also self seed and seem like a perennial when in fact there are new plants in the same place each year.
It is also possible your friend is simply thinking of a clematis vine. There are many white flowered varieties, however they would not be night blooming like this.
I'm sorry I don't know of an exact duplicate that would be hardy.
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