Beach Vitex (Vitex rotundifolia), or Pohinahina, is indigenous to Hawaii and the west Pacific.
It’s planted in coastal areas such as the one below, because it’s very tolerant of salt, heat, and wind. Posted for Terri’s Flower Hour. See more responses here.
Graham's Island 
That is a wow of a plant with such lovely flowers. Is it good to hold dunes in place?
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Lovely plant
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A beautiful flowering plant, Graham! It reminds me of a similar one we have in our yard, Dalmatian Toadflax, similar leaf pattern but yellow flowers. Nice that the Beacc vitex is salt tolerant!
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