Thanks wow - it is, apparently, coriaria arborea its twigs are used for making a blue-black dye.
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Grandmother = Tutu Wahine - more formally Kupuna Wahine.
Grandfather = Tutu Kane - more formally Kupuna Kane


In Maaori, tipuna wahine and tipuna taane respectively, but granddad is always Koro, and granny is almost always Nan