Not sure what you mean by 'Papakowhai' variant (?). Sophora chathamica in the North Island is common from Te Paki to Tongaporutu and Waihi thence absent until Porirua (with a few tree's on Matiu / Somes). There are also trees at the northern end of the West Whanganui Inlet, NW Nelson and, so I am told, on the Otago Peninsula. The species is also present on Rekohu (Chatham Island). The jury is out as to whether its truly indigenous around Wellington, NW Nelson and the Chathams - the Otago population is a little odd (and may not be S. chathamica s.s.). Does this answer help?