It comes from a Chinese family and all they know about it is I am not sure of its history Dad said that Grandad grew it up in Auckland but doesnt know where it originated from. We pick off the leaves and dry them and then soak the dried leaves in gin (Dutch Geneva). We use it for medicinal purposes the gin mix is used on cuts and bruises and I have also used it on insect bites and bee stings. Mum also used it as a poultice when my husband had third degree burns on his neck and face. The family think it is a fern but it looks more like it Umbelliferea (carrot family)
I'd go with Tanacetum as well, especially given the medicinal properties you've listed. Have you ever seen it bloom? If it really is a tansy, it will have bunches of compact flowers, probably yellow-orange in colour, without any visible or distinct petals.
Gin and tansy is a very old combination, both for drink and medicine, so your family recipe combined with the fact that it looks exactly like tansy bodes well for this ID. Rub and smell the leaves: tansy has a very strong, distinct aroma.
Thank you all you are correct it is tansy (Tanacetum vulgare). I sent the same photo to friends at the main New Zealand herbarium and to Kew and they came back with the same answer. I should have been able to do it myself but I was fixated on the Chinese medicinal aspect and never thought to look in European herbals.
