Getting this IDed for a friend. He writes "It is the only example I have ever seen and is on the roadside of Moana Road, Plimmerton. Pretty sure it is a wild brassica of some sort (turnip/radish) of which there are many in the area both yellow and white (?very pale blue) flowers but nothing with this colour - rather striking! Possible mutant? like the rest of us in Moana Road!!!! One photo shows the leaves"
I took a stab and suggested Hesperis matronalis. Sweet rocket.
but apparently the foliage is quite different
Large planted trees with variegated leaves and ripe fruit, and wild seedlings with non-variegated leaves
I'm trying to find what this plant is, so I can get it healthy. I thought it was a night sky rhododendron, but on looking it up, it seems different.
See comments on this obs of the same thing https://inaturalist.nz/observations/70803160