If you really wish to know then I suggest you email Clayson Howell ([email protected]) because the initial weeds portion of the NZPCN was procured from Clayson's data base by John Sawyer. In this case Mike is almost certainyl correct, and as I said before, a "first date" in the Flora is not necessarily the first record of a naturalisation - quite often its not - rather it is the first record the flora writer was happy to cite as an ideal example of the plant they were treating. So first dates of naturalisations in the NZ Flora series need to be treated on a case by case basis.