The only Dianella that is indigenous to your region is D. nigra. But beware of cultivated material and plants so labelled sold in garden centres as there are a number of Australian species being sold here and some are incorrectly labelled as D. nigra. Dr Peter Heenan ([email protected]) based at Landcare's Campus at Lincoln and I worked on Dianella, he may be able to help you with your query if you email him.