when is the best time to re-pot my Cordyline Australis

Hi Carolejayne, you can pot your Cordyline virtually any time of the year though the best is probably just before it's roots comes into new growth in spring so March/April would be fine.

A general slow release feed (preferably a more organic one such as Vitax Q4) applied a couple of times a year on the top of the compost would work well though you could give liquid feeds if you want with a propitiatory feed.