Posted: 09/12/2011 at 14:55
I would still do it now as soil is still warm here anyway while plants are dormat !
But get a move on
As to when, the broad rule is that perennials that flower in the first half of summer (ie before the end of July) are divided in autumn - allowing them plenty of time to recover. Similarly late-summer or autumn performers aren’t divided until spring. Split them just when as new growth is beginning to get going.