Late last summer, I divided a large mat of Bolax gummifera by carving divisions with a knife and them lifting out the chunks with a spade (digging down deeply so as not to disturb the roots). The divisions and the original plant were fine afterwards, and appear to be fine now... from what one can tell at this time here, anyway (it's very early spring). It's a very tough plant, though I can't say how it may act in vastly different zones and climates.