Simple, the man says! First get your gentians to a size to want to divide them. I have never divided any, Owdboggy, but if I did then I think I would do it in early spring, just as they start to make new growth.

Keith Lever obviously does it by the gillion, but when is critical. I will have to ask him next AGS show, Carleon possibly.
I have three really big pots (12 inch ones) full and they have not flowered well this time. They need repotting ion fresh rich compost with a good dollop of Yak muck underneath.

ooh caerleon in wales? when is that???
My daughter is at Newport uni and we have a brill B&B spot in caerleon. I could kill 2 birds with one stone :o)

Cannot find a show date for it yet, but is is usually in the middle of February. Great for Snowdrops!

ooh that sounds ideal as it will be about 6 weeks since she was home for Christmas. I will have to have a look nearer the time.

Owdboggy - the RHS Encyclopaedia suggests division should be done "in spring." It's no more specific than that!

Gentiana sino-ornata is easy to propagate because it produces numerous small rosettes during the growing season and can be lifted and the rosettes can be pulled apart very gently and potted on into rich lime free soil. It flowers autumn time so do this in Spring.
Gentiana septemfida a July/August flowering plant sets lots of seeds which germinate well ot take thick stem cuttings in May or June using non flowering shoots. Put the cuttings round the edge of a pot of free draining soil.

Great, but Spring is an awful long time, like 3 months. So early, late or middle? At what stage of growth? No leaves? A few leaves?

LOL Sorry don't do exact dates. You must use your common sense and do it when it suits you. See Bb's comment.

Trouble is that when I have tried before, they all died. And these days it is expensive to replace them.

As the weather gets warmer and you see your plant starting to grow, dig it up keeping as much soil around the root as possible. It can be pulled apart to give you two plants. Put one back in the ground or in the pot where it is growing happily and try separating and planting the other half. Sorry for my levity earlier. I did not mean to be unhelpful.

Nor was I being deadly serious. Asked a friend (or did I phone him?) Anyway he says Spring before they begin to grow, ie when fully dormant.
Cheers!

I would still advise you to look for signs of growth to ensure your plant is in tune with the growing conditions and does not keel over and die as your other plants did. I'll look forward to seeing all the new babies.