Gentian Plants have a reputation for being difficult to grow, one possible cause being that different species prefer different combinations of soil and drainage. Most of the spring-flowering varieties, for example, are tolerant of lime, while all the autumn gentian plants loathe it. So if you are to divide your gentian plants, make sure that the divisions also go into a similar soil and growing conditions.
The most popular autumn gentian is Genti-ana sino-ornata, and if this is your plant, you can treat it just like any other rockery perennial. After flowering in the autumn, the gentian plant dies back and becomes dormant through winter. You can lift and divide at any time during this dormant period, but it is best to wait for the first signs of life in early spring. Then you can make sure that each division has at least one good, strong bud.
The gentian clumps usually divide naturally. If they don’t, cut them with a sharp knife. Afterwards, plant the divisions immediately, because if the roots dry out the gentian plants will have a struggle to get established.