In the green. Most spring flowering bulbs can be planted 'dry' in the autumn but certain species e.g. Snowdrops need to remain moist during their dormant period. They do not store well and are likely to be dead rather than dormant by the time of planting. In which case they either need to be planted freshly lifted in the autumn or 'in the green' in spring i.e. in leaf before or after flowering. Even so they will probably take a year or two to settle in.
The large patch of Snowdrops at the back of the garden has all but finished flowering so it seemed like a good time to dig up a few clumps for propagation purposes. In previous years I have dug clumps up and put them straight in the ground further away to spread them around. This year I will pot them and see how they do. I could separate the numerous bulbs that form each clump but I think minimising root disturbance will aid their growth.