Just wanted to comment on my experience splitting my pulmonaria. I did one last summer and it was a very tough and itchy project. I just did another one Monday and it was soooooo much easier. I did use a knife this time to help split instead of pulling apart with my hands and ripping things to shreds. The dirt was moist and easy to dig instead of later in the season when it gets much harder. But the biggest plus was the only leaves were the short tiny ones on the stalks that bloom. mind you they still irritate, but I didn't have to beat back the full sized leaves to see where to split and again when setting them in the new location. I know - some of you will say 'then wear gloves silly', but I just love the feel of the dirt ect and work mostly without them.
Short version - split in spring.