I have grown a lot of Alliums from seed over the years and I found that pricking them out too early was not a good idea (for me at least). I tend to leave them in the seed pots and rather than plant out individually, I put the whole pot into a bigger deeper one and let them grow on until they are a lot bigger. Remember that unlike many plants they do not have branching roots, so if you damage one, it dies and has to be replaced by another from the basal plate. I often wait until the second year, when they have gone dormant before planting individually, especially with the ones which form bigger bulbs.
