I've just started my leeks (Musselburgh plus another that I can't remember) in seed trays for next year's crops. Seed trays aren't ideal, but I never have any decently deep enough container and if I plant them directly onto allotment the horsetail will hide them within weeks and I'll never see them again!
I usually put some in early (i.e. Jan/Feb) and then plant a few more in seed trays in March/April if I'm not too busy doing other seeds. Sometimes they get pot bound if I'm busy, but it's never had a disasterous effect. I've tried growing 'earlies', 'midseason' and 'late' varieties, but to be honest never noticed any difference in their picking season so now I stick to one or two types. I keep them in a cold greenhouse, sometimes transplanting them into bigger seed trays, until around May when they are big enough to survive the weed onslaught. Yes they do take up valuable space on the plot for a long time of year, but with a family of 5 we get through a lot of them over winter and together with purple sprouting, cabbage and our stored squash they make up our staple veg for the winter months.
I don't prepare our soil at all and our plot is quite exposed. They just go in wherever there's space and wherever I've managed to tame the weeds a little. Did a lot of hand weeding last year cos I entered an allotment competition and I think the leeks benefitted from this. They don't seem to cope well with competition.
Still pulling last year's leeks - they tend to stand quite well here and although some will try to go to seed depending on the weather, mostly they've been ok. They suffered a little from rust and had a spot of white rot (probably from the cheap onion sets I planted) this year, but most of the leeks survived and considering the atrociously wet summer we had I thought they did pretty well.
