We are going to try seed onions this coming season and wondered when people think its the best time to put the seeds in small modules?
I do seed and sets.. Seed I scatter sow early Jan into large trays and heated propagator till they are a couple of inches high. Then just open in the conservatory then into the greenhouse about mid-end Feb'ish and leave till they are at least 2-3mm in diameter before planting out in Spring - normally mid March'ish. My early sets I plant into modules in mid Feb and plant out mid March when i also plant the rest of the sets as a normal main crop.
You can also do individual modules with 2-4 seeds each in Jan/Feb then just leave the strongest one after they are about 4" high. Then plant out in March.
You can do as gavinconway does or sow on Boxing day 26th Dec. This date is a good starting point for lots of onion seed growers.