Dieter
I have indeed sown exhibition onion seeds this year on January 19th, but the caveat is that I am transplanting them from modules into pots rather than doing what Charles traditionally does and sow five or six seeds in modules.
My Kelsae seedlings will be six weeks old on Friday and the fastest growing showed second true leaves emerging on day 35. This obviously gets the plants to be larger when transplanted outdoors, but without huge indoor spaces, there is a limit to the numbers you can grow. I can do 24, which will be lowered to 18 on Friday as I weed out the weakest six.
I guess an experimental type might sow multiple seeds for clumps in modules in January, then tranfer a dozen to 7.5cm pots around day 21 and keep growing them until transplanting whenever. This would give you around fifty to sixty onions from a very early start.
Obviously, in January and February, growth is slower than in March and April, unless you use grow lights, which I do not have.
The real professional exhibitors sow seeds in November!!