Autumn sown seedlings and Larkspur failure!

A week ago I sowed some hardy annuals for the cut flower border next year.  Germination has been quick. The cornflower ‘Black ball’ were up first closely followed by godetia and sweet peas; which I chipped a small section of skin from the seed with a sharp knife, the result a 100% germination. The nigellas, cerinthe, wild carrot, ammi, florists dill, bupleurum rotundifolium were close behind. My only failure larkspar, this is a re-occurring problem, I have tried to sow larkspur seed in a variety of ways including; freezing the seed prior to sowing, in and out of propagators and at different times of year. On average I manage one plant a season, an appalling result which would generally result in me accepting defeat and not bothering again. But not larkspar, I am dazzled by the dark blue aura it emits, reminiscent of Jardin Majorelle in Marrakech that I long to visit. So yet again I try my luck with larkspar seeds. Any tips for success would be very much appreciated.

Autumn sown seedlingsAutumn sown seedlings