I have only just started some off as recommended by a sweetpea breeder. You put the seeds on damp paper, kitchen roll, cover with cling film and wait for the root tip to appear brfore planting singly in pots. Keep the kitchen roll damp buy not soaking.
I grew nearly 500 last year for a family wedding was cancelled so thought I would give them a miss this year. However, I do love them so belately, have sown about 40 seeds. Different varieties seem to germinate at different rates. Last year I sowed the seed in the autumn and grew them on in a cold frames through the winter, strong stocky plants and early flowering. It will be interesting to see how this years effort does, last year was not a good year for sweetpeas.