A 5 week cool period helps germination...
lightly cover seed soil temp 60F night & 65F days for germination taking 14-21 days to germinate... Store in a cold frame overwinter to have flowers next year....
Some species & or cultivars regularly have poor germination and/or vigor

I grew delphinium from commercial seeds via the winter sowing method in 2010 and got lovely, healthy plants that bloomed this year. You might also check Swallowtail Garden Seeds' website--they include seed sowing instructions for all the seeds they sell, including delphiniums.

Freshly harvested Delphinium seed will usually germinate without the chilling requirement of stored seed. Al