Sowing seeds question

Hi sorry for the elementary question but can you sew seeds indoors any time? I bought some delphinium seeds a while ago (Pacific Giant and High Society). I had put some outside, nothing happened. Packet says sow indoors up to end May. Can I still do it now? Says 21-42 days to sprout but it also says no flowers until next year. That's a long time. I had also sown some California poppy seeds outside ages weeks ago and nothing has happened. When I say sowed, I just threw them around on the bedding areas and covered them a bit. I figure I am better off doing it properly indoors in a seeding tray. Is it too late or can this be done any time to get flowers this summer? I'd buy the plants but I haven't seen delphiniums anywhere :-(