chelle, how are you growing them? I have a very scientific method that has never failed me. I take a pencil, poke a hole in the ground, stick a seed in it, cover it up, and it grows.
I've never put them at any certain depth. I've grown them all over the country, so I don't think they are all that particular! One thing is for sure though. They like poor soil the best. With good soil, you will get a lot of foliage, but very few, if any, blooms. Also, I've found that they grow best if started where you want them, instead of transplanting them.
Has anyone here ever eaten nasturtium flowers? I haven't gotten up the nerve to try them!