For a couple of years now, I have pre-germinated most seeds in a damp cloth inside plastic bags in the airing cupboard, because I have had so many failures when sown directly into ground or pots. I haven't done the sums, but there are always a few (or a lot) that never sprout. If a proportion of seeds in the packet sprout and grow on healthily when put into gutters or pots or open ground, then there must be something wrong with the rest.
There are problems with this method, especially early in the year, when time constraints or weather make it impossible to get the sprouted seeds into soil until too late (roots tangled and snapping off when handled). The advantages outweigh the problems, in my opinion, and save all that frustration when you have sown a long row of something, watched it keenly, and found nothing happening, or scrappy groups of seedlings.
It also eliminates thinning out seedlings, which I hate doing, and is ultimately more economical.
