Packets of catnip seed
shouldn't be that hard to find now with spring
just around the corner, at least here. You can use a seed
starting potting mix if you like, they usually do a good job cause the 'seed
starting' mixes are essentailly sterile. Catnip seeds
are tiny and should be lightly sowed, by the same token, germination is usually low and erratic at best, so don't be discouraged if only a few seeds
actually sprout. Dampening off will be a real problem, so if you can...try not to over water your seed
tray and keep a little air moving to discourage this and the sterile potting mix will help. Catnip seeds
need a little light to germinate ...so barely cover the tiny seeds
with the mix.
if you need more info, let me know, I'm never sure just how much detail folks really need.
The old adage is holds true for catnip..."if you sow it, cats won't know it". Its only when the leaves are gently bruised the plant releases its essentil oils letting the cat know its close by.