Till the white tail pops like said above. Plant the tail down into the dirt about 1/4 inch down. Or, just throw the seed in a pot without germinating and it will prob work out fine.
Depending on the maturity/quality of the seed Anywhere from 12 to 72 hours Any longer than that and you may have to scour the outside of the seed and try it again or, you may have a bad seed I have experimented a lot with seed germination GL
How long should the tap root be - sticking out of the shell - before you plant it? I've planted them as soon as the root showed, about 1/8", and the shell seems to 'stick' on the sprout where I have to intervene and pop it off and was wondering if that's because I planted it early?
You did it right. Letting the taproot get longer won't affect the shell popping off or not, but if left to germ too long the taproot could become entangled in the paper towel fibers.